JP7613673B2 - Rail vehicles - Google Patents

Description

The present invention relates to a railway vehicle that can improve the accuracy of detecting leakage current.

A railway vehicle is equipped with an electric circuit that converts and outputs the electric power supplied from, for example, an overhead line via a pantograph using a conversion device such as a VVVF inverter or SIV, and operates an electric motor or the like with the output electric power. In Patent Document 1, a current transformer (current detector) is installed at the input position of the electric power from the pantograph, and the current value at the input position is measured by the current transformer. Patent Document 1 discloses that if the amount of change per unit time of the measured current value exceeds a threshold value, it is determined that a leakage current (ground fault current) of a predetermined value or more has occurred in the electric circuit of the railway vehicle.

JP 2012-223020 A

However, because the current value at the input point of power from the pantograph changes not only due to the occurrence of leakage current but also due to the running state of the railway vehicle and the voltage of the overhead lines, the method disclosed in Patent Document 1 has difficulty in calculating the value of the generated leakage current, and there is a problem in that the detection accuracy of the leakage current is low. Furthermore, depending on the location where the leakage current occurs, the method disclosed in Patent Document 1 may not be able to detect the leakage current.

The present invention has been made to solve the above-mentioned problems, and aims to provide a railway vehicle that can improve the accuracy of detecting leakage current.

To achieve this objective, the railway vehicle of the present invention is equipped with at least one of a pantograph that receives power from an overhead line and an on-board power source other than a three-phase four-wire type that generates power for running the vehicle and runs on rails, and is equipped with a plurality of wheels that roll on the rails, a ground wire that is connected to the wheels and grounded, a supply line to which power is supplied from the pantograph or the on-board power source, electrical equipment that is connected to an electrical circuit including the supply line and the ground wire and operates with power from the supply line, and a monitoring device that monitors leakage current occurring in the electrical circuit, and the monitoring device is equipped with a supply side meter that measures the current value of the supply line and a ground side meter that measures the current value of the ground wire.

The power supplied from the pantograph to the supply line may be either DC or AC. On-board power sources other than three-phase, four-wire types include storage batteries, DC generators including fuel cells, single-phase AC generators, and three-phase, three-wire AC generators. The on-board power source may include at least one of a generator and a storage battery, and an adjustment device that converts and adjusts the power input from the generator or the storage battery and outputs it. The railcar may be equipped with only either a pantograph or an on-board power source, or may be equipped with both a pantograph and an on-board power source. When equipped with both a pantograph and an on-board power source, the power supply to the supply line may be switchable between the pantograph and the on-board power source. The ground wire is installed on the railcar and is different from the rail. The electric circuit including the supply line and the ground wire may be, for example, an electric circuit formed via another vehicle connected to the railcar.

The railway vehicle of the present invention runs on rails and includes a number of wheels that roll on the rails, a ground wire connected to the wheels and grounded, an on-board power supply that is a three-phase, four-wire power supply with a neutral wire connected to the ground wire and generates power for running the vehicle, three supply lines to which power is supplied from the on-board power supply, electrical equipment connected to an electrical circuit including the supply lines and operated by power from the supply lines, and a monitoring device that monitors leakage current generated in the electrical circuit and passing through the neutral wire, and the monitoring device includes three supply-side meters that individually measure the current values of the three supply lines.

According to the railway vehicle described in claim 1, electrical equipment is connected to an electrical circuit including a supply line to which power is supplied from a pantograph or an on-board power source, and a ground line to which ground is connected via the wheels, and the electrical equipment is operated by power from the supply line. A monitoring device that monitors leakage current occurring in this electrical circuit measures the current value of the supply line with a supply-side meter and measures the current value of the ground line with a ground-side meter.

For example, if no leakage current occurs in the electrical circuit and all of the current that passes through the supply line (measurement position of the supply-side meter) passes through the ground line (measurement position of the ground-side meter), the current value of the supply-side meter and the current value of the ground-side meter will basically match, regardless of the running state of the railway vehicle or changes in the voltage of the overhead line. Therefore, the value of the leakage current that has occurred to bypass the ground-side meter can be accurately calculated from the difference between the current value of the supply-side meter and the current value of the ground-side meter. Therefore, by measuring the current values of both the supply line and the ground line, the monitoring device can improve the accuracy of leakage current detection.

Note that "the monitoring device can improve the detection accuracy of the leakage current by measuring the current values of both the supply line and the ground line" does not only mean that the monitoring device itself accurately calculates (detects) the leakage current value, but also means that the monitoring device measures the current value used in the calculation so that the leakage current value can be accurately calculated on a server or the like outside the railway vehicle.

The railway vehicle of claim 2 achieves the following effect in addition to the effect achieved by the railway vehicle of claim 1. A pair of coupling parts that can be coupled to another vehicle is provided at each end of the railway vehicle in the rail direction. A supply pull-through line of the supply line is laid between the pair of coupling parts, and an upstream supply line of the supply line connects the supply pull-through line to a pantograph or an on-board power supply. The supply side meter measures the current value of the upstream supply line. As a result, even in cases where the supply pull-through line is connected to another vehicle and current from the other vehicle flows through the supply pull-through line, the current value of the power supplied to the supply line from the pantograph or on-board power supply mounted on this railway vehicle can be accurately detected.

According to the railway vehicle described in claim 3, in addition to the effect of the railway vehicle described in claim 1, the following effect is achieved. A pair of coupling parts that can be coupled to another vehicle is provided at each end of the railway vehicle in the rail direction. The ground wire includes a ground lead wire that is routed between the pair of coupling parts and to which electrical equipment is connected, a collection wire that branches off from the ground lead wire, and a ground terminal part that connects the wheels and the collection wire so that the wheels are at the same potential. The ground side measuring instrument measures the current value of the collection wire. As a result, for example, a current that flows without bypassing the collection wire (current other than leakage current) can be detected collectively by the ground side measuring instrument after it joins at the collection wire and before it is diverted to the multiple wheels.

The railway vehicle of claim 4 achieves the following effect in addition to the effect of the railway vehicle of claim 1. When the difference between the current value of the supply side meter and the current value of the ground side meter is calculated as the leakage current, the difference is affected by the potential difference between the supply line and the ground line. In response to this, the monitoring device measures the potential difference between the supply line and the ground line with a potential difference measurement unit, and uses a potential association means to associate the potential difference measured by the potential difference measurement unit with the current values of the supply side meter and the ground side meter at the time the potential difference was measured. This makes it possible to calculate the value of the leakage current by correcting the difference in the current values of the supply side meter and the ground side meter based on the potential difference, thereby further improving the accuracy of leakage current detection.

Note that associating "A" (e.g., the current value of the supply-side meter and the ground-side meter) with "B" (e.g., the potential difference measured by a potential difference measurement unit) may mean, for example, storing "A" and "B" in a mutually associated state in the same memory, or storing "A" and "B" in separate memories and associating the two based on the measurement dates and times of "A" and "B." Furthermore, calculating a specific value using "A" and "B" may also be considered as associating "B" with "A."

According to the railway vehicle of claim 5, in addition to the effect of the railway vehicle of claim 1, the following effect is achieved. The monitoring device acquires the running state of the railway vehicle (control state of electrical equipment, time, direction of travel, running speed, running position, outside temperature, humidity, etc.) using the acquisition means, and associates the acquired running state with the current values of the supply side meter and the ground side meter at the time of acquisition using the state association means. As a result, for example, if the value of the leakage current calculated from the difference between the current value of the supply side meter and the current value of the ground side meter becomes large only in a specific running state, it can be estimated that a leakage current is occurring in the part where current flows in that specific running state. This makes it easier to analyze the cause of the leakage current.

The railway vehicle of claim 6 achieves the following effect in addition to the effect of the railway vehicle of claim 1. The transmitter transmits data on the current values measured by the supply side meter and the ground side meter to the outside of the railway vehicle. This makes it possible to calculate the leakage current from the current value of the supply side meter and the current value of the ground side meter, and to analyze the calculated leakage current, outside the railway vehicle. Compared to when these calculations and analyses are performed by a monitoring device, it is easier to make the monitoring device smaller and less expensive.

Note that data relating to "X" (e.g., current values measured by a supply-side meter and a ground-side meter) may be the data for "X" itself, or it may be data for a value calculated using "X" (e.g., the difference in current values or the average value of multiple differences).

According to the railway vehicle of claim 7, in addition to the effect of the railway vehicle of claim 6, the following effect is achieved. The monitoring device uses a difference calculation means to calculate the difference between the current value of the supply side meter and the current value of the ground side meter. The transmission decision means decides whether to transmit data related to the difference from the transmission unit to the outside of the railway vehicle based on the difference calculated by the difference calculation means. When the transmission decision means decides to transmit, the transmission permission means allows the data related to the difference to be transmitted from the transmission unit to the outside of the railway vehicle. This makes it possible, for example, to select data useful for analyzing leakage current from the data related to the difference and transmit it to the outside, thereby reducing the frequency and amount of transmission from the railway vehicle to the outside. Also, if data is temporarily stored in the monitoring device before being transmitted to the outside, the amount of data temporarily stored can be reduced, making it easier to miniaturize and reduce the cost of the monitoring device.

The railway vehicle described in claim 8 is a railway vehicle that runs on rails receiving power from a power supply car in a train consisting of a railway vehicle described in any one of claims 1 to 7 as a power supply car. This railway vehicle is connected to the power supply car by a coupling section either directly or via another vehicle, and operates electrical equipment with power supplied from the power supply car via the coupling section. In order to ground the electrical equipment, the vehicle's own grounding wire connects the wheels rolling on the rails to the electrical equipment. In this case, the current passing through the supply line of the power supply car (measurement position of the supply side measuring instrument) is divided into a current passing through the grounding wire of the power supply car (measurement position of the grounding side measuring instrument), a current passing through the vehicle's own grounding wire of this railway vehicle, and a leakage current generated in this railway vehicle or the power supply car.

The vehicle's ground side meter measures the current value of the vehicle's ground wire. This makes it possible to accurately calculate the value of the leakage current occurring in the railway vehicle or power supply vehicle based on the current value of the vehicle's ground side meter and the current values of the power supply vehicle's supply side meter and ground side meter.

According to the railway vehicle described in claim 9, the on-board power supply installed in the railway vehicle and generating power for running the vehicle is a three-phase, four-wire power supply in which a neutral wire is connected to a ground wire that is grounded via the wheels. Power is supplied from this on-board power supply to three supply lines, and electrical equipment is connected to an electrical circuit including these supply lines, and the electrical equipment is operated by power from the supply lines. A monitoring device that monitors the leakage current generated in this electrical circuit and passing through the neutral wire measures the current values of the three supply lines individually using three supply-side measuring instruments.

If no leakage current occurs in this electrical circuit, the sum (difference) of the current values of the three supply side meters will basically be zero, regardless of the running state of the railway vehicle. On the other hand, if leakage current flows through the neutral conductor, bypassing the supply side meters, the sum of the current values of the three supply side meters becomes the leakage current value, and the leakage current value can be calculated with high accuracy. Therefore, by measuring the current values of the three supply lines, the monitoring device can improve the accuracy of leakage current detection.

FIG. 2 is a circuit diagram showing a schematic diagram of an electric circuit of the railway vehicle in the first embodiment. 1A is a graph showing the change over time in the current values measured in the supply-side current transformer and the ground-side current transformer, and FIG. 1B is a graph showing the change over time in the leakage current value. FIG. 2 is a block diagram showing the electrical configuration of the railway vehicle. 4 is a flowchart of a main process executed by a CPU of the control device. FIG. 2 is a block diagram showing the electrical configuration of the leakage current monitoring device. (a) is a diagram showing a schematic representation of the contents of the driving condition ring buffer, (b) is a diagram showing a schematic representation of the contents of the peak detection memory, and (c) is a diagram showing a schematic representation of the contents of the short-term change detection memory. 4 is a flowchart of a main process executed by a CPU of the leakage current monitoring device. 13 is a flowchart of a peak detection process. 13 is a flowchart of an average detection process. 13 is a flowchart of a cycle collection process. FIG. 11 is a circuit diagram showing a schematic diagram of an electric circuit of a railway vehicle according to a second embodiment. FIG. 11 is a circuit diagram showing a schematic diagram of an electric circuit of a railway vehicle according to a third embodiment. FIG. 13 is a circuit diagram showing a schematic diagram of an electric circuit of a railway vehicle according to a fourth embodiment.

The preferred embodiment will now be described with reference to the accompanying drawings. First, an overview of a railway vehicle 10 in a first embodiment will be described with reference to FIG. 1. FIG. 1 is a circuit diagram that shows a schematic diagram of the electrical circuit of the railway vehicle 10.

