JP6969079B2 - Forced installation device, ground fault investigation device and method using it - Google Patents

Description

The present invention is a forced grounding device that generates an exploration current for exploring a ground fault in a DC power supply circuit that supplies DC power to a sequence circuit for operating electrical equipment in an electric facility, and a ground fault using the same. Regarding fault search equipment and methods.

Electric stations such as power generation / transformation stations and switch stations are provided with a DC power supply circuit that supplies DC power to a sequence circuit for operating electric devices such as circuit breakers and disconnectors. A plurality of DC power supply circuits are drawn from the DC bus to which the DC power supply device is connected, and further branch off from the DC power supply circuit to supply DC power to a sequence circuit which is a large number of DC loads.

In such a DC power supply circuit, a DC ground relay (64D) for detecting a ground fault in the DC power supply circuit is installed. The DC ground relay is provided in a voltage dividing circuit in which the positive and negative electrodes of the DC bus of the DC power supply circuit are divided by resistance, and the voltage dividing middle point of the voltage dividing circuit is grounded via a resistor.

If insulation deteriorates in any of these DC power supply circuits and a ground fault occurs, the DC ground relay operates so that it can be detected that a ground fault has occurred, but the location of the ground fault failure. Cannot be specified. Therefore, when it is detected that a ground fault has occurred, the location of the ground fault will be searched. There are flicker method and low frequency superimposition method as a method for exploring the location of a ground fault.

FIG. 10 is a circuit diagram of a DC circuit of a DC power supply circuit that supplies DC power to a sequence circuit of an electric station. In the DC circuit of the electric station, DC power is supplied from the DC bus 12 to which the DC power supply device 11 is connected to the plurality of DC power supply circuits 15a to 15n via the switch 14 of the DC power supply panel 13, respectively, and the sequence circuits 16a to A DC power supply is supplied to 16n. C in FIG. 10 shows the ground capacitance of the electric wires of the DC power supply circuits 15a to 15n.

Further, each DC power supply circuit 15a to 15n has a plurality of branch circuits 17. In FIG. 10, the DC power supply circuit 15a has one branch circuit 17, and the DC power supply circuits 15b and 15n have two branch circuits 17. Although not shown, the branch circuit 17 also has a branch circuit, and a sequence circuit is connected to each branch circuit to have a capacitance to ground of the electric wire. On the other hand, between the positive and negative sides of the bus 12 of the DC circuit, a voltage dividing circuit 18 is installed in which the positive voltage and the negative voltage are divided by resistance and the middle point of the voltage dividing is grounded by resistance. It constitutes an element of the DC ground fault relay 19 that detects a ground fault, and the DC ground fault relay 19 operates when the voltage of the voltage dividing circuit 18 is out of balance.

When a ground fault occurs in the DC circuit of such an electric place, a DC ground fault current flows. For example, assuming that a ground fault of the ground fault resistance Rg occurs at point F of the DC power supply circuit 15b, as shown by the dotted arrow in FIG. 10, the switch 14 of the DC power supply panel 13 is connected to the positive electrode of the DC power supply device 11. A circuit is formed up to the ground fault failure point F, the grounding point (neutral wire) of the voltage dividing circuit 18, and the negative electrode of the DC power supply device 11, and a DC ground fault current flows. As a result, the voltage balance of the voltage dividing circuit 18 is lost and the DC ground relay relay 19 operates, so that it can be seen that a ground fault has occurred in any of the DC power supply circuits 15a to 15n. Further, in order to search for the ground fault point F, it is investigated whether or not a DC ground fault current is flowing in each of the DC power supply circuits 15a to 15n, and the DC power supply in which the ground fault has occurred is supplied. The circuits 15a to 15n are specified, and the location of the ground fault failure is specified. In this case, the AC fault current can be easily detected by the AC current clamp meter, but it is difficult to detect the DC ground fault current.

Therefore, when it is detected that the DC ground relay relay 19 operates and a ground fault has occurred, the ground fault point F can be searched for using an AC current clamp meter by the low frequency superimposition method or the flicker method. There is. In the low-frequency superimposition method, a low-frequency AC current is forcibly passed through each of the DC power supply circuits 15a to 15n, and a ground fault failure point is determined by the presence or absence of the probe current of the passed AC current and the change state by the AC current clamp meter. In the flicker method, a flicker device is connected to the grounding point of the voltage dividing circuit 18, the flicker contacts of the flicker device are intermittently turned on and off to generate an exploration current from the DC power supply device 11, and an AC current clamp is used. This is a method of exploring the ground fault point F by measuring the flowed exploration current with a meter.