The railway vehicle 10 is a direct current electric train, and mainly comprises a metal car body 12, a number of wheels 13 that support the car body 12 and roll on the rails 2, and coupling parts 14 provided on both ends of the car body 12 in the rail direction (front-rear direction). Furthermore, the railway vehicle 10 is a powered vehicle that is equipped with a number of electric motors 22 as a power source, and runs on the rails 2 by rotating the wheels 13 with the electric motors 22.

The coupling unit 14 includes a coupler that mechanically couples the railcar 10 to another vehicle to transmit tensile and compressive forces between the vehicles, and an electrical coupler that electrically couples the railcar 10 to another vehicle. Note that in this embodiment, a case will be described in which the railcar 10 is not coupled to another vehicle.

An overhead line 4 is suspended above the rails 2. A high-voltage (1500 V in this embodiment) direct current flows through this overhead line 4 by generating an electromotive force at the substation 6 with respect to the grounded rails 2. Because the metal wheels 13 are grounded via the rails 2, a closed circuit is formed by the substation 6, the overhead line 4, the electrical circuit inside the railcar 10, and the rails 2 when the pantograph 17 on the top of the body 12 of the railcar 10 is raised and brought into contact with the overhead line 4. This allows direct current power to be supplied from the overhead line 4 via the pantograph 17 to the electrical circuit of the railcar 10.

The electrical circuit of the railway vehicle 10 mainly comprises a supply line 18 that receives power for running the vehicle from a pantograph 17, a VVVF inverter 20 and an SIV (static inverter) 30 that convert and output the power input from the supply line 18, and a ground wire 40 that grounds the VVVF inverter 20 and the SIV 30.

The ground wire 40 is connected to the wheels 13 and is grounded. The ground wire 40 includes a ground lead-in wire 41 that is routed between the coupling parts 14 at both ends of the railway vehicle 10, a central line 42 that branches off from the ground lead-in wire 41, and a ground terminal part 43 that connects the central line 42 to the wheels 13.

The grounding line 41 is a portion to which multiple electrical devices including the VVVF inverter 20 and the SIV 30 are connected, and is configured to be connectable to a grounding line provided in another vehicle via the connecting portion 14.

The aggregated wire 42 is a single electric wire for consolidating the current between the grounding wire 41, to which multiple electrical devices are connected, and the grounding terminal portion 43, to which multiple wheels 13 are connected. Note that the aggregated wire 42 may be formed by connecting the grounding wire 41 and the grounding terminal portion 43 with multiple electric wires and bundling the multiple electric wires into a single bundle.

The ground terminal portion 43 is a portion for making all the wheels 13 installed on the railway vehicle 10 have the same potential. By making the resistance value of each electric wire connecting the ground terminal portion 43 and the multiple wheels 13 the same, the multiple wheels 13 have the same potential. This makes it possible to equalize the current values flowing through the multiple wheels 13, thereby suppressing the generation of stray currents due to uneven currents.

In addition, the car body 12 is electrically connected to the ground terminal portion 43, so that the car body 12 is grounded without going through the aggregated wire 42. By placing a resistor (not shown) between the ground terminal portion 43 and the car body 12, the generation of stray currents that are drawn up from the rail 2 to the car body 12 can be suppressed.

Both the VVVF inverter 20 and the SIV 30 are conversion devices that convert and adjust the DC power input from the supply line 18 into AC power and output it. On the input side of the VVVF inverter 20 and the SIV 30, there is provided a positive terminal to which the branched supply line 18 is connected, and a negative terminal to which the ground side electric wire 45 branched from the ground lead line 41 is connected.

A manual switch (S) 46a that opens and closes the electrical circuit in response to manual operation is provided between the ground side electric wire 45 and the ground lead wire 41. As a result, when the manual switch 46a is closed, the ground side electric wire 45 is grounded and forms part of the ground wire 40.

Note that manual switches 46b to 46g, which will be described later, are configured identically to manual switch 46a, except for their different locations. Hereinafter, when manual switches 46a to 46g are described without distinction, they will be referred to as manual switch 46.

By providing the manual switches 46, the insulation resistance of each part of the railway vehicle 10 can be measured (leakage current can be detected) by performing a conventional periodic inspection. Specifically, in a periodic inspection, the pantograph 17 is lowered to cut off the power supply from the overhead line 4 to the supply line 18, and all manual switches 46 are manually opened to disconnect the inspection objects such as the supply line 18, VVVF inverter 20, and SIV 30 from the ground wire 40. After that, a voltage is applied to the ground by an insulation resistance measuring instrument (not shown) connected to the inspection object and the ground part of the ground wire 40 or the car body 12, and the leakage current generated in the inspection object based on the applied voltage is detected, and the insulation resistance of the inspection object relative to the ground part is measured.

Except for this periodic inspection, the manual switch 46 is closed and the pantograph 17 comes into contact with the overhead line 4, bringing the railway vehicle 10 into a powered state. When powered, the VVVF inverter 20 and the SIV 30 operate.

The VVVF inverter 20 is a device that converts the DC power input from the supply line 18 into three-phase AC power, and outputs the three-phase AC power to the electric motor wire 24. The electric motor wire 24 branches out along the way and is connected to a number of electric motors 22, which are operated by the three-phase AC power supplied from the electric motor wire 24.

The VVVF inverter 20 is configured to be able to variably control the voltage and frequency of the AC power it outputs. In response to the control of the voltage and frequency of this AC power, the rotation speed and torque of the electric motor 22 are controlled, and the running speed of the railway vehicle 10 is controlled. Furthermore, during regenerative braking, in which the electric motor 22 is operated as a generator, the VVVF inverter 20 converts the AC power generated by the electric motor 22 into DC power. During this regenerative braking, a DC current flows from the rail 2 to the overhead line 4 via the ground line 40, the VVVF inverter 20, and the supply line 18.

The electric motor wires 24 are composed of a set of three electric wires 24u, 24v, and 24w. The electric motor 22 is a three-phase induction motor that operates on three-phase AC power and has three built-in coils to which two of the three electric wires 24u, 24v, and 24w are connected.

The SIV 30 is a device that converts DC power input from the supply line 18 into three-phase AC power, and outputs the three-phase AC power to the first low-voltage AC circuit 32. The SIV 30 outputs AC power of a fixed voltage (440 V in this embodiment) and a fixed frequency. The SIV 30 also includes an isolation transformer (not shown). This insulates the input side from the output side of the SIV 30. The output side of the SIV 30 is provided with an electric wire 31 that is connected to the grounding line 41 via a manual switch 46b.

The first low-voltage AC circuit 32 is laid between the coupling parts 14 at both ends of the railway vehicle 10 and is configured to be able to supply power to another vehicle via the coupling parts 14. Furthermore, the first low-voltage AC circuit 32 is configured as a set of three electric wires 32u, 32v, and 32w.

A number of three-phase AC devices 15 (a type of electrical equipment) that operate on three-phase AC power are connected to the first low-voltage AC circuit 32 (electrical wires 32u, 32v, 32w). In each drawing, one of the multiple three-phase AC devices 15 is shown as a representative. Examples of three-phase AC devices 15 include air conditioning equipment that adjusts the temperature in the passenger compartment of the railway vehicle 10, an electric air compressor, a ventilation system, and a cooling fan.

The second low-voltage AC circuit 36 is connected to the first low-voltage AC circuit 32 via an isolation transformer 34. The isolation transformer 34 has a primary winding connected to the first low-voltage AC circuit 32 and a secondary winding connected to the second low-voltage AC circuit 36 wound around the same iron core, and the primary winding and secondary winding are insulated from each other. The isolation transformer 34 transforms the voltage of the AC power input from the first low-voltage AC circuit 32 and outputs it to the second low-voltage AC circuit 36.

The second low-voltage AC circuit 36, like the first low-voltage AC circuit 32, is laid between the coupling parts 14 at both ends of the railway vehicle 10 and is configured to be able to supply power to another vehicle via the coupling parts 14. Furthermore, the second low-voltage AC circuit 36 is configured as a set of three electric wires 36r, 36n, and 36t.

The electric wire 36n is connected to the grounding line 41 via the manual switch 46c. Therefore, when the manual switch 46c is closed, the electric wire 36n is grounded, and the grounding line 41 also functions as the electric wire 36n (part of the second low-voltage AC circuit 36). The insulating transformer 34 outputs single-phase AC power so that the potential difference between the electric wire 36r and the electric wire 36t and the electric wire 36n are each 100V. In other words, the insulating transformer 34 converts the three-phase AC to single-phase three-wire AC and outputs it.

A number of single-phase AC devices 16 (a type of electrical equipment) are connected between the electric wires 36r, 36t and the grounding wire 41 (electric wire 36n) on the grounding wire 41 side via a manual switch 46d. In each drawing, one of the multiple single-phase AC devices 16 is shown as a representative, and for example, in FIG. 1, one single-phase AC device 16 connected between the electric wire 36r and the grounding wire 41 is shown as a representative. The single-phase AC device 16 is a device that operates with single-phase AC power converted by the isolation transformer 34, and examples of the single-phase AC device 16 include lighting that illuminates the passenger compartment of the railway vehicle 10 and heaters.

In addition, multiple DC devices 19 (a type of electrical equipment) are connected between the electric wires 36r, 36t and the grounding wire 41 via a rectifier (not shown) on the electric wires 36r, 36t side and via a manual switch 46e on the grounding wire 41 side. In each drawing, one of the multiple DC devices 19 is shown as a representative, and for example, in Figure 1, one DC device 19 connected between the electric wire 36t and the grounding wire 41 is shown as a representative.

The DC equipment 19 is equipment that operates on DC power obtained by converting AC power from the isolation transformer 34 using a rectifier, and examples of such equipment include door opening and closing devices and brake control devices. However, the brake control device is configured to operate on a storage battery (not shown) in case of an emergency.

In the electrical circuits of the railway vehicle 10 described above, leakage current may occur due to deterioration of the insulation resistance of each part. A leakage current monitoring device 80 for monitoring this leakage current is installed on the railway vehicle 10. The leakage current monitoring device 80 includes a supply side current transformer 87 through which the supply line 18 passes, a ground side current transformer 88 through which the ground line 40 passes, and a potential difference detection unit 89 that measures the potential difference between the supply line 18 and the ground line 40.

The supply side current transformer (supply side measuring instrument) 87 and the ground side current transformer (ground side measuring instrument) 88 are both measuring instruments consisting of an annular current transformer through which the electric wire to be measured passes, and measure the value of the current flowing through the pass-through part. More specifically, a current transformer measures the magnetic field generated at the pass-through part of the electric wire by the passage of current, and measures (calculates) the value of the current based on the magnetic field. The supply side current transformer 87 and the ground side current transformer 88 in this embodiment are configured to be able to measure the value of a direct current, but as their configuration is known, a description thereof will be omitted.

The supply side current transformer 87 is passed through the portion of the supply line 18 before it branches off to the VVVF inverter 20 side and the SIV 30 side, and measures the current value A1 at that portion. This allows one supply side current transformer 87 to measure substantially the entire amount of the current value A1 supplied from the pantograph 17 to the electrical circuit inside the railway vehicle 10.

In addition, a supply side current transformer 87 may be placed on each of the portions of the supply line 18 that branch off to the VVVF inverter 20 side and the SIV 30 side. In this case, the sum of the current values of the two supply side current transformers 87 is approximately the entire current value A1 supplied from the pantograph 17 to the electrical circuit inside the railway vehicle 10.

The ground side current transformer 88 passes through the aggregated wire 42 of the ground wire 40 and measures the current value A2 of the aggregated wire 42. This allows, for example, the current that flows without bypassing the aggregated wire 42 (current other than leakage current) to be detected collectively by the ground side current transformer 88 after it joins with the aggregated wire 42 and before it is diverted to the multiple wheels 13.

The potential difference detection unit 89 is a known voltmeter that measures the potential difference (voltage) V1 between the supply line 18 at the position where the supply side current transformer 87 is located and the aggregated line 42 at the position where the ground side current transformer 88 is located. In other words, it can be said that the potential difference detection unit 89 measures the potential difference V1 between the pantograph 17 and the ground terminal unit 43.

Furthermore, in this embodiment, the potential difference between the ground terminal portion 43 and the rail 2 (each wheel 13) is assumed to be 0 [V]. In this case, it can be said that the potential difference detection unit 89 measures the potential difference between the pantograph 17 and the rail 2.

The method of monitoring leakage current using such leakage current monitoring device 80 will be described with reference to FIG. 2 in addition to FIG. 1. FIG. 2(a) is a graph showing the change over time of current value A1 measured by supply side current transformer 87 and current value A2 measured by ground side current transformer 88. FIG. 2(b) is a graph showing the change over time of the value of leakage current generated in the electrical circuit of railway vehicle 10.

The vertical axis of the graphs in both Fig. 2(a) and Fig. 2(b) is the current value [A]. The horizontal axis of the graphs in both Fig. 2(a) and Fig. 2(b) is the time [s]. In addition, in the graph in Fig. 2(a), the change over time of the current value A1 of the supply side current transformer 87 is shown by a solid line, and the change over time of the current value A2 of the ground side current transformer 88 is shown by a dashed line. Note that in Fig. 2(a), the solid and dashed lines in the overlapping portions are shown slightly shifted from one another in order to make the graph easier to read.

When no leakage current is occurring in the electric circuit of the railway vehicle 10, essentially all of the current that passes through the supply side current transformer 87 (supply line 18) passes through the ground side current transformer 88 (aggregated line 42). Therefore, during a time when no leakage current is occurring, the current values A1 and A2 of the supply side current transformer 87 and the ground side current transformer 88 are the same in the graph of FIG. 2(a), and the leakage current value is 0 [A] in the graph of FIG. 2(b).

On the other hand, for example, when only leakage current from the electric motor 22 to the car body 12 occurs and no other leakage current occurs, the leakage current of the electric motor 22 passes through the car body 12, bypasses the aggregated wire 42, and flows from the ground terminal 43 to the rail 2. That is, the current that passes through the supply side current transformer 87 is divided into a normal route that passes through the ground side current transformer 88 (aggregated wire 42) and a leakage current route that does not pass through the aggregated wire 42. Therefore, in the graph of FIG. 2(a), at the time when only leakage current of the electric motor 22 occurs, the current value A2 of the ground side current transformer 88 is lower than the current value A1 of the supply side current transformer 87, and in the graph of FIG. 2(b), the difference between these current values is shown as the leakage current value.

The voltage supplied to the railway vehicle 10 from the overhead line 4 varies depending on the influence of other vehicles connected to the same overhead line 4, the distance from the substation 6 to the railway vehicle 10, and other factors. This variation causes a change in the potential difference V1 between the pantograph 17 and the ground terminal unit 43 (the potential difference of the potential difference detection unit 89), and the current values of the supply side current transformer 87 and the ground side current transformer 88 vary inversely proportional to this potential difference V1, as shown in Figure 2(a). In Figure 2(a), the potential difference V1 at the time the current value was obtained is shown above the current value graph.

Therefore, it is difficult to accurately detect leakage current from only the fluctuations in current value A1 of the supply side current transformer 87 or only the fluctuations in current value A2 of the ground side current transformer 88. However, as described above, by monitoring the difference between current value A1 and current value A2, the value of the leakage current generated in the motor 22 can be accurately calculated even if the potential difference V1 fluctuates, and the detection accuracy of the leakage current can be improved.

In addition, since the leakage current also varies inversely proportionally to the potential difference V1, the graph in FIG. 2(b) shows the corrected (converted) leakage current value (difference Ad) when the potential difference V1 is 1500 [V]. Specifically, when the potential difference V1 is 1500 [V], the difference between the current values A1 and A2 is used as is as the corrected leakage current value. When the potential difference V1 is 1800 [V], the difference between the current values A1 and A2 is multiplied by 1.2 to obtain the corrected leakage current value. When the potential difference V1 is 1300 [V], the difference between the current values A1 and A2 is multiplied by approximately 0.87 to obtain the corrected leakage current value. Therefore, when determining whether the leakage current value has exceeded the threshold value, the determination can be prevented from being affected by the variation in the potential difference V1.

2(a) and 2(b) are used to explain the case where only leakage current occurs in the motor 22, but the route of the leakage current changes depending on the position where the leakage current occurs, and the way in which the current value A1 of the supply side current transformer 87 and the current value A2 of the ground side current transformer 88 fluctuate also changes. For example, it is conceivable that regardless of whether leakage current occurs, the current value A2 is inversely proportional to the potential difference V1, and when leakage current occurs, only the current value A1 increases relative to the current value A2 by the amount of the leakage current.

When only leakage current occurs from the input side of the supply line 18, VVVF inverter 20, or SIV 30 to the car body 12, the leakage current bypasses the aggregated line 42 and flows from the car body 12 to the ground terminal 43 and to the rail 2, just as when only leakage current occurs in the electric motor 22. Therefore, in these cases as well, the value of the leakage current occurring in the supply line 18, etc. can be accurately calculated from the difference between the current values A1 and A2 as described above, and the accuracy of detection of the leakage current by the leakage current monitoring device 80 can be improved.

In addition, if both current values A1 and A2 fluctuate inversely proportional to potential difference V1 and current value A2 drops relative to current value A1, it can be inferred from the measurement results of leakage current monitoring device 80 that leakage current has occurred from motor 22, supply line 18, VVVF inverter 20, or SIV 30 to vehicle body 12 at the point when current value A2 drops.

The three-phase AC output from the SIV 30 returns to the SIV 30 through the three-phase AC device 15 via the first low-voltage AC circuit 32. However, depending on the type of the three-phase AC device 15, some of the three-phase AC may return to the SIV 30 through the grounding lead-in wire 41 and the electric wire 31. If a leakage current occurs between the three-phase AC device 15 or the first low-voltage AC circuit 32 and the vehicle body 12, the AC leakage current passes through the ground terminal 43, the aggregated wire 42, and the electric wire 31 to return to the SIV 30. In addition, if the current value passing through the output side of the SIV 30 increases due to the leakage current, the current value passing through the input side of the SIV 30 (flowing from the supply line 18 to the grounding wire 40) also increases according to the winding ratio of the isolation transformer built into the SIV 30.

Similarly, if leakage current occurs between the single-phase AC device 16 or the second low-voltage AC circuit 36 on the output side of the isolation transformer 34 and the vehicle body 12, the leakage current passes through the ground terminal 43, the aggregated wire 42, and the electric wire 36n so as to return to the isolation transformer 34. Furthermore, if the current value passing through the output side of the isolation transformer 34 increases due to the leakage current, the current value on the input side of the isolation transformer 34 and the output side of the SIV 30 increases, and the current value passing through the input side of the SIV 30 also increases.

In this way, if leakage current occurs in the electrical circuit on the output side of SIV30 or the output side of isolation transformer 34, both current values A1 and A2 increase by the same amount regardless of the increase in potential difference V1, and current value A2 repeatedly increases and decreases due to the AC leakage current. Therefore, even in this case, the value of leakage current can be accurately calculated from the difference Ad between current value A1 and current value A2, improving the accuracy of leakage current detection. Furthermore, if such fluctuations in current values A1 and A2 are observed from the measurement results of leakage current monitoring device 80, it can be assumed that leakage current has occurred in the electrical circuit on the output side of SIV30 or the output side of isolation transformer 34.

Furthermore, the leakage current monitoring device 80 can detect not only leakage current during power supply when current flows from the overhead line 4 to the supply line 18, but also leakage current during regenerative braking when current flows from the supply line 18 to the overhead line 4. Since the direction of current during regenerative braking is simply the opposite of the direction of DC power during power supply, the leakage current monitoring device 80 can detect leakage current during regenerative braking in approximately the same manner as during power supply. Furthermore, based on the direction of the current, it can be analyzed from the detection results of the leakage current monitoring device 80 to determine whether the leakage current occurred during power supply or regenerative braking.

Next, the control of each part of the railway vehicle 10 equipped with the leakage current monitoring device 80 will be described in more detail with reference to Figures 3 to 10. Figure 3 is a block diagram showing the electrical configuration of the railway vehicle 10.

As shown in FIG. 3, the control device 60 of the railway vehicle 10 has a CPU 61, a hard disk drive (HDD) 62, and a RAM 63, which is a memory for rewritably storing various work data, flags, etc. when the CPU 61 executes a program, and these are each connected to an input/output port 65 via a bus line 64.

Further connected to the input/output port 65 are a VVVF inverter 20, an SIV 30, a controller 66, a three-phase AC device 15, a single-phase AC device 16, a DC device 19, a position detection device 67, a speed sensor 68, a temperature sensor 69, a humidity sensor 70, a leakage current monitoring device 80, and a wireless communication device 71 that transmits and receives information to and from an external server 90 via the Internet or the like.

The CPU 61 is a computing device that controls each part connected by the bus line 64. The HDD 62 is a rewritable non-volatile memory that stores the programs executed by the CPU 61 and various data, and is provided with a control program 62a. When the control program 62a is executed by the CPU 61, the main processing of FIG. 4 is executed.

The controller 66 is a device mounted in the cab of the railcar 10 and operated by the driver to control the VVVF inverter 20 and the brakes. The controller 66 switches between powering (P1, P2...) in which the electric motor 22 is driven by controlling the VVVF inverter 20, coasting (N) in which the railcar 10 runs by inertia without driving the electric motor 22, and braking (B1, B2...) to decelerate the railcar.

The position detection device 67 is a device that detects the traveling position of the railway vehicle 10, and in this embodiment, it is composed of a GPS receiver that uses GPS to obtain the current position of the railway vehicle 10. The position detection device 67 is not limited to a GPS receiver, and it is of course possible to adopt other position detection devices. Examples of other position detection devices include an antenna (transponder type) that receives monitor information about the vehicle and signals emitted from the track side, a signal receiver that detects the position using signals from ground coil position information of ground signal devices, and a distance meter that obtains the traveling distance from a base point by integrating the number of rotations of the wheels 13.

The speed sensor 68 is a sensor for detecting the traveling speed of the railcar 10. The position detection device 67 may also function as the speed sensor 68 by calculating the traveling speed of the railcar 10 from the position information of the position detection device 67. The temperature sensor 69 is a sensor for detecting the temperature (air temperature) around the railcar 10. The humidity sensor 70 is a sensor for detecting the humidity around the railcar 10. The temperature sensor 69 and the humidity sensor 70 do not need to be installed on the railcar 10.

Next, referring to FIG. 4, the main processing executed by the CPU 61 of the control device 60 of the railway vehicle 10 will be described. FIG. 4 is a flowchart of the main processing of the control device 60. The main processing of the control device 60 is executed when the pantograph 17 rises, power is supplied to the railway vehicle 10 from the overhead line 4, and the control device 60 is powered on.

As shown in FIG. 4, the main process first acquires various running state data (S11). This running state data includes the operation state of the controller 66, the running position of the railcar 10 detected by the position detection device 67, the running speed of the railcar 10 detected by the speed sensor 68, the temperature detected by the temperature sensor 69, and the humidity detected by the humidity sensor 70. In addition to these data, the running state data may also include the direction of travel of the railcar 10, whether or not three-phase AC equipment 15, single-phase AC equipment 16, DC equipment 19, etc. are in use, information on their use (for example, the set temperature of air conditioning equipment), and the time when each of these data was acquired.

After the process of S11, the acquired driving state data is transmitted to the leakage current monitoring device 80 (S12). This is to transmit data on the current values A1 and A2 measured by the leakage current monitoring device 80 together with the driving state data at the time the current values A1 and A2 were measured to the external server 90. Although not shown, the processes of S11 and S12 are actually controlled to be executed every 20 ms.

After the process of S12, it is confirmed whether the railway vehicle 10 and the external server 90 can communicate with each other via the wireless communication device 71 (S13). If communication with the external server 90 is possible (S13: Yes), a transmission permission signal to the external server 90 is transmitted to the leakage current monitoring device 80 in order to transmit data related to the current values A1 and A2 from the leakage current monitoring device 80 to the external server 90 (S14).

Next, other processes are executed (S15), and the processes from S11 onwards are executed repeatedly. The processes of S15 include various processes for running the railway vehicle 10. Also, in the process of S13, if communication with the external server 90 is not possible (S13: No), the process of S14 is skipped and the process of S15 is executed.

Next, the control in the leakage current monitoring device 80 will be described with reference to FIG. 5. FIG. 5 is a block diagram showing the electrical configuration of the leakage current monitoring device 80. As shown in FIG. 5, the leakage current monitoring device 80 has a CPU 81, a flash ROM 82, and a RAM 83, which are each connected to an input/output port 85 via a bus line 84. The input/output port 85 is further connected to an interface (I/F) 86 connected to the input/output port 65 of the railway vehicle 10, a supply side current transformer 87, a ground side current transformer 88, and a potential difference detection unit 89.

The CPU 81 is a calculation device that controls each part connected by the bus line 84. The flash ROM 82 is a rewritable non-volatile memory that stores programs executed by the CPU 81, fixed value data, etc., and is provided with a monitoring program 82a, a unique number memory 82b, a peak detection memory 82c, a short-term change detection memory 82d, a long-term change detection memory 82e, and a cycle collection memory 82f. When the CPU 81 executes the monitoring program 82a, the main processing of FIG. 7 is executed.

The unique number memory 82b is a memory in which the unique number of the leakage current monitoring device 80 is stored. This unique number is part of the information indicating the measurement target of the current values A1 and A2 by the leakage current monitoring device 80 (the railway vehicle 10 on which the leakage current monitoring device 80 is mounted). The external server 90 is configured to receive data on the current values A1 and A2 and this unique number from the leakage current monitoring device 80, thereby being able to identify the railway vehicle 10 that is the measurement target.