FIG. 11 is an explanatory diagram in the case of searching for a ground fault failure point of a DC power supply circuit by a low frequency superimposition method. As in FIG. 10, if a ground fault of the ground fault resistance Rg occurs at point F of the DC power supply circuit 15b, the DC ground relay relay 19 operates and a ground fault occurs in any of the DC power supply circuits 15a to 15n. It can be seen that a failure has occurred. When searching for the ground fault point F by the low frequency superimposition method, a low frequency AC power supply device 20 is connected to the grounding point (neutral line) of the voltage dividing circuit 18, and the low frequency AC power supply device 20 is used to connect the low frequency AC power supply device 20. The AC exploration current is supplied to the DC power supply circuits 15a to 15n. Then, as shown by the dotted arrow in FIG. 11, the ground resistance of the voltage divider circuit 18 from the low frequency AC power supply device 20, the voltage divider resistance on the positive side of the voltage divider circuit 18, the switch 14bp of the DC power supply panel 13, and the ground fault. A circuit is formed to reach the failure point F and the grounding point of the low-frequency AC power supply device 20, and the exploration current Ipg flows through the ground fault resistance Rg.

Further, since the exploration current is an alternating current, the low frequency alternating current power supply device 20 to the ground resistance of the voltage dividing circuit 18, the voltage dividing resistance on the positive side of the voltage dividing circuit 18, the switch 14bp of the DC power supply panel 13, and the DC power supply. A circuit is formed up to the ground capacitance Cbp of the electric wire of the supply circuit 15b and the grounding point of the low-frequency AC power supply device 20, and the exploration current Ipc flows through the ground capacitance Cbp. Further, from the low frequency AC power supply device 20, the ground resistance of the voltage dividing circuit 18, the voltage dividing resistance on the negative side of the voltage dividing circuit 18, the switch 14bn of the DC power supply panel 13, and the ground electrostatic capacity of the electric wire of the DC power supply circuit 15b. A circuit is formed up to the grounding point of the low frequency AC power supply device 20 at Cbn, and the exploration current Inc flows through the ground capacitance Cbn.

To search for the ground fault point F, for each of the DC power supply circuits 15a to 15n, the branch circuit 17 downstream of the DC power supply circuit 15 is branched from the location near the DC power supply board 13 (near the DC bus 12). The AC current clamp meter 21 is sequentially moved to the points, sandwiched between the electric wires of the DC power supply circuit 15, and clamped to measure the exploration current. In the DC power supply circuit 15b where the ground fault point F is generated, the AC exploration current I1 is the exploration current Ipg flowing through the ground fault resistance Rg, the exploration current Ipc flowing through the ground capacitance Cbp, and the ground static. Since the exploration current I1 (= Ipg + Ipc + Inc), which is the sum of the exploration currents Inc flowing in the electric capacity Cbn, flows, when the AC current clamp meter 21 is clamped to the electric wire near the DC bus 12 of the DC power supply circuit 15b, the AC current The clamp meter 21 will measure this exploration current I1.

Next, when the AC current clamp meter 21 is clamped to the electric wire in front of the branch point of the branch circuit 17b of the DC power supply circuit 15b, it is a location that has passed the ground fault failure point F. As the AC exploration current I2, the exploration current I2 (= Ipc + Inc), which is the sum of the exploration current Ipc flowing through the ground capacitance Cbp and the exploration current Inc flowing through the ground capacitance Cbn, flows.

As described above, the exploration current I1 includes the exploration current Ipg flowing through the ground fault resistance Rg, but the exploration current I2 does not include the exploration current Ipg flowing through the ground fault resistance Rg. From this, the presence or absence of the component including the ground fault resistance Rg can be determined from the current vectors of the exploration current I1 and the exploration current I2, and the location of the ground fault failure point F can be specified. That is, it can be seen that there is a ground fault point F downstream of the electric wire in the vicinity of the DC bus 12, and there is no ground fault point F downstream of the electric wire before the branch point of the branch circuit 17b of the DC power supply circuit 15b. Therefore, it is determined that there is a ground fault point F during this period.

FIG. 12 is an explanatory diagram when searching for a ground fault point of a DC power supply circuit by the flicker method. As in FIG. 10, if a ground fault of the ground fault resistance Rg occurs at point F of the DC power supply circuit 15b, the DC ground relay relay 19 operates and a ground fault occurs in any of the DC power supply circuits 15a to 15n. It can be seen that a failure has occurred. When searching for the ground fault point F by the flicker method, the flicker device 22 is connected to the grounding point (neutral wire) of the voltage dividing circuit 18, and the flicker contact of the flicker device 22 is intermittently turned on and off from the DC power supply device 11. The exploration current of the rectangular wave pulsating current is generated, and the exploration current of the rectangular wave pulsating current is supplied to the DC power supply circuits 15a to 15n.

Then, when the flicker contact of the flicker device 22 is on, the grounding point (neutral wire) of the voltage dividing circuit 18 is in a grounded state. Therefore, as shown by the dotted arrow in FIG. 12, the DC power supply circuit 11 A circuit is formed from the positive electrode to the switch 14bp of the DC power supply panel 13, the ground fault failure point F, the flicker contact (grounding point) of the flicker device 22, the voltage dividing resistance of the voltage dividing circuit, and the negative voltage of the DC power supply circuit 11. The exploration current Ipg flows through the ground fault resistance Rg.

Although not shown, the exploration current is the exploration current of the square wave pulsating current, so the exploration current Ipc flows through the ground capacitance Cbp at the rising and falling portions of the square wave, and the ground capacitance Exploration current Inc flows through Cbn.