The peak detection memory 82c, the short-term change detection memory 82d, the long-term change detection memory 82e, and the cycle collection memory 82f are all memories for storing data on the current values A1 and A2 measured by the supply side current transformer 87 and the ground side current transformer 88 until they are transmitted to the external server 90. In other words, each of these memories 82c to 82f stores data that is permitted to be transmitted to the external server 90.

RAM 83 is a memory for rewritably storing various work data, flags, etc. when the CPU 81 executes a program, and is provided with a driving state ring buffer 83a, a difference ring buffer 83b, an average value ring buffer 83c, and a potential difference ring buffer 83d.

The contents of the running state ring buffer 83a will be described in detail with reference to FIG. 6(a). The running state ring buffer 83a is a memory that stores the past 10 minutes of running state data acquired by the railway vehicle 10 every 20 ms (received from the control device 60 every 20 ms). For this reason, the running state ring buffer 83a is provided with memories associated with each other by No. 1 to 30,000, and a memory (not shown) that stores the location of the most recent running state data among those memories.

The memories associated with No. 1 to 30000 are memories in which various running state data is stored, and include a control memory in which the operating state of the controller 66 is stored, a position memory in which the running position of the railcar 10 detected by the position detection device 67 is stored, a speed memory in which the running speed of the railcar 10 detected by the speed sensor 68 is stored, a temperature memory in which the temperature detected by the temperature sensor 69 is stored, and a humidity memory in which the humidity detected by the humidity sensor 70 is stored.

The driving state ring buffer 83a stores the latest driving state data in each memory in order from No. 1 to No. 30000, and when the latest driving state data is stored in No. 30000, it is overwritten with the latest driving state data again, starting from No. 1. Since the driving state data is stored in order in this way, the driving state ring buffer 83a is configured to know the time when each driving state data was stored (the time when the driving state data was acquired/received) by using the position where the latest driving state data was stored as the current time. Note that a memory for storing the time when the driving state data was acquired may be provided in the driving state ring buffer 83a.

Returning to FIG. 5, the differential ring buffer 83b is a memory that stores the difference Ad based on the current values A1 and A2 for the past minute. The difference Ad is a value obtained by correcting the difference between the current value A1 measured by the supply-side current transformer 87 and the current value A2 measured by the ground-side current transformer 88 based on the potential difference V1 measured by the potential difference detection unit 89, and is calculated every 1 ms.

The average value ring buffer 83c is a memory that stores the average value of the difference Ad for one minute for the past ten minutes. The average value of the difference Ad for one minute is calculated every minute. The potential difference ring buffer 83d is a memory that stores the potential difference V1 measured every 1 ms by the potential difference detection unit 89 for ten minutes. Each of these ring buffers 83b to 83d is configured in the same way as the driving state ring buffer 83a, except for the content of the data stored and the storage capacity.

Next, the main processing executed by the CPU 81 of the leakage current monitoring device 80 will be described with reference to Figures 7 to 10. Figure 7 is a flowchart of the main processing of the leakage current monitoring device 80. Figure 8 is a flowchart of the peak detection process S28. Figure 9 is a flowchart of the average detection process S29. Figure 10 is a flowchart of the cycle collection process S30.

The main processing of the leakage current monitoring device 80 is executed every 1 ms after the pantograph 17 is raised, power is supplied to the railway vehicle 10 from the overhead line 4, and the leakage current monitoring device 80 is powered on. The peak detection process S28, the average detection process S29, and the cycle collection process S30 are executed during the main processing of the leakage current monitoring device 80.

As shown in FIG. 7, the main process first stores the driving state data transmitted from the control device 60 in the process of S12 in FIG. 4 in the driving state ring buffer 83a (S21) when the leakage current monitoring device 80 receives the driving state data. Note that, although not shown, if the leakage current monitoring device 80 has not received driving state data from the control device 60, the process of S21 is skipped.

After the process of S21, the current value A1 measured by the supply side current transformer 87 is obtained (S22), and the current value A2 measured by the ground side current transformer 88 is obtained (S23). Next, the potential difference V1 measured by the potential difference detection unit 89 is obtained, and the potential difference V1 is stored in the potential difference ring buffer 83d (S24). In this series of processes from S22 to S24, the current value A1, current value A2, and potential difference V1 measured at the same timing are obtained. This is to accurately calculate the leakage current that occurred during the measurement. However, the timings at which the current value A1, current value A2, and potential difference V1 are measured in the processes from S22 to S24 may be different from each other.

After the process of S24, the reference potential difference Vs, which is the reference value of the potential difference V1, is set to 1500 [V] (S25). The reference potential difference Vs may be set according to the electromotive force at the substation 6 that supplies power to the railway vehicle 10 via the overhead line 4. For example, if the electromotive force at the substation 6 is 25,000 V, the reference potential difference Vs is set to 25,000 V in the process of S25.

After the process of S25, the difference Ad = (A1 - A2) · V1/Vs is calculated by correcting the difference between the current value A1 and the current value A2 to the value at the reference potential difference Vs based on these values (S26). Next, the calculated difference Ad is temporarily stored in the latest position of the difference ring buffer 83b (S27). After that, based on the temporarily stored difference Ad, peak detection process S28, average detection process S29, and cycle collection process S30 are executed in order to determine whether data related to the difference Ad should be stored so that it can be transmitted to the external server 90.

The peak detection process S28 in FIG. 8 will be described with reference to FIG. 2(b). The peak detection process S28 is a process for storing the difference Ad (leakage current value) temporarily stored in the difference ring buffer 83b in the peak detection memory 82c for analysis by the external server 90 when the difference Ad (leakage current value) is a value suspected of being abnormal or a value requiring attention or warning.

In the peak detection process S28, first, it is determined whether the difference Ad stored in the latest position of the difference ring buffer 83b has changed from less than the threshold to more than the threshold, i.e., whether the difference Ad at the previous position is less than the threshold and the difference Ad at the latest position is more than the threshold (S41). An example of this threshold is 1 mA. If the difference Ad is more than the threshold, it is suspected that an abnormal leakage current is occurring in the electric circuit monitored by the leakage current monitoring device 80. However, in order to prevent the occurrence of abnormal leakage current, a value smaller than the value that is determined to be abnormal may be set as the threshold. A value greater than 1 mA may also be set as the threshold.

In the process of S41, if the difference Ad of the latest position changes from less than the threshold to equal to or greater than the threshold (S41: Yes), it is checked whether the start position S (see FIG. 2(b)) for specifying the range to be stored in the peak detection memory 82c has not been set (S42). Note that if the difference Ad remains less than the threshold for 15 seconds or more, the start position S is not set (cleared).

If the start position S has not been set (S42: Yes), the start position S is set to the position 15 seconds before the most recent position where the difference Ad became equal to or greater than the threshold value among the multiple memory positions in the difference ring buffer 83b (S43), and the peak detection process S28 is terminated.

In the process of S41, if the difference Ad of the latest position has not changed from less than the threshold to more than the threshold (S41: No), it is determined whether the difference Ad stored in the latest position of the difference ring buffer 83b has changed from more than the threshold to less than the threshold (S45). If the difference Ad has changed from more than the threshold to less than the threshold (S45: Yes), since the start position S has already been set in the process of S43, the end position E (see FIG. 2(b)) corresponding to the start position S is set (S46), and the peak detection process S28 is terminated.

Specifically, in the process of S46, of the multiple memory positions in the difference ring buffer 83b, the position 15 seconds after the most recent position where the difference Ad became less than the threshold is set as the end position E. The range of the difference ring buffer 83b from the start position S to the end position E is the range to be stored in the peak detection memory 82c.

If the difference Ad of the latest position does not cross the threshold (S41: No and S45: No), it is checked whether a new difference Ad has been stored in the end position E of the difference ring buffer 83b (S47). That is, in the process of S47, it is checked whether 15 seconds have passed since the difference Ad fell below the threshold while remaining below the threshold.

If a new difference Ad is stored at the end position E in the process of S47 (S47: Yes), all the differences Ad in the range to be stored in the peak detection memory 82c are now stored in the peak detection memory 82c (S48). Furthermore, in the process of S48, the driving state data and the potential difference V1 at the time corresponding to these differences Ad are stored in the peak detection memory 82c in association with the differences Ad.

Specifically, as shown in FIG. 6(b), the peak detection memory 82c includes a time memory in which the time is stored, a difference memory in which the difference Ad is stored, a control memory, a position memory, a speed memory, a temperature memory, a humidity memory, and a potential difference memory in which the potential difference V1 is stored. Note that the control memory to the humidity memory are the same as those described above for the driving state ring buffer 83a in FIG. 6(a).

The time stored in the time memory is the time when the difference Ad was calculated (the time when the current values A1 and A2 were obtained), the time when the driving state data such as the operation state of the controller was obtained, and the time when the potential difference V1 was obtained. That is, each of these values is associated with each other by time and stored in the peak detection memory 82c.

This makes it possible to analyze the cause of a difference Ad (leakage current value) that is large enough to suspect an abnormality from the driving state data. For example, if the difference Ad exceeds the threshold only when the brakes are applied, it can be assumed that there is an abnormality in the electrical circuit related to the brakes.

Returning to FIG. 8, the explanation will be given below. After the process of S48, the settings of the start position S and the end position E are cleared (S49) so that a new start position S can be set in the processes of S41 to S43, and the peak detection process S28 is terminated.

Here, we will explain the case where the start position S is set in the process of S43, the difference Ad becomes less than the threshold value (S45: Yes), the end position E is set in the process of S46, and then the difference Ad of the latest position becomes equal to or greater than the threshold value (S41: Yes) before the difference Ad is stored in the end position E.

In this case, since both the start position S and the end position E have already been set in the process of S42 (S42: No), the start position S is not reset in the process of S43, and only the end position E is cleared so that it can be reset (S44, see the dashed line in FIG. 2(b)), and the peak detection process S28 ends. After that, if the latest difference Ad again goes from being equal to or greater than the threshold to being less than the threshold (S45: No), the end position E is reset (S46), and the difference Ad from the start position S to the end position E can be stored in the peak detection memory 82c by the processes of S47 and S48.

In this way, even if there are successive portions in which the difference Ad is equal to or greater than the threshold value over a short period of time, the difference Ad for multiple consecutive ranges that are equal to or greater than the threshold value and the difference Ad for 15 seconds before and after the ranges can be stored in the peak detection memory 82c. In other words, it is possible to avoid a situation in which some of the multiple ranges in which the difference Ad is equal to or greater than the threshold value are not stored in the peak detection memory 82c. Furthermore, compared to a case in which the start position S and end position E are set individually for multiple ranges in which the difference Ad is equal to or greater than the threshold value, the peak detection process S28 can be simplified and duplicate data can be prevented from being stored in the peak detection memory 82c.

If no new difference Ad is stored at the end position E in the process of S47 (S47: No), it is confirmed whether the position at which the difference Ad is to be stored next in the difference ring buffer 83b is the start position S (S50). If the position to be stored next is not the start position S (S50: No), the peak detection process S28 is terminated.

On the other hand, if the next position to be stored is the start position S (S50: Yes), the storage of new differences Ad in the difference ring buffer 83b from the next time onwards will cause the differences Ad to be stored in the peak detection memory 82c to be erased, starting with the oldest. Therefore, just before the old differences Ad are erased (S50: Yes), all differences Ad stored in the difference ring buffer 83b and the driving state data and potential difference V1 at the times corresponding to those differences Ad are associated with each other and stored in the peak detection memory 82c (S51).

If a new difference Ad is stored at the end position E in the peak detection process S28 after the process of S51 (S47: Yes), the process of S48 uses the difference Ad stored in the difference ring buffer 83b immediately after the process of S51 as the new start position S, and stores the difference Ad after the process of S51 in the peak detection memory 82c. Therefore, by the processes of S50 and S51, it is possible to store all of the difference Ad that is equal to or greater than the threshold value and the difference Ad for 15 seconds before and after it in the peak detection memory 82c without increasing the capacity of the difference ring buffer 83b.

Next, the average detection process S29 will be described with reference to FIG. 9. The average detection process S29 is a process for storing the average value of the difference Ad over one minute in the short-term change detection memory 82d or the long-term change detection memory 82e in order to analyze the short-term or long-term increase trend of the difference Ad by the external server 90 while eliminating the influence of the difference Ad that momentarily increases due to noise, etc.

As shown in FIG. 9, in the average detection process S29, first, it is confirmed whether one minute has passed since the previous calculation of the average value, i.e., whether all values in the difference ring buffer 83b that stores the difference Ad for the past one minute have been updated (S61). Note that immediately after the power supply to the leakage current monitoring device 80 is turned on, invalid values are stored in each memory of the difference ring buffer 83b, and in the process of S61 immediately after turning on, it is confirmed whether all invalid values have been updated with the difference Ad. If in the process of S61, one minute has not passed since the previous calculation of the average value or since the power supply was turned on (S61: No), the average detection process S29 is terminated and one minute is awaited.