In order to search for the ground fault point F, as described above, for each of the DC power supply circuits 15a to 15n, alternating current is sequentially applied from the vicinity of the DC bus 12 to the branch point of the branch circuit 17 downstream of the DC power supply circuit 15. The current clamp meter 21 is moved and clamped to the electric wire of the DC power supply circuit 15 to measure the exploration current.
Here, in the DC power supply circuit 15b where the ground fault point F is generated, the exploration current Ipg flowing through the ground fault resistance Rg and the exploration current flowing through the ground capacitance Cbp are used as the exploration current I1 of the rectangular wave pulse flow. The exploration current I1 (= Ipg + Ipc + Inc), which is the sum of the exploration currents Inc flowing in the Ipc and the ground capacitance Cbn, flows, but the exploration current Ipc flowing in the ground capacitance Cbp and the exploration current Inc flowing in the ground capacitance Cbn are rectangular. It is the current that flows in the rising and falling parts of the wave pulse flow, and it is added because the positive and negative polarities of the exploration current Ipc flowing in the ground capacitance Cbp and the exploration current Inc flowing in the ground capacitance Cbn are opposite. Sometimes it is offset.

Therefore, the exploration current I1 measured by the AC current clamp meter 21 is the exploration current Ipg flowing through the ground fault resistance Rg. When the AC current clamp meter 21 is clamped to the electric wire in the vicinity of the DC bus 12 of the DC power supply circuit 15b, the AC current clamp meter 21 measures the exploration current I1. Since the exploration current I1 is the exploration current Ipg flowing through the ground fault resistance Rg and is the exploration current of the square wave pulsating current, the AC current clamp meter 21 has the size of the rising portion or the falling portion of the rectangular wave pulsating current. Determine the presence or absence of exploration current.

Next, when the AC current clamp meter 21 is clamped to the electric wire in front of the branch point of the branch circuit 17b of the DC power supply circuit 15b, it is a location that has passed the ground fault failure point F. , There is no exploration current Ipg flowing through the ground fault resistance Rg. From this, the location of the ground fault failure point F can be specified by determining the components of the exploration current Ipg flowing through the ground fault resistance Rg in the exploration current I1 and the exploration current I2. That is, since the exploration current I1 contains a component of the exploration current Ipg flowing through the ground fault resistance Rg, there is a ground fault failure point F downstream of the electric wire in the vicinity of the DC bus 12, and the branch circuit 17b of the DC power supply circuit 15b. Since there is no component of the exploration current Ipg flowing through the ground fault resistance Rg downstream of the electric wire in front of the branch point, it can be seen that there is no ground fault failure point F. Therefore, it is determined that there is a ground fault failure point F during this period.

Here, when the DC ground relay for ground fault detection of a DC electric circuit in which a plurality of load circuits are connected in parallel detects a ground fault current, the flicker relay opens and closes the relay contact to open and close the ground fault current. Is converted into a rectangular wave pulsating current and output, and when searching for a DC grounding point by detecting the rectangular wave pulsating current with a detector, an AC waveform current feedback unit is added to the circuit of the rectangular wave pulsating current detector. Some of them are connected to improve the detection accuracy of rectangular wave pulsating current (see, for example, Patent Document 1).

Tokuho 5-35384 Gazette

However, in the search for the ground fault point by the low frequency superimposition method, the search current is found when the ground fault resistance Rg of the ground fault point is large or when the ground capacitance of the electric wire of the DC power supply circuit 15 is large. Detection accuracy is reduced. This is because when the ground fault resistance Rg at the ground fault failure point is large, the exploration current becomes small, and when the capacitance to ground is large, the exploration current becomes relatively small and falls within the range of the detection error. That is, in order to reduce the influence of the capacitance to ground, the AC exploration current must be set to a low frequency, and the sensitivity of the AC current clamp meter, which is proportional to the frequency of the exploration current and the detection accuracy, is naturally low. The detection sensitivity of the entanglement failure was also low.

In addition, since the exploration current is the exploration current of the square wave pulsating current in the search for the ground fault point by the flicker method, the AC current clamp meter uses the size of the rising or falling part of the square wave pulsating current as the exploration current. Since it is determined whether or not the current is present, the detection accuracy cannot be improved unless the exploration current is increased to some extent.

Further, in Patent Document 1, the feedback portion of the AC waveform current is connected to the circuit of the square wave pulsating current detector (AC current clamp meter) to improve the detection accuracy of the square wave pulsating current. In the exploration of the ground fault point by the method, the presence or absence of the exploration current is determined by the size of the rising portion or the falling portion of the square wave pulsating current, so that there is a limit to the improvement of the detection accuracy.

An object of the present invention is a forced grounding device that generates an exploration current that can safely and accurately search for a ground fault in a DC power supply circuit that supplies DC power to a sequence circuit for operating electrical equipment in an electric facility. It is to provide the ground fault search device and method used.