On the other hand, if one minute has passed since the previous calculation of the average value or the power was turned on (S61: Yes), all values in the difference ring buffer 83b have been updated, so the differences Ad for the most recent minute stored in the difference ring buffer 83b are averaged to calculate an average value, and this average value is stored in the average value ring buffer 83c (S62).

Next, the rate of change of the average value for the most recent minute relative to the average value from 2 to 1 minute ago stored in the average value ring buffer 83c (the average value calculated in the process of S62 1 minute ago, which is the average of the multiple differences Ad calculated from 2 to 1 minute ago) is calculated as the short-term change rate (S63). Specifically, it is calculated as (short-term change rate) = ((average value for the most recent minute) - (average value from 2 to 1 minute ago)) / (average value from 2 to 1 minute ago).

It is then confirmed whether the calculated short-term change rate is equal to or greater than the change threshold (S64). Note that the change threshold is set to, for example, 1.1 to eliminate noise, but may be changed as long as it is a number equal to or greater than 1.

If the short-term change rate is equal to or greater than the change threshold in the process of S64 (S64: Yes), the average values for the most recent two minutes stored in the average value ring buffer 83c (all average values calculated in the process of S62 for the most recent two minutes) are associated with the driving condition data and potential difference V1 at the time corresponding to these average values and stored in the short-term change detection memory 82d (S65), and the process proceeds to S66.

The driving condition data at the time corresponding to the average value for the most recent two minutes is the driving condition data for the most recent two minutes stored in the driving condition ring buffer 83a. The potential difference V1 at the time corresponding to the average value for the most recent two minutes is the potential difference V1 for the most recent two minutes stored in the potential difference ring buffer 83d. As shown in FIG. 6(c), the short-term change detection memory 82d is obtained by replacing the difference memory of the peak detection memory 82c in FIG. 6(b) with an average value memory in which the average value of the difference Ad is stored. The average value is stored in the average value memory so as to correspond to the time when the oldest difference Ad used to calculate the average value was calculated.

If the short-term change rate is less than the change threshold in the process of S64 (S64: No), the process of S65 is skipped and the process proceeds to S66. This makes it possible to analyze the increasing trend of the short-term average value while eliminating cases where the short-term change rate is decreasing or where the short-term change rate is only slightly increased due to noise, etc.

In the process of S66, the rate of change of the average value for the most recent minute relative to the average value from 10 to 9 minutes ago stored in the average value ring buffer 83c (the average value calculated in the process of S62 9 minutes ago, which is the average of the multiple differences Ad calculated from 10 to 9 minutes ago) is calculated as the long-term rate of change (S66). Specifically, it is calculated as (long-term rate of change) = ((average value for the most recent minute) - (average value from 10 to 9 minutes ago)) / (average value from 10 to 9 minutes ago).

It is then confirmed whether the calculated long-term change rate is equal to or greater than the change threshold (S67). If the long-term change rate is equal to or greater than the change threshold (S67: Yes), the average values for the most recent 10 minutes stored in the average value ring buffer 83c (all average values calculated in the process of S62 for the most recent 10 minutes) are associated with the driving condition data and potential difference V1 at the time corresponding to these average values and stored in the long-term change detection memory 82e (S68), and the average detection process S29 is terminated.

The driving condition data at the time corresponding to the average value for the last 10 minutes is the driving condition data for the last 10 minutes stored in the driving condition ring buffer 83a. The potential difference V1 at the time corresponding to the average value for the last 10 minutes is the potential difference V1 for the last 10 minutes stored in the potential difference ring buffer 83d. In addition, the long-term change detection memory 82e is configured in the same way as the short-term change detection memory 82d.

If the long-term rate of change is less than the change threshold in the process of S67 (S67: No), the process of S68 is skipped and the average detection process S29 is terminated. This makes it possible to analyze the long-term increasing trend of the average value while eliminating cases where the long-term rate of change is decreasing or where the long-term rate of change is only slightly increased due to noise, etc.

Next, the cycle collection process S30 will be described with reference to FIG. 10. The cycle collection process S30 is a process for periodically storing the difference Ad in the cycle collection memory 82f even if there is no abnormality, in order to analyze fluctuations in the difference Ad over an extremely long period, such as several months or years.

As shown in FIG. 10, in the cycle collection process S30, first, it is confirmed whether the regular collection timing has arrived (S71). In this embodiment, the regular collection timing is set to every hour, but the collection timing may be changed as appropriate.

If the regular collection timing has not arrived (S71: No), the cycle collection process S30 is terminated and the arrival of the collection timing is awaited. On the other hand, if the regular collection timing has arrived (S71: Yes), all the differences Ad (for the last minute) stored in the difference ring buffer 83b and the driving state data and potential difference V1 at the time corresponding to those differences Ad are associated with each other and stored in the cycle collection memory 82f (S72), and the cycle collection process S30 is terminated.

In the process of S72, the driving state data at the time corresponding to the difference Ad is the driving state data for the most recent minute stored in the driving state ring buffer 83a. Similarly, the potential difference V1 at the time corresponding to the difference Ad is the potential difference V1 for the most recent minute stored in the potential difference ring buffer 83d.

By periodically acquiring the difference Ad, it is possible to analyze the very long-term increase trend of the leakage current over several months or years. For example, the change over time of the actual measured value of the difference Ad in the past can be approximated using the least squares method, and the change over time of the predicted value of the difference Ad in the future can be calculated. From the change over time of this predicted value, it is possible to analyze the approximate date and time when the difference Ad will exceed a threshold value (e.g., 1 mA). This makes it possible to plan schedules for maintenance of the railway vehicle 10, as well as to plan the ordering of equipment and parts that require replacement.

Returning to FIG. 7, the explanation is given below. After the cycle collection process S30, it is confirmed whether a transmission permission signal has been received from the control device 60 (S31). If the leakage current monitoring device 80 receives the transmission permission signal transmitted by the control device 60 in the process of S14 in FIG. 4 (S31: Yes), communication between the railcar 10 (leakage current monitoring device 80) and the external server 90 is possible via the wireless communication device 71, so the untransmitted data stored in the peak detection memory 82c, short-term change detection memory 82d, long-term change detection memory 82e, and cycle collection memory 82f, as well as the unique number stored in the unique number memory 82b, are transmitted to the external server 90 (S32).

The data stored in each of these memories 82c to 82f includes the difference Ad itself based on the current values A1 and A2, and includes the average value of the difference Ad, and is permitted to be transmitted to the external server 90. Therefore, the processes of S41 to S47, S50 in FIG. 8, S63, S64, S66, S67 in FIG. 9, and S71 in FIG. 10, which determine whether to store each data in each of the memories 82c to 82f, can be said to be processes that determine whether to transmit each data to the external server 90. In particular, the processes of S41 to S47, S50 in FIG. 8, and S63, S64, S66, S67 in FIG. 9 can be said to be processes that determine whether to transmit data related to the difference Ad to the external server 90 based on the difference Ad itself or the average value of the difference Ad. In addition, the processes of S48 and S51 in FIG. 8, S65 and S68 in FIG. 9, and S72 in FIG. 10 can be said to be processes that enable each data item determined to be sent to the external server 90 to be sent to the external server 90.

As a result, for example, data effective for analyzing leakage current can be selected from the data related to the difference Ad and transmitted to the external server 90, thereby reducing the frequency and amount of transmission from the railway vehicle 10 to the external server 90. Furthermore, when data is temporarily stored before transmission to the external server 90, the amount of data can be reduced, making it easier to miniaturize and reduce costs for the leakage current monitoring device 80.

After the process of S32, other processes are executed (S33), and the main process of the leakage current monitoring device 80 is terminated. Also, if the transmission permission signal is not received from the control device 60 in the process of S31 (S31: No), the process of S32 is skipped, the process of S33 is executed, and the main process of the leakage current monitoring device 80 is terminated. The process of S33 may include a process of changing the reference potential difference Vs, a process of changing the threshold value used in the peak detection process S28, and a process based on a signal received from the external server 90. For example, if the external server 90 performs an operation to change the threshold value used in the peak detection process S28 and the leakage current monitoring device 80 receives the change signal from the external server 90 via the wireless communication device 71, the process of S33 executes a process of changing the threshold value according to the received signal.

Next, the processing in the external server 90 will be described. When the external server 90 receives the data and unique number of each memory 82c to 82f transmitted from the leakage current monitoring device 80 in the processing of S32, it stores each data in each memory provided in the external server 90 for each unique number (railroad vehicle 10 to be measured). Note that each memory of the external server 90 is substantially the same as each memory 82c to 82f of the leakage current monitoring device 80.

The external server 90 performs an analysis of the cause of leakage current generation, etc., using each piece of data received from the leakage current monitoring device 80. For this analysis, it is preferable to use AI-based data analysis. Specifically, the analysis in the external server 90 will be explained using an example in which the contents of the peak detection memory 82c shown in FIG. 6(b) and the contents of the short-term change detection memory 82d shown in FIG. 6(c) are stored in the external server 90.

As shown in FIG. 6(b), when the difference memory value (leakage current value) increases from 0.5 mA to 1.2 mA, which is above the threshold, the operation state of the controller 66, which is the value of the control memory, changes from "N" to "B1", and the position of the railway vehicle 10, which is the value of the position memory, changes from "X1, Y1" to "X2, Y2". Therefore, the external server 90 can infer that the increase in the leakage current value is caused by the controller 66 being at "B1" or the position of the railway vehicle 10 being at "X2, Y2".

Furthermore, assume that thereafter, when the position of the railway vehicle 10 hardly moves from "X2, Y2" and the state of the controller 66 changes from "B1" to another state such as "N", the value of the leakage current falls below the threshold value. In this case, the external server 90 can infer that the increase in the value of the leakage current is caused by an electric circuit that is energized only when the controller 66 is "B1".

On the other hand, if the state of the controller 66 remains at "B1" and the position of the railway vehicle 10 moves significantly from "X2, Y2", and the leakage current value falls below the threshold value, it can be presumed that the increase in the leakage current value is caused by the position of the railway vehicle 10. For example, if there is ground equipment such as snow melting removal equipment at the position of "X2, Y2", it can be presumed that the ground equipment is the cause of the increase in the leakage current value.

Also, as shown in FIG. 6(c), the one-minute average value of the difference Ad increases only when the state of the controller 66 is "P2" compared to the previous states of "N" and "B1". From this, it can be inferred that in the external server 90, the leakage current of the electric circuit that is energized only when the controller 66 is "P2" is on the rise, and that the insulation resistance of the circuit is deteriorating.

The cause of the increase in the leakage current value is not limited to the operation state of the controller 66 or the position of the railway vehicle 10, but can also be estimated from other running state data and the potential difference V1. For example, the control state of the VVVF inverter 20 can be identified from the running speed of the railway vehicle 10, which is the value of the speed memory, and the operation state of the controller 66. As a result, if the leakage current increases in a specific control state of the VVVF inverter 20, it can be estimated that the increase in the leakage current value is caused by an electric circuit that is energized only in that specific control state.

In addition, the insulation resistance value of each part of the railway vehicle 10 varies with temperature and humidity. Therefore, the value of the leakage current, which depends on the insulation resistance value, also varies with temperature and humidity. Therefore, from the temperature around the railway vehicle 10, which is the value of the temperature memory, it can be estimated whether the variation in the value of the leakage current is dependent on temperature or on other changes. Similarly, from the humidity around the railway vehicle 10, which is the value of the humidity memory, it can be estimated whether the variation in the value of the leakage current is dependent on humidity or on other changes.

As described above, the leakage current monitoring device 80 transmits data on the difference Ad (leakage current value) and the average value of the difference Ad to the external server 90 in association with the driving condition data and the potential difference V1, making it easier to analyze the cause of leakage current generation. Furthermore, compared to when the leakage current analysis is performed by the leakage current monitoring device 80, the leakage current monitoring device 80 can be made smaller and less expensive.

Next, the second embodiment will be described with reference to FIG. 11. In the first embodiment, a case where a leakage current monitoring device 80 is installed in a railway vehicle 10 consisting of one car is described. In contrast, in the second embodiment, a case where a leakage current monitoring device 110 is provided in a train consisting of railway vehicles 100a, 100b, and 100c coupled together is described. Note that the same parts as in the first embodiment are given the same reference numerals and the following description is omitted.

Figure 11 is a circuit diagram that shows a schematic of the electric circuit of the railway cars 100a, 100b, and 100c in the second embodiment. In Figure 11, the electric motor wire 24 and the first low-voltage AC circuit 32 are shown as single-line diagrams, and the two electric wires 36r and 36t of the second low-voltage AC circuit 36 are shown as one wire.

Each of the railway cars 100a to 100c mainly comprises a car body 12, wheels 13, and coupling parts 14. The railway cars 100a to 100c are configured into a train set by coupling the coupling parts 14 together. The grounding wires 41 provided on each of the railway cars 100a to 100c are connected to each other via the coupling parts 14.

All of the railway cars 100a to 100c are equipped with a supply train line 18a (part of the supply line) that is routed between the coupling parts 14 at both ends of the car body 12 and connected to each other. Each of the railway cars 100a and 100c is equipped with a pantograph 17, and is provided with an upstream supply line 18b (part of the supply line) that connects the pantograph 17 to the supply train line 18a. The railway car 100b is not equipped with a pantograph 17, and runs on power supplied from the railway cars 100a and 100c.

The railway vehicle 100c is a powered vehicle capable of self-propelling on rails 2, and is equipped with a VVVF inverter 20 to which power is supplied from a supply lead-in line 18a, and an electric motor 22 connected to the output side of the VVVF inverter 20 via an electric motor wire 24. An electric wire branching off from the supply lead-in line 18a is connected to the positive terminal on the input side of the VVVF inverter 20, and a ground side electric wire 45 branching off from the ground lead-in line 41 is connected to the negative terminal of the VVVF inverter 20.

Railroad cars 100a and 100b are trailer cars that do not have electric motors 22 and run alongside railroad car 100c. It is also possible to mount electric motors 22 on railroad cars 100a and 100b and connect the electric motors 22 to the VVVF inverter 20 of railroad car 100c with electric motor wires 24.

The railway vehicle 100b includes an SIV 30 to which power is supplied from a supply lead-in line 18a, a first low-voltage AC circuit 32 connected to the output side of the SIV 30, an isolation transformer 34 whose primary winding is connected to the first low-voltage AC circuit 32, and a second low-voltage AC circuit 36 connected to the secondary winding of the isolation transformer 34. An electric wire branched off from the supply lead-in line 18a is connected to the positive terminal on the input side of the SIV 30, and a ground side electric wire 45 branched off from a ground lead-in line 41 is connected to the negative terminal of the SIV 30.

Railway vehicles 100a and 100c are each provided with a first low-voltage AC circuit 32 connected to the first low-voltage AC circuit 32 of railway vehicle 100b via a coupling portion 14, and a second low-voltage AC circuit 36 connected to the second low-voltage AC circuit 36 of railway vehicle 100b via a coupling portion 14. A plurality of three-phase AC devices 15 are connected to the first low-voltage AC circuit 32 of railway vehicles 100a to 100c, and single-phase AC devices 16 and DC devices 19 are connected to the second low-voltage AC circuit 36.

A train consisting of such railway cars 100a to 100c is equipped with a leakage current monitoring device 110 that monitors leakage currents occurring in the electric circuits. In this embodiment, the main body of the leakage current monitoring device 110 (CPU 71, etc.) is mounted on the railway car 100a. The main body of the leakage current monitoring device 110 may be mounted on railway cars 100b and 100c, or the main body of the leakage current monitoring device 110 may be mounted on each of the railway cars 100a to 100c, and these main bodies may be configured to be able to communicate with each other.

The leakage current monitoring device 110 includes supply side current transformers (supply side measuring instruments) 87a, 87c through which the upstream supply lines 18b of the railcars 100a, 100c are passed, ground side current transformers (ground side measuring instruments) 88a, 88b, 88c through which the aggregated lines 42 of the railcars 100a, 100b, 100c are passed, and a potential difference detector 89 that measures the potential difference between the upstream supply line 18b of the railcar 100a and the aggregated line 42. The leakage current monitoring device 110 is configured substantially the same as the leakage current monitoring device 80 in the first embodiment, except that the number of supply side current transformers 87a, 87c and ground side current transformers 88a to 88c has been increased.

The supply side current transformers 87a and 87c measure the current value of the supply upstream line 18b through which the supply upstream line 18b passes. As a result, even if, for example, a current from the pantograph 17 of the railcar 100a and a current from the pantograph 17 of the railcar 100c each flow through the supply line 18a of the railcar 100b, the supply side current transformers 87a and 87c can accurately detect the current value of the power supplied from the pantograph 17 to each of the railcars 100a and 100c.

In a train consisting of railway cars 100a to 100c, the current from the pantographs 17 of railway cars 100a and 100c passing through the supply side current transformers 87a and 87c is divided into a current passing through the collective line 42 (ground side current transformer 88a) of railway car 100a, a current passing through the collective line 42 (ground side current transformer 88b) of railway car 100b, a current passing through the collective line 42 (ground side current transformer 88c) of railway car 100c, and a leakage current that occurs in railway cars 100a to 100c and bypasses the collective line 42.

Of these currents, the leakage current monitoring device 110 can measure the current from the pantograph 17 of the railway cars 100a, 100c using the supply side current transformers 87a, 87c, and can measure the current passing through the aggregated wire 42 of the railway cars 100a-100c using the ground side current transformers 88a-88c. Therefore, from these current values, the leakage current bypassing the aggregated wire 42 can be calculated with high accuracy, and the detection accuracy of the leakage current can be improved as in the first embodiment.

Specifically, in the leakage current monitoring device 110, the current value A1 used to calculate the difference Ad (leakage current value) is the sum of the current value of the supply side current transformer 87a and the current value of the supply side current transformer 87c. In addition, the current value A2 used to calculate the difference Ad is the sum of the current values of the ground side current transformers 88a to 88c.

Furthermore, the leakage current monitoring device 110 may transmit not only the difference Ad but also the current values of each of the supply side current transformers 87a, 87c and each of the ground side current transformers 88a to 88c to the external server 90. This may enable an analysis to determine in which of the railway cars 100a to 100c a leakage current is occurring, based on each current value.

In addition, in a train consisting of railway cars 100a to 100c, for example, current flowing from the grounding lead-in wire 41 of railway car 100a to the grounding lead-in wire 41 of railway car 100b may pass through the aggregated wire 42, the wheels 13, and the rails 2 without passing through the coupling part 14. This type of current is called a stray current due to circulation. Since this stray current due to circulation passes through the aggregated wire 42, the occurrence of the stray current can be analyzed from the current values of the ground side current transformers 88a to 88c. Similarly, if a stray current other than a circulating current passes through the aggregated wire 42, the occurrence of the stray current can be analyzed from the current values of the ground side current transformers 88a to 88c.

Next, a third embodiment will be described with reference to FIG. 12. In the first and second embodiments, the leakage current monitoring device 80, 110 is mounted on the railway cars 10, 100a to 100c, which are DC electric trains. In contrast, in the third embodiment, the leakage current monitoring device 80 is mounted on the railway car 150, which is an AC electric train. Note that the same parts as in the first and second embodiments are given the same reference numerals and the following description will be omitted.

Figure 12 is a circuit diagram that shows a schematic of the electrical circuit of a railway vehicle 150 in the third embodiment. The railway vehicle 150 is an AC electric train, and mainly includes a car body 12, wheels 13, and a coupling portion 14.

A high-voltage (25,000 V in this embodiment) single-phase AC current flows through the overhead wire 140 that is suspended above the rail 2 by generating an electromotive force at the substation 141 with respect to the grounded rail 2. By raising the pantograph 17 to contact the overhead wire 140, AC power for running the vehicle is supplied from the overhead wire 140 via the pantograph 17 to the supply upstream line 18b and supply lead line 18a of the railway vehicle 150.

The electric wire branching off from the supply lead wire 18a and the ground side electric wire 45 branching off from the ground lead wire 41 are connected by the primary winding of the main transformer 151. The main transformer 151 is an insulating transformer that transforms and outputs the input voltage and insulates the input side from the output side, and has a secondary winding and a tertiary winding on the output side relative to the primary winding on the input side.

An AC/DC converter 152 that converts the AC power output from the main transformer 151 into DC power is connected to the secondary winding of the main transformer 151. The output side of this AC/DC converter 152 is connected to the VVVF inverter 20. AC power is supplied from the VVVF inverter 20 to the motor 22 via the motor wire 24.

A first low-voltage AC circuit 32 is connected to the tertiary winding of the main transformer 151. A primary winding of an isolation transformer 34 is connected to the first low-voltage AC circuit 32, and a second low-voltage AC circuit 36 is connected to the secondary winding of the isolation transformer 34. The first low-voltage AC circuit 32 in this third embodiment is configured in the same way as the three-phase first low-voltage AC circuit 32 in the first and second embodiments, except that it is single-phase, so the same reference numerals are used and a description is omitted. A single-phase AC device 15a such as an air conditioner that operates on 440V single-phase AC is provided on the first low-voltage AC circuit 32.

Similarly, the second low-voltage AC circuit 36 in the third embodiment is configured in the same way as the second low-voltage AC circuit 36 in the first and second embodiments except for the number of electric wires, so the same reference numerals are used and the description is omitted. The second low-voltage AC circuit 36 is provided with a plurality of single-phase AC devices 16 that operate on 100V single-phase AC, and a plurality of DC devices 19 via a rectifier (not shown).

In addition, the isolation transformer 34 in the third embodiment converts the 440V single-phase AC input from the first low-voltage AC circuit 32 into a 100V single-phase AC and outputs it to the second low-voltage AC circuit 36. Note that the isolation transformer 34 may be omitted, and a quaternary winding connected to the second low-voltage AC circuit 36 may be provided in the main transformer 151, and the 100V single-phase AC transformed by the main transformer 151 may be output to the second low-voltage AC circuit 36.

Such a railway vehicle 150 is equipped with a leakage current monitoring device 80 that monitors leakage current occurring in the electric circuit. The supply side current transformer 87 of the leakage current monitoring device 80 has the supply upstream line 18b passing through it and measures the current value of the supply upstream line 18b. The ground side current transformer 88 of the leakage current monitoring device 80 has the aggregated line 42 passing through it and measures the current value of the aggregated line 42. The supply side current transformer 87 and the ground side current transformer 88 in the third embodiment are configured to be able to measure AC current values, but since their configurations are known, their explanations will be omitted. In addition, the potential difference detection unit 89 of the leakage current monitoring device 80 measures the potential difference between the supply upstream line 18b and the aggregated line 42.

In the railway vehicle 150, for example, when leakage current occurs from the supply line 18a to the car body 12 but no other leakage current occurs, the leakage current flows through the car body 12, the ground terminal section 43, and the rail 2, bypassing the aggregated line 42 (ground side current transformer 88). The route of this leakage current is substantially the same as in the first embodiment, except for the direction.

In addition, if a leakage current occurs between the vehicle body 12 and the electrical circuit on the output side of the main transformer 151 or the output side of the isolation transformer 34, the leakage current flows through a route similar to that of the first embodiment. Specifically, the leakage current passes through the vehicle body 12, the ground terminal portion 43, and the aggregated wire 42 so as to return to the main transformer 151 or the isolation transformer 34.

Therefore, the leakage current monitoring device 80 can improve the detection accuracy of the leakage current as in the first embodiment by measuring the current value A1 of the supply side current transformer 87 and the current value A2 of the ground side current transformer 88. Furthermore, as in the first embodiment, the part where the leakage current occurs can be estimated from the way in which the current values A1 and A2 fluctuate.

The leakage current generated in the electrical circuit of the railway vehicle 150, which is an AC electric train, includes leakage current Igc caused by capacitance to the ground, and leakage current Igr caused by insulation resistance to the ground, which is directly related to insulation resistance. The leakage current Igc not only increases in capacity according to the length of the electric wire being measured, but also increases in capacity due to harmonic distortion currents caused by inverters, noise filters, etc. used in electrical equipment.

By detecting the voltage cross point with the potential difference detection unit 89, the leakage current Igr can be calculated from the detection result and the difference between the current values A1 and A2. Note that the leakage current Igr can be calculated using a known method, such as the method disclosed in Japanese Patent No. 4945727.

Therefore, in the main process of FIG. 7 of the leakage current monitoring device 80 in the third embodiment, instead of the processes of S24 to S26, a process is executed to calculate the leakage current Igr as the corrected difference Ad.

Next, the fourth embodiment will be described with reference to FIG. 13. In the first to third embodiments, the case where power is supplied to the railway cars 10, 100a to 100c, 150 from the overhead line 4, 140 via the pantograph 17 has been described. In contrast, in the fourth embodiment, a railway car 160 equipped with a generator 161 instead of the pantograph 17 will be described. Note that the same parts as in the first to third embodiments are given the same reference numerals and the following description will be omitted.

Figure 13 is a circuit diagram showing a schematic diagram of an electrical circuit of a railway vehicle 160 in the fourth embodiment. The railway vehicle 160 mainly comprises a car body 12, wheels 13, a coupling portion 14 (not shown), a VVVF inverter 20, an SIV 30, a grounding wire 40, a generator 161 and a storage battery 165 that generate power for running the vehicle, and an adjustment device 166 that adjusts and outputs the power from the generator 161 and the storage battery 165.