In the forced grounding device according to the invention of claim 1, a ground fault has occurred in any of a plurality of DC power supply circuits that supply DC power from the DC power supply device to the sequence circuit for operating the electric equipment of the electric station. when, at the time of probing the ground fault point by detecting a DC exploration current wire is clamped to adjust the zero point of the DC power supply circuit is supplied from the DC power supply apparatus by the DC current clamp meter cracking line, Used in a state where the midpoint of the voltage dividing circuit between the positive and negative sides of the DC bus of the DC power supply circuit to which the DC ground fault relay for detecting the ground fault and the faulty electrode is connected is ungrounded. This is a forced grounding device, and when the ground fault failure and the fault electrode are detected by the DC ground fault relay, the sound pole of the positive and negative working terminals of the DC power supply circuit in which the ground fault has occurred. of the limiting resistor connected to the working terminals is limited to a size that sequence circuit the magnitude of the probe current does not malfunction, said limiting resistor connected in series when the zero point adjustment of the DC current clamp meter Turn off to make the limiting resistance ungrounded, and when the DC current clamp meter searches for the ground fault point, turn it on to ground the limiting resistance and supply DC exploration current from the DC power supply device to the DC power supply. It is characterized by being equipped with a forced ground switch for supplying to the circuit.

The forced grounding device according to the second aspect of the present invention is characterized in that, in the first aspect of the present invention, the ammeter is connected in series to the forced grounding switch and measures the current flowing through the forced grounding switch.

The forced grounding device according to the third aspect of the present invention is characterized in that, in the first or second aspect of the present invention, the forced grounding switch is provided with an on / off control unit that turns the forced grounding switch on and off at regular intervals.

The forced grounding device according to the fourth aspect of the present invention is characterized in that, in the third aspect of the present invention, the forced grounding device has a notification unit for notifying that the forced grounding switch is on.

The ground fault search device according to the invention of claim 5 is clamped to the forced grounding device according to any one of claims 1 to 4 and the electric current of the DC power supply circuit to adjust the zero point, and then the zero point is adjusted. It is characterized by being equipped with a DC current clamp meter that detects a DC exploration current supplied from a DC power supply device.

The ground fault fault search method according to the invention of claim 6 is a ground fault failure by a DC ground fault relay to any of a plurality of DC power supply circuits that supply DC power to a sequence circuit for operating electrical equipment of an electric station. And when the faulty pole is detected, the faulty pole and the healthy pole of the DC power supply circuit in which the ground fault has occurred are determined based on the operation content of the DC ground fault relay, and the DC to which the DC ground fault relay is connected is determined. The midpoint of the voltage dividing circuit between the positive and negative sides of the DC bus of the power supply circuit is ungrounded, and DC is applied to the working terminal of the DC bus of the sound pole of the positive and negative electrodes of the DC power supply circuit. force ground for forming a circuit extending to the negative electrode to generate a probe current of a direct current of a positive electrode the DC power supply device through the working terminals of the ground fault point and the sound pole from the power supply flows to the DC power supply circuit The DC current clamp meter is clamped to the electric wire of the DC power supply circuit near the DC bus in a state where the device is connected, the forced ground switch of the forced grounding device is turned off, and the exploration current is not generated. Is adjusted to the zero point, and after the zero point adjustment, the forced grounding switch of the forced grounding device is turned on to generate the exploration current and enable the detection of the exploration current by the DC current clamp meter. When the exploration current is not detected, the DC current clamp meter is sequentially moved to the vicinity of the DC bus of another DC power supply circuit among the plurality of DC power supply circuits, and the exploration is repeated until the exploration current flows. When the presence or absence of a current is determined and the DC current clamp meter detects the exploration current, the DC current clamp meter is sequentially moved to the branch point of the DC power supply circuit on the downstream side, and the exploration current stops flowing. The presence or absence of the exploration current is repeatedly determined up to the above point, and the ground fault is between the downstream side of the DC power supply circuit through which the exploration current flows and the upstream side of the DC power supply circuit in which the exploration current stops flowing. It is characterized in that it is determined that a failure has occurred.

According to the invention of claim 1, when searching for a ground fault of the DC power supply circuit, the voltage dividing circuit between the positive and negative sides of the DC bus of the DC power supply circuit to which the DC ground fault successor is connected With the voltage division midpoint ungrounded, the forced ground switch is turned off when adjusting the zero point of the DC current clamp meter , and the limiting resistor that limits the magnitude of the probe current is ungrounded, and the DC current clamp meter is set. When searching for a ground fault point, turn it on to ground the limiting resistor and supply the DC search current from the DC power supply to the DC power supply circuit, so the ground fault of the DC power supply circuit can be searched safely and accurately. It is possible to generate an exploration current that can be generated.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, the current meter displays the total value of the exploration currents flowing through the plurality of DC power supply circuits, and thus is displayed on the DC current clamp meter. By comparing with the value of the exploration current, it is possible to determine whether or not a ground fault has occurred in a circuit other than the DC power supply circuit under exploration with the DC current clamp meter.

According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, the forced grounding switch is turned on and off at regular intervals by the on / off control unit, so that the worker can turn on and off the forced grounding switch when the forced grounding switch is off. adjust the zero point of the direct current clamp meter, forcing the grounding switch can probe the ground fault point in direct current clamp meter when on. Therefore, it is not necessary for the worker to turn on / off the forced grounding switch, and the amount of work is reduced.

According to the invention of claim 4, in addition to the effect of the invention of claim 3, since the notification unit notifies that the forced grounding switch is on, the worker can easily grasp the on / off state of the forced grounding switch. Workability is improved.

According to the invention of claim 5, the forced grounding device according to any one of claims 1 to 4 is clamped to the electric wire of the DC power supply circuit to adjust the zero point, and then the DC is supplied from the DC power supply. Since the ground fault search device is configured by combining the DC current clamp meters that detect the search current of the above, it is possible to provide the ground fault search device having the effects of claims 1 to 4.

According to the invention of claim 6, connect the forced grounding device to the DC power supply circuit when the ground fault occurs in the DC power supply circuit, the earth by the DC current clamp meter by performing the zero point adjustment of the DC current clamp meter The search for entanglement failure is performed, the presence or absence of the search current is repeatedly determined up to the branch point where the search current does not flow, and the downstream side of the DC power supply circuit where the search current flows and the DC power supply circuit where the search current stops flowing. Since it is determined that a ground fault has occurred between the upstream side and the DC power supply circuit, the ground fault of the DC power supply circuit can be searched safely, accurately and efficiently.

It shows a state in which the forced grounding device according to the first embodiment of the present invention is applied to the DC power supply circuit of an electric place, and the DC current clamp meter is clamped to the DC power supply circuit 15a of the first stage to adjust the zero point. circuit diagram. The circuit diagram which shows the state which turned on the forced grounding switch of the forced grounding device after adjusting the zero point of a DC current clamp meter in the state of FIG. The circuit diagram which shows the state which clamped the DC current clamp meter to the DC power supply circuit 15b of the 2nd stage of the next stage, and performed the zero point adjustment. FIG. 3 is a circuit diagram showing a state in which the exploration current is supplied by turning on the forced grounding switch of the forced grounding device after adjusting the zero point of the DC current clamp meter in the state of FIG. FIG. 4 is a circuit diagram showing a state in which a DC current clamp meter is moved to an electric wire in front of a branch point of a DC power supply circuit and zero point adjustment is performed in the state of FIG. FIG. 5 is a circuit diagram showing a state in which the forced grounding switch of the forced grounding device is turned on and the exploration current is supplied after the zero point adjustment of the DC current clamp meter is performed in the state of FIG. The block diagram of the forced grounding apparatus which concerns on 2nd Embodiment of this invention. The flowchart which shows the ground fault fault search method which concerns on 3rd Embodiment of this invention (the 1). FIG. 2 is a flowchart showing a ground fault fault search method according to a third embodiment of the present invention. The circuit diagram of the DC circuit of the DC power supply circuit that supplies DC power to the sequence circuit of the electric place. Explanatory drawing when searching for the ground fault point of the DC power supply circuit by the low frequency superimposition method. Explanatory drawing when searching for the ground fault point of the DC power supply circuit by the flicker method.

The background to the present invention will be described. In the past, there was no high-sensitivity DC current clamp meter, so as described above, using the low-frequency superimposition method or flicker method, a low-frequency alternating current exploration current or rectangular wave pulsating current exploration current was used in the DC circuit. Was used to detect the exploration current with an AC current clamp meter. Therefore, there is a limit to the detection accuracy of the AC current clamp meter. That is, the measurement with the AC current clamp meter could not be performed unless the failure current to the extent that the DC ground relay (64D) continuously operates flows. In other words, the AC current clamp meter could not detect the exploration current unless a fault current of enough to continuously operate the DC ground relay (64D) flows due to the problem of sensitivity.

In recent years, high-sensitivity DC current clamp meters that can be read directly up to 10 microamperes have been developed and put on the market, and it is not impossible to directly measure the minute DC leakage current flowing at the ground fault point.

Therefore, we have developed a forced grounding device of the present invention for forcibly flowing an appropriate minute exploration current for exploration of a ground fault point, and have commercially available a DC current clamp meter (manufactured by Multi-Measuring Instrument Co., Ltd.). The ground fault probe of the present invention was developed by adopting a high-sensitivity DC clamp meter, M-730, DC 0 to 100 mA, and a resolution of 0.01 mA). This makes it possible to identify the failure point even if the DC ground relay operates once but does not continue to operate, or even if the DC ground relay does not operate.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a circuit diagram in which the forced grounding device according to the first embodiment of the present invention is applied to a DC power supply circuit of an electric place. In FIG. 1, a ground fault of the ground fault resistance Rg occurs at the F point of the positive electrode wire of the DC power supply circuit 15b, and the forced grounding device 23 is connected to the sound pole of the DC power supply circuit 15 in which the ground fault has occurred. It shows the case where it was done. That is, the connection to the healthy electrode of the DC power supply circuit 15 in which the ground fault has occurred is the healthy electrode (negative electrode) of the working terminals 25p and 25n of the working positive electrode and the negative electrode at the connection point to the DC bus 12. The case where it is connected to the work terminal 25n is shown. Further, the DC current clamp meter 24 can be read directly up to the above-mentioned 10 microampere order, and the DC current clamp meter 24 is clamped to the DC power supply circuit 15a to adjust the zero point of the DC current clamp meter 24. Shows. The same elements as those in FIG. 10 are designated by the same reference numerals, and duplicate description will be omitted.