The generator 161 is a three-phase, four-wire generator that generates three-phase AC power. A set of three supply lines 162, 163, and 164 that supply three-phase AC power is connected to the generator 161. In addition, the neutral line 161a extending from the neutral point of the generator 161 is connected to the grounding line 41 of the grounding line 40 via the manual switch 46f. As a result, when the manual switch 46f is closed, the neutral point of the generator 161 is grounded.

The storage battery 165 is a battery that charges and discharges DC power. A positive electrode wire 165a is connected to the positive electrode of the storage battery 165, and a negative electrode wire 165b is connected to the negative electrode of the storage battery 165. The current generated by the storage battery 165 is supplied to each part from the positive electrode wire 165a and returns from the negative electrode wire 165b.

The adjustment device 166 is connected to the supply lines 162, 163, and 164, and is a device that converts the three-phase AC power from the generator 161 into DC power and outputs it. Furthermore, the adjustment device 166 is connected to the positive pole line 165a and the negative pole line 165b, and outputs the DC power from the storage battery 165 together with the DC power obtained by converting the AC power from the generator 161. For example, when the power to be output is insufficient simply by converting the AC power from the generator 161, the adjustment device 166 controls the supply of DC power from the storage battery 165 to make up for the shortage.

The adjustment device 166, the generator 161, and the storage battery 165 may be collectively regarded as a single on-board power source mounted on the railway vehicle 160. Also, each of the generator 161 or the storage battery 165 may be regarded as an on-board power source mounted on the railway vehicle 160.

The output side of the adjustment device 166 is connected to a supply line 18 for supplying DC power to the VVVF inverter 20 and the SIV 30, and a ground side electric wire 45 to which DC power returns from the VVVF inverter 20 and the SIV 30. The supply line 18 is connected to the positive terminal of the input side of the VVVF inverter 20 and the SIV 30, and the ground side electric wire 45 is connected to the negative terminal of the input side of the VVVF inverter 20 and the SIV 30. A branch line 45a branching from the ground side electric wire 45 is connected to the ground lead line 41 via a manual switch 46g. As a result, when the manual switch 46g is closed, the ground side electric wire 45 is grounded and forms part of the ground line 40.

Such a railway vehicle 160 is equipped with a leakage current monitoring device 170 that monitors the leakage current occurring between the generator 161 and the regulating device 166, and a leakage current monitoring device 180 that monitors the leakage current occurring downstream of the regulating device 166.

The leakage current monitoring device 170 includes three supply side current transformers 171, 172, 173 through which the three supply lines 162, 163, 164 pass, and which measure the current values of the supply lines 162, 163, 164 individually. Each of the supply side current transformers (supply side measuring instruments) 171 to 173 is a measuring instrument composed of a ring-shaped current transformer through which the electric wire to be measured passes, and measures the current value flowing through the passed part. If no leakage current is occurring between the generator 161 and the adjustment device 166, the sum (difference) of the current values of the three supply side current transformers 171 to 173 is basically 0 [A].

On the other hand, if leakage current to the vehicle body 12 occurs downstream of the supply side current transformers 171-173 between the generator 161 and the adjustment device 166, the leakage current flows through the vehicle body 12, the ground wire 40, and the neutral wire 161a. Therefore, the sum of the current values of the supply side current transformers 171-173 can be accurately calculated as the value of the leakage current. Therefore, by monitoring the current values of the supply side current transformers 171-173, the leakage current monitoring device 170 can improve the detection accuracy of the leakage current occurring between the generator 161 and the adjustment device 166.

It is possible to measure the total current value flowing through the supply lines 162-164 by passing the three supply lines 162-164 through one current transformer. However, if the supply lines 162-164 are separated from each other, it is necessary to use a large-diameter current transformer or a freely deformable current transformer, which reduces the flexibility of the current transformer that can be used. Furthermore, with a large-diameter current transformer or a freely deformable current transformer, the accuracy of detecting the current value decreases.

In contrast, in this embodiment, the three supply lines 162-164 are passed through the supply side current transformers 171-173 individually, so even if the supply lines 162-164 are separated from each other, the degree of freedom of the supply side current transformers 171-173 can be prevented from decreasing. Furthermore, since the supply side current transformers 171-173 can be easily made small in diameter and have a fixed shape, the detection accuracy of the current value can be improved.

The leakage current flowing through the neutral conductor 161a can also be detected by measuring the current value of the neutral conductor 161a with a current transformer. However, in addition to the leakage current, currents may also be generated in the neutral conductor 161a from various parts of the electrical circuit of the railway vehicle 160 via the ground wire 40, and this may reduce the accuracy of detecting the leakage current occurring between the generator 161 and the adjustment device 166.

In contrast, in this embodiment, the leakage current value is calculated by the sum of the current values of the three supply lines 162 to 164, rather than the current value of the neutral line 161a, thereby improving the detection accuracy of the leakage current occurring between the generator 161 and the adjustment device 166.

The specific control method of the leakage current monitoring device 170 is substantially the same as that of the leakage current monitoring device 80 of the first embodiment, except that the potential difference V1 is not acquired, and the sum of the current values of the supply side current transformers 171 to 173 is taken as the difference Ad (the value of the leakage current).

The leakage current monitoring device 180 includes a supply side current transformer 181 through which the supply line 18 passes, a ground side current transformer 182 through which the ground side electric wire 45 passes, and a battery current transformer 183 through which the positive electrode wire 165a passes. The supply side current transformer (supply side measuring instrument) 181, the ground side current transformer (supply side measuring instrument) 182, and the battery current transformer 183 are all measuring instruments composed of annular current transformers through which the electric wire to be measured passes, and measure the current value flowing through the passed part. The supply side current transformer 181 passes through the portion of the supply line 18 before it branches to the VVVF inverter 20 side and the SIV 30 side, and measures the current value A1 of that portion.

The ground side current transformer 182 is the portion of the ground side electric wire 45 before it branches into the VVVF inverter 20 side and the SIV 30 side, through which the VVVF inverter 20 and SIV 30 side portions pass when branching into the branch line 45a, and measures the current value A2 at that portion.

If no leakage current occurs downstream of the adjustment device 166, current flows from the adjustment device 166 to the VVVF inverter 20 and SIV 30 via the supply line 18, and current returns from the VVVF inverter 20 and SIV 30 to the adjustment device 166 via the ground side electric wire 45. Therefore, in this case, the difference Ad between the current value A1 of the supply side current transformer 181 and the current value A2 of the ground side current transformer 182 is basically 0 [A].

On the other hand, if leakage current occurs downstream of the adjustment device 166, for example in the electric motor 22, the leakage current passes through the vehicle body 12, the ground wire 40, and the branch wire 45a, bypasses the ground side current transformer 182, merges with the ground side electric wire 45, and returns to the adjustment device 166. This allows the difference Ad between the current value A1 of the supply side current transformer 181 and the current value A2 of the ground side current transformer 182 to be calculated with high accuracy as the leakage current value. Therefore, the leakage current monitoring device 180 can improve the detection accuracy of leakage current occurring downstream of the adjustment device 166 by monitoring the current values A1 and A2 of the supply side current transformer 181 and the ground side current transformer 182.

The battery current transformer 183 measures the current value of the positive electrode wire 165a extending from the battery 165. Since current from the battery 165 and current from the generator 161 flow through the supply line 18, the current value A1 for the battery 165 and the current value for the generator 161 can be calculated from the current value A1 of the supply side current transformer 181 and the current value of the battery current transformer 183. This makes it possible to detect the occurrence of leakage current based on the current from the battery 165 or the occurrence of leakage current based on the current from the generator 161.

The specific control method of the leakage current monitoring device 170 is substantially the same as that of the leakage current monitoring device 80 of the first embodiment, except that the potential difference V1 is not acquired, and the difference between the current value A1 and the current value A2 is set to the difference Ad (the value of the leakage current) without being corrected by the potential difference V1, and the current value of the storage battery current transformer 183 is stored in the peak detection memory 82c or the like.

The present invention has been described above based on the embodiments, but the present invention is not limited to the above-mentioned embodiments, and it can be easily imagined that various improvements and modifications are possible within the scope of the present invention. For example, the voltage of the overhead lines 4, 140 and the value of the output voltage from the SIV 30 may be changed as appropriate. The number of railcars 100a-100c that are coupled together may be changed as appropriate, and part of a train formation in which multiple railcars are coupled together may be railcars 10, 150, 160.

The interval for acquiring the current values A1 and A2, the interval for acquiring the driving state data, the interval for calculating the average value of the difference Ad, the range of the difference Ad used to calculate the average value, the storage capacity of each ring buffer 83a to 83d, etc. may be changed as appropriate. The average value before the change used to calculate the short-term change rate and the long-term change rate in the average detection process S29 in FIG. 9 may be changed as appropriate. For example, the rate of change of the average value over the most recent minute relative to the average value 5 to 4 minutes ago (the average value obtained by averaging multiple difference Ad calculated 5 to 4 minutes ago) may be used as the short-term change rate and the long-term change rate.

In addition, the detailed electrical circuits of each part of the railway vehicles 10, 100a-100c, 150, 160 may be modified as appropriate. The railway vehicles 10, 100a-100c, 150 may be configured to be able to switch between DC and AC trains depending on the line they are traveling on, rather than just being either DC or AC trains. In this case, the supply side current transformer and ground side current transformer capable of detecting DC and the supply side current transformer and ground side current transformer capable of detecting AC are configured to be able to be switched depending on the power supplied to the railway vehicles 10, 100a-100c, 150 from the overhead lines 4, 140.

In the above embodiment, the leakage current monitoring devices 80, 110, 170, 180 are used to monitor the leakage current of the electrical circuits of the railroad cars 10, 100a-100c, 150, 160, but this is not limited to the above. The leakage current of electrical circuits other than the railroad cars 10, 100a-100c, 150, 160 may be monitored by the leakage current monitoring devices 80, 110, 170, 180. For example, electrical circuits other than the railroad cars 10, 100a-100c, 150, 160 include indoor wiring or electrical equipment in homes, facilities, factories, etc., electrical circuits in automobiles, aircraft, ships, and electrical appliances.

In the above embodiment, the railcars 10, 100a-100c, 150, and 160 run on rails 2, but the present invention is not limited to this. For example, the present invention may be applied to a railcar suspended from a rail. Also, in a DC train, instead of control by the VVVF inverter 20, the DC motor may be operated by resistance control that adjusts the DC power from the supply line 18 by voltage division and outputs it.

In the above embodiment, a three-phase, four-wire AC generator 161 is mounted on the railcar 160, but this is not limiting. The generator 161 may be changed to a single-phase AC generator or a three-phase, three-wire AC generator, and the AC power from the generator 161 may be converted to DC power by the adjustment device 166. The generator 161 may also be changed to a DC generator including a fuel cell, and the power conversion function by the adjustment device 166 may be omitted. The present invention may also be applied to a railcar that runs on only the storage battery 165 without a generator. Furthermore, the present invention may also be applied to a railcar that is equipped with both various types of generators or storage batteries 165 and a pantograph 17, and is capable of switching the power supply from them.

Also, the SIV 30 and the upstream side of the SIV 30 may be an on-board power source, and the three electric wires 32u, 32v, and 32w to which power is supplied from the on-board power source may be passed through three current transformers individually. Of the three electric wires 32u, 32v, and 32w, the one that is not connected to the ground wire 40 is a supply line, and the current transformer through which the supply line passes is a supply-side current transformer. If any of the three electric wires 32u, 32v, and 32w is connected to the ground wire 40, the connected one is a part of the ground wire, and the current transformer through which the part of the ground wire passes is a ground-side current transformer. Similarly, the VVVF inverter 20, the isolation transformer 34, the main transformer 151, the AC/DC converter, and the upstream side of these may be an on-board power source, and each electric wire on the downstream side (output side) of the on-board power source may be passed through a supply-side current transformer or a ground-side current transformer as appropriate.

In the above fourth embodiment, a case has been described in which the leakage current monitoring devices 170, 180 do not include a potential difference detection unit 89 that measures the potential difference V1, but this is not limited to the above. For example, the leakage current monitoring device 180 may be provided with a potential difference detection unit 89 that measures the potential difference V1 between the supply line 18 and the ground line 40, and the difference Ad corrected by the potential difference V1 may be calculated.

Similarly, the leakage current monitoring device 170 may be provided with a potential difference detection unit 89 that detects voltage cross points between the phases of the supply lines 162, 163, and 164 through which three-phase AC flows, and the leakage current Igr may be calculated as the corrected difference Ad. Note that, in order to calculate the leakage current Igr, if the target for detecting voltage cross points is a three-phase, three-wire system, the potential difference detection unit 89 may simply detect the voltage cross points between two ungrounded phases.

The potential difference detection unit 89 of the leakage current monitoring device 80, 110 in the first to third embodiments may be omitted. If a voltmeter that measures the voltage of the overhead line 4 is installed on the railway vehicle 10, 100a to 100c, 150, the voltmeter may be used as the potential difference detection unit 89.