Once a ground fault in the DC power supply circuit 15 of an electric station occurs, it is detected by the operation of the DC ground relay relay 19. Since the DC ground relay 19 detects and displays a faulty electrode, it is possible to determine whether a failure has occurred in the positive electrode or the negative electrode of the DC power supply circuit 15 by checking the faulty pole display of the DC ground relay. ..
The occurrence of a ground fault failure to the extent that the DC ground relay relay 19 does not operate and the identification of the failure electrode are confirmed by periodically measuring the voltage balance of the DC power supply circuit 15. The voltage balance of the positive and negative electrodes of the DC power supply circuit 15 is measured by measuring the voltage to ground of the positive and negative electrodes at the working terminals 25p and 25n. When the working terminals 25 are individually provided on the positive and negative electrodes of the DC power supply circuits 15a to 15n, the voltage balance between the positive and negative electrodes is measured for each working terminal 25 to obtain a healthy electrode. Can be identified. In the following description, a case where it is detected that a ground fault has occurred in any of the DC power supply circuits 15a to 15n of the electric station due to the operation of the DC ground relay relay 19 will be described. The occurrence of a ground fault in the DC power supply circuit 15 and the identification of the faulty pole are confirmed by checking the faulty pole display of the DC ground relay relay 19.

When it is detected that a ground fault has occurred in any of the DC power supply circuits 15a to 15n of the electric station due to the operation of the DC ground relay, the forced grounding device 23 detects the ground fault. It is used in a state where the voltage dividing midpoint of the voltage dividing circuit 18 of the relay electric device 19 is not grounded. This is because the forced grounding device 23 supplies a DC exploration current from the DC power supply device 11 to the DC power supply circuit 15, and is a voltage dividing midpoint of the voltage dividing circuit 18 which is a grounding point other than the ground fault failure point. This is to prevent the exploration current from flowing in. By making the voltage dividing midpoint of the voltage dividing circuit 18 ungrounded, the detection accuracy of the exploration current can be improved.

Here, when the working terminal 25 is individually provided on the positive electrode and the negative electrode of each DC power supply circuit 15a to 15n, it may be commonly provided on the positive electrode and the negative electrode of each DC power supply circuit 15a to 15n. , FIG. 1 shows working terminals 25p and 25n which are commonly provided. That is, for each of the DC power supply circuits 15a to 15n, a common working terminal 25p is provided on the positive electrode, and a working terminal 25n is commonly provided on the negative electrode.

In the following description, a case where the working terminal 25 is provided in common to the positive electrode and the negative electrode of the respective DC power supply circuits 15a to 15n will be described. That is, in FIG. 1, the forced grounding device 23 is common to the healthy electrodes of the working positive electrode and the working terminal 25 of the working positive electrode and the negative electrode at the connection point of the DC power supply circuit 15 where the ground fault has occurred to the DC bus 12. The case where it is connected to the work terminal 25n is shown.

The forced grounding device 23 is configured by connecting a limiting resistor 26 and a forced grounding switch 27 in series. The limiting resistor 26 is a resistor that limits the magnitude of the exploration current to such an extent that the sequence circuit 16 does not malfunction, and when the forced grounding switch 27 is on, the DC exploration current is supplied from the DC power supply device 11 to the DC power supply. It is a switch for supplying to the circuit 15. In FIG. 1, the forced grounding switch 27 is in the off state, and in this state, the DC exploration current is not supplied from the DC power supply device 11 to the DC power supply circuit 15.

Then, in order to search for the ground fault point F of the DC power supply circuit 15, with the forced grounding switch 27 turned off, DC power is supplied from the vicinity of the DC bus 12 for each of the DC power supply circuits 15a to 15n. The DC current clamp meter 24 is sequentially moved toward the branch point of the branch circuit 17 downstream of the circuit 15, and the zero point is adjusted each time the DC current clamp meter 24 is moved, and the exploration current is measured to identify the ground fault point.

Perform zero-point adjustment of the DC current clamp meter 24, since the DC current clamp meter 24 is for detecting a DC current flowing the AC bias to the secondary side, the measurement in order to correct the zero point offset This is because the zero point adjustment is required every time.

As shown in FIG. 1, the ground fault failure point F is sequentially searched from the DC power supply circuit 15a of the first stage of the DC power supply circuit. That is, the DC current clamp meter is clamped to the electric wire of the DC power supply circuit 15a of the first stage of the DC power supply circuit to adjust the zero point. Then, after adjusting the zero point of the DC current clamp meter 24, the forced grounding switch 27 of the forced grounding device 23 is turned on as shown in FIG. When a ground fault has occurred in the DC power supply circuit 15a due to the forced grounding switch 27 of the forced grounding device 23 being turned on, a DC exploration current can be supplied from the DC power supply device 11 to the DC power supply circuit 15a. However, since no ground fault has occurred in the DC power supply circuit 15a, the exploration current does not flow even if the forced grounding switch 27 of the forced grounding device 23 is turned on. Therefore, since the DC current clamp meter 24 does not detect the exploration current, it can be seen that no ground fault has occurred in the DC power supply circuit 15a.

Next, since no ground fault has occurred in the first-stage DC power supply circuit 15a, as shown in FIG. 3, a DC current clamp meter is clamped to the electric wire of the second-stage DC power supply circuit 15b in the next stage. And adjust the zero point. Then, after adjusting the zero point of the DC current clamp meter 24, the forced grounding switch 27 of the forced grounding device 23 is turned on as shown in FIG.

As shown in FIG. 4, since a ground fault has occurred in the second-stage DC power supply circuit 15b, when the forced grounding switch 27 of the forced grounding device 23 is turned on, the DC power supply panel is connected to the positive electrode of the DC power supply device 11. 13 switches 14bp, ground fault failure point F, forced grounding switch 27 of forced grounding device 23, limiting resistance 26 of forced grounding device 23, working terminal 25n of sound pole, and negative circuit of DC power supply device 11 are formed. Then, a DC exploration current flows. Since the exploration current is direct current, it does not flow in the ground capacitance Cbp of the electric wire of the direct current power supply circuit 15b.

In this state, the DC current clamp meter 24 operates the exploration current detection switch to detect the DC exploration current flowing through the wire of the clamped DC power supply circuit 15b. As described above, the limiting resistor 26 connected in series to the forced grounding switch 27 is a resistor that limits the magnitude of the exploration current to such a magnitude that the sequence circuit 16 does not malfunction. If there is no ground fault in the DC power supply circuit 15, exploration current will be supplied to the sequence circuit 16 of the DC power supply circuit 15, and the electrical equipment of the electric station will be operated in the sequence circuit 16. This is to avoid the possibility of malfunctioning the relay if it is connected to the ground.

In the state of FIG. 4, since the DC current clamp meter 24 detects the exploration current, it can be seen that a ground fault has occurred downstream of the DC power supply panel 13 of the DC power supply circuit 15b. Next, the AC current clamp meter 21 is clamped to the electric wire in front of the branch point of the branch circuit 17b of the DC power supply circuit 15b, and the probe current is detected by the DC current clamp meter 24. Since the DC current clamp meter 24 requires zero point adjustment for each measurement, the forced ground switch 27 of the forced grounding device 23 is turned off to adjust the zero point of the DC current clamp meter 24.

FIG. 5 is a circuit diagram showing a state in which the DC current clamp meter is moved to the electric wire in front of the branch point of the DC power supply circuit to adjust the zero point in the state of FIG. As shown in FIG. 5, the DC current clamp meter 24 is moved to the electric wire in front of the branch point of the branch circuit 17b of the DC power supply circuit 15b, which is the next measurement point, and the forced grounding switch 27 of the forced grounding device 23 is turned off. To. In this state, the zero point of the DC current clamp meter 24 is adjusted.

Then, in the state of FIG. 5, after adjusting the zero point of the DC current clamp meter 24, the forced grounding switch 27 of the forced grounding device 23 is turned on, and the DC exploration current from the DC power supply device 11 is supplied to the DC power supply circuit. Supply to 15b.

FIG. 6 is a circuit diagram showing a state in which the forced grounding switch of the forced grounding device is turned on and the exploration current is supplied after the zero point adjustment of the DC current clamp meter is performed in the state of FIG. As shown in FIG. 6, when the forced grounding switch 27 of the forced grounding device 23 is turned on, as in the case of FIG. 4, the switch 14bp of the DC power supply board 13 and the ground fault point F from the positive electrode of the DC power supply device 11 to the ground fault point F. A circuit is formed up to the forced grounding switch 27 of the forced grounding device 23, the limiting resistance 26 of the forced grounding device 23, the working terminal 25n of the sound pole, and the negative electrode of the DC power supply device 11, and a DC exploration current flows. Since the exploration current is direct current, it does not flow in the ground capacitance Cbp of the electric wire of the direct current power supply circuit 15b.

In this state, the DC current clamp meter 24 operates the exploration current detection switch to detect the DC exploration current flowing through the wire of the clamped DC power supply circuit 15b. The DC current clamp meter 24 is clamped before the branch point of the branch circuit 17b of the DC power supply circuit 15b and has passed the ground fault failure point F. Therefore, in the state of FIG. 6, the DC current clamp is performed. The meter 24 does not detect the exploration current. From this, there is a ground fault point F downstream of the electric wire near the DC bus 12, and there is no ground fault point F downstream of the electric wire before the branch point of the branch circuit 17b of the DC power supply circuit 15b. I understand. Therefore, it can be determined that there is a ground fault failure point F during this period.

According to the first embodiment, a forced grounding device for forcibly flowing a DC exploration current for exploring a ground fault point limited to a size that does not cause the sequence circuit to malfunction is provided, and a DC current clamp meter is provided. Since the exploration current is detected while adjusting the zero point using the above, it is possible to identify the ground fault failure point safely and with high sensitivity.