In the above embodiment, the case where the potential difference between the ground terminal portion 43 and the rail 2 (each wheel 13) is assumed to be 0 [V] has been described, but this is not limited to the above. A second potential difference detection unit that measures the potential difference V2 between the ground terminal portion 43 and the rail 2 (each wheel 13) may be provided in the leakage current monitoring device 80, 110, 170, 180. For example, the difference between the current values A1 and A2 may be corrected using this potential difference V2 and the potential difference V1 by the potential difference detection unit 89.

In the above embodiment, the leakage current monitoring device 80, 110, 170, 180 calculates the difference Ad (leakage current value) based on the current values of the supply side current transformers 87, 87a, 87c, 171-173, 181 and the ground side current transformers 88, 88a-88c, 182, but this is not limited to the above. For example, the leakage current monitoring device 80, 110, 170, 180 may not calculate the difference Ad, but may calculate the difference Ad in the external server 90. In other words, the leakage current monitoring device 80, 110, 170, 180 may only transmit the current values of the supply side current transformers 87, 87a, 87c, 171-173, 181 and the ground side current transformers 88, 88a-88c, 182 and the potential difference V1 by the potential difference detection unit 89 to the external server 90. Also, without providing an external server 90, analysis based on the difference Ad and driving condition data may be performed by the leakage current monitoring devices 80, 110, 170, and 180.

In the above embodiment, the memory 82c to 82f in which data permitted to be transmitted to the external server 90 is stored stores the difference Ad itself or the average value of the difference Ad as data related to the difference Ad, but this is not limited to the above. The current values A1 and A2 may be stored in the memory 82c to 82f as data related to the difference Ad, and the current values A1 and A2 selected based on the difference Ad may be transmitted to the external server 90.

In addition, when the external server 90 and the leakage current monitoring devices 80, 110, 170, and 180 are capable of communicating with each other via the wireless communication device 71, data that is determined to be permitted to be transmitted to the external server 90 based on the difference Ad may be transmitted directly to the external server 90 without being stored in each of the memories 82c to 82f.

Each of the memories 82c to 82f may be provided in the HDD 62 of the railway vehicles 10, 100a to 100c, 150, and 160, and data in each of the memories 82c to 82f may be transmitted from the railway vehicles 10, 100a to 100c, 150, and 160 to the external server 90. Furthermore, the running state ring buffer 83a may be provided in the HDD 62 or RAM 63 of the railway vehicles 10, 100a to 100c, 150, and 160.

In addition, it is not necessary to store the driving condition data together with the difference Ad itself or the average value of the difference Ad in each of the memories 82c to 82f. In this case, the driving condition data stored in the driving condition ring buffer 83a and the data stored in each of the memories 82c to 82f are associated with each other by the measurement time (calculation time) of each data. Therefore, when transmitting the data stored in each of the memories 82c to 82f to the external server 90, it is sufficient to transmit to the external server 90 the driving condition data measured (acquired) at the same time as the measurement time of the data.

In the above embodiment, the current values of the supply side current transformers 87, 87a, 87c, 171-173, 181 and the ground side current transformers 88, 88a-88c, 182 are digitized and acquired in the CPU 81 of the leakage current monitoring device 80, 110, 170, 180, but this is not limited to the above. For example, the current values of the supply side current transformers 87, 87a, 87c, 171-173, 181 and the ground side current transformers 88, 88a-88c, 182 may be combined as analog signals, and the difference (sum) between these current values may be digitized and acquired by the CPU 81. In addition, when digitizing the current values of the supply side current transformers 87, 87a, 87c, 171-173, 181 and the ground side current transformers 88, 88a-88c, 182, and the potential difference V1 detected by the potential difference detector 89, the digitizing converter may communicate wirelessly with the input/output port 85.

In the above embodiment, the leakage current monitoring devices 80, 110, 170, and 180 are described as executing the peak detection process S28, the average detection process S29, and the cycle collection process S30, but this is not limited to the above. For example, at least one of the peak detection process S28, the average detection process S29, and the cycle collection process S30 may be executed, and the other processes may not be executed.

In the above embodiment, the case where the difference Ad from the start position S to the end position E is stored in the peak detection memory 82c in the peak detection process S28 has been described, but this is not limited to the above. For example, when the difference Ad of the latest position in the difference ring buffer 83b changes from less than the threshold to equal to or greater than the threshold, the difference Ad from 15 seconds ago to the latest position may be stored in the peak detection memory 82c, and the newly calculated difference Ad of the latest position may be stored in the peak detection memory 82c in each peak detection process S28 until 15 seconds have passed since the difference Ad changed from equal to or greater than the threshold to less than the threshold.

In the above first to third embodiments, the case where the aggregated wire 42 is passed through the ground side current transformers 88, 88a to 88c has been described, but this is not limited to the above. For example, the ground side electric wire 45 may be passed through the ground side current transformers 88, 88a to 88c, so that only the leakage current on the input side of the VVVF inverter 20 and the SIV 30 can be detected.

In the fourth embodiment, a current transformer through which the aggregated line 42 passes may be added to the leakage current monitoring devices 170 and 180. For example, a current transformer through which the aggregated line 42 passes can detect stray current passing through the aggregated line 42, so that the effect of the stray current can be eliminated to analyze the leakage current.

In the above first and second embodiments, the isolation transformer 34 converts the three-phase AC of the first low-voltage AC circuit 32 into single-phase three-wire AC and outputs it to the second low-voltage AC circuit 36, but this is not limited to the above. For example, the isolation transformer 34 may be configured to convert (transform) the three-phase AC into three-phase four-wire AC, and the second low-voltage AC circuit 36 may be configured to extract 100V single-phase AC between one neutral wire (wire 36n) connected to the ground wire 40 and each of the three wires (wires 36r, 36t and an additional wire) that are not connected to the ground wire 40.

Also, single-phase AC may be extracted from the three-phase AC of the first low-voltage AC circuit 32, and the extracted single-phase AC may be transformed by the isolation transformer 34 and output to the second low-voltage AC circuit 36. Specifically, for example, the primary winding of the isolation transformer 34 may connect the wire 32v of the first low-voltage AC circuit 32 and the ground wire 40, and the secondary winding of the isolation transformer 34 may connect the wire 36r of the second low-voltage AC circuit 36 and the ground wire 40 (wire 36n).

In the third embodiment, the first low-voltage AC circuit 32 is connected to the tertiary winding of the main transformer 151, but this is not limited to the above. The tertiary winding of the main transformer 151 may be omitted, and the SIV 30 in the first and second embodiments may be mounted on the railway vehicle 150, and the first low-voltage AC circuit 32 may be connected to the SIV 30. In this case, the positive and negative electric wires connecting the output side of the AC/DC converter 152 and the input side of the VVVF inverter 20 are each branched, and the branched positive and negative electric wires are each connected to the input side of the SIV 30.

In the above embodiment, the supply side current transformers 87, 87a, 87c, 171-173, 181, the ground side current transformers 88, 88a-88c, 182, and the storage battery current transformer 183 are each configured as annular current transformers through which the electric wire to be measured passes, and are measuring instruments that measure the value of the current flowing through the passing part. However, these current transformers may be replaced with other measuring instruments that can measure the value of the current flowing through the electric wire to be measured. An example of the other measuring instruments is a non-annular one that measures the magnetic field generated in the electric wire when current is passed through it, and measures the value of the current based on that magnetic field. Another example of the other measuring instruments is limited to those that measure the current of one electric wire individually, but an example is one that uses a shunt resistor.

2 Rail 4, 140 Overhead line 10, 100b, 150, 160 Railway vehicle 100a, 100c Railway vehicle (power supply vehicle)
13 Wheel 14 Connection portion 15 Three-phase AC device (a type of electrical device)
16. Single-phase AC equipment (a type of electrical equipment)
17 Pantograph 18, 162, 163, 164 Supply line 18a Supply lead-in line 18b Supply upstream line 19 DC equipment (a type of electrical equipment)
20 VVVF inverter (a type of electrical device)
22 Electric motor (a type of electrical equipment)
30 SIV (a type of electrical equipment)
34 Isolation transformer (part of electrical equipment)
40 Ground wire 41 Ground lead-through wire 42 Aggregated wire 43 Ground terminal portion 71 Wireless communication device (transmitter)
80, 110, 170, 180 Leakage current monitor (monitoring device)
87, 87a, 87c, 171, 172, 173, 181 Supply side current transformer (supply side measuring instrument)
88, 88a, 88b, 88c, 182 Earth side current transformer (earth side measuring instrument)
89 Potential difference detection unit 151 Main transformer (a type of electrical equipment)
152 AC/DC converter (a type of electrical equipment)
161 Generator (on-board power supply)
161a Neutral wire 165 Storage battery (onboard power supply)
166 Adjustment device (a type of electrical equipment)
S26, S48, S51, S65, S68, S72 Potential correlation means S21 Acquisition means S48, S51, S65, S68, S72 State correlation means S26 Difference calculation means S41 to S47, S50, S63, S64, S66, S67 Transmission decision means S48, S51, S65, S68 Transmission permission means

Claims (9)

A railway vehicle that is equipped with at least one of a pantograph that receives power from an overhead line and an on-board power source other than a three-phase four-wire power source that generates power for running the vehicle and runs on rails,
A plurality of wheels that roll on the rail;
A ground wire connected to the wheel and grounded;
a supply line to which power is supplied from the pantograph or the on-board power supply;
an electric device connected to an electric circuit including the supply line and the ground line and operated by power from the supply line;
A monitoring device for monitoring a leakage current occurring in the electric circuit,
The monitoring device is
a supply side meter that measures a current value of the supply line;
A ground side measuring instrument that measures a current value of the ground wire;
A railway vehicle comprising: a pair of coupling parts provided at both ends of the rail vehicle in a rail direction and capable of being coupled to another vehicle;
The supply line is
A supply line that is passed between the pair of coupling parts and can be connected to the other vehicle;
and an upstream supply line connecting the supply line and the pantograph or the on-board power source,
2. The railway vehicle according to claim 1, wherein the supply side measuring instrument measures a current value of the upstream supply line. a pair of coupling parts provided at both ends of the rail vehicle in a rail direction and capable of being coupled to another vehicle;
The ground wire is
a grounding line that is routed between the pair of coupling portions and is connectable to the other vehicle and to which the electrical equipment is connected;
A central line branching off from the grounding line;
a ground terminal portion that connects the wheels to the collective line so that the wheels are at the same potential;
2. The railway vehicle according to claim 1, wherein the ground side measuring instrument measures a current value of the aggregated line. The monitoring device includes:
a potential difference measuring unit that measures a potential difference between the supply line and the ground line;
a potential correlation means for correlating the potential difference measured by the potential difference measuring unit with the current values of the supply-side measuring instrument and the ground-side measuring instrument at the time of measurement;
2. The railway vehicle according to claim 1, further comprising: The monitoring device includes:
An acquisition means for acquiring a running state of the railway vehicle;
a state relating means for relating the driving state obtained by the obtaining means to the current values of the supply side meter and the ground side meter at the time of obtaining the driving state;
2. The railway vehicle according to claim 1, further comprising: The railway vehicle according to claim 1, further comprising a transmission unit that transmits data on the current values measured by the supply side meter and the ground side meter to the outside of the railway vehicle. The monitoring device includes:
a difference calculation means for calculating a difference between a current value of the supply side measuring device and a current value of the ground side measuring device;
a transmission determination means for determining whether or not to transmit data relating to the difference calculated by the difference calculation means from the transmitter to an outside of the railway vehicle;
a transmission permission means for allowing data relating to the difference to be transmitted from the transmitting unit to an outside of the railway vehicle when the transmission determination means determines that the data should be transmitted;
7. The railway vehicle according to claim 6, further comprising: A railway vehicle that runs on a rail receiving power from the power supply car according to any one of claims 1 to 7 in a train configuration,
A plurality of wheels that roll on the rail;
A coupling part coupled to the power supply vehicle directly or via another vehicle;
an electric device operated by power supplied from the power supply vehicle through the connection part;
A vehicle grounding wire that connects the electrical equipment to the wheel and grounds it;
and a vehicle ground side measuring instrument that measures a current value of the vehicle ground wire. A railway vehicle that runs on rails,
A plurality of wheels that roll on the rail;
A ground wire connected to the wheel and grounded;
an on-board power supply that is a three-phase, four-wire power supply having a neutral wire connected to the ground wire and that generates power for running the vehicle;
Three supply lines to which power is supplied from the on-board power supply;
an electric device connected to an electric circuit including the supply lines and operated by power from the supply lines;
a monitoring device for monitoring a leakage current occurring in the electric circuit and passing through the neutral conductor;
The monitoring device of the railway vehicle is characterized in that it includes three supply-side measuring instruments that individually measure the current values of the three supply lines.

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