FIG. 7 is a block diagram of the forced grounding device according to the second embodiment of the present invention. FIG. 7A is a configuration diagram of a forced grounding device according to a first embodiment of the second embodiment of the present invention. In the first embodiment of the second embodiment, the ammeter 28 is connected in series with the forced grounding switch 27 of the forced grounding device 23 with respect to the first embodiment shown in FIG. The ammeter 28 measures and displays the current flowing through the forced grounding switch 27. Since the ammeter 28 displays the current flowing through the forced grounding switch 27, the ammeter 28 displays the total value of the exploration currents flowing through the plurality of DC power supply circuits 15.

According to the first embodiment, in addition to the effects of the first embodiment, by comparing the value of the probe current that appears in the DC current clamp meter 24, a direct current than the power supply circuit 15 in the probe by direct current clamp meter 24 It is possible to determine whether or not a ground fault has occurred. That is, the value of the exploration current displayed on the DC current clamp meter 24 measures the exploration current flowing through the DC power supply circuit 15, but the ammeter 28 measures the exploration current flowing through the plurality of DC power supply circuits 15. This is because the total value of is displayed.

FIG. 7B is a block diagram of the forced grounding device according to the second embodiment of the present invention. In the second embodiment of the second embodiment, the on / off control unit 29 for turning on / off the forced grounding switch 27 at a fixed cycle is provided with respect to the first embodiment shown in FIG. 7 (a). The on / off control unit 29 has a built-in timer and controls on / off by operating a timer that measures a certain period of time.

According to the second embodiment, in addition to the effect of the first embodiment, the forced grounding switch 27 is automatically turned on and off at regular intervals by the on / off control unit 29, so that the worker confirms the on / off of the forced grounding switch 27 and forced grounding. The zero point of the DC current clamp meter 24 can be adjusted when the switch 27 is off. Further, when the forced grounding switch 27 is on, the DC current clamp meter 24 can search for a ground fault point. Therefore, it is not necessary for the worker to turn on / off the forced grounding switch 27, and the amount of work is reduced. That is, one operator can perform the work of generating the exploration current by the forced grounding device 23 and the measurement by the DC current clamp meter 24.

FIG. 7C is a block diagram of the forced grounding device according to the third embodiment of the second embodiment of the present invention. In the third embodiment of the second embodiment, the notification unit 30 for notifying that the forced grounding switch 27 is on is provided for the second embodiment shown in FIG. 7 (b). The notification unit 30 is a buzzer that generates a sound when the forced grounding switch 27 is on, or an indicator lamp that lights up when the forced grounding switch 27 is on. According to the third embodiment, in addition to the effect of the second embodiment, the notification unit 30 notifies that the forced grounding switch 27 is on, so that the worker can easily grasp the on / off state of the forced grounding switch and workability. Is improved.

FIG. 7D is a configuration diagram of a forced grounding device according to a fourth embodiment of the second embodiment of the present invention. The fourth embodiment of the second embodiment is provided with an on / off control unit 29 that turns the forced grounding switch 27 on and off at regular intervals with respect to the first embodiment shown in FIG. The on / off control unit 29 is the same as that of the second embodiment. According to the fourth embodiment, in addition to the effect of the first embodiment shown in FIG. 3, the worker can adjust the zero point of the DC current clamp meter 24 when the forced grounding switch 27 is off, and the forced grounding switch 27 When it is on, the DC current clamp meter 24 can be used to search for a ground fault point, eliminating the need for workers to turn the forced grounding switch 27 on and off, reducing the amount of work. Further, the work of generating the exploration current by the forced grounding device 23 and the measurement by the DC current clamp meter 24 can be performed by one operator.

FIG. 7 (e) is a block diagram of the forced grounding device according to the fourth embodiment of the second embodiment of the present invention. In the fifth embodiment of the second embodiment, the notification unit 30 for notifying that the forced grounding switch 27 is on is provided for the fourth embodiment shown in FIG. 7 (d). The notification unit 30 is the same as that of the third embodiment. According to the fifth embodiment, in addition to the effect of the fourth embodiment, the notification unit 30 notifies that the forced grounding switch 27 is on, so that the worker can easily grasp the on / off state of the forced grounding switch and workability. Is improved.

The forced grounding device 23 of the first embodiment and the second embodiment described above and the DC current clamp meter 24 are combined to form a ground fault exploration device. This makes it possible to provide a ground fault exploration device having the effects of the first embodiment and the second embodiment.

In the above description, the DC current clamp meter 24 has described the case where the positive and negative electrodes of the DC power supply circuit 15 are collectively clamped, but if the load current is small and within the zero point adjustment range, the positive or negative electrode can be used. It may be clamped to the faulty electrode side in units of electric wires. Also in this case, the DC current clamp meter 24 is adjusted to the zero point in units of one electric wire. As a result, the influence of the ground capacitance can be canceled even when the length of the electric wire of the positive electrode or the negative electrode is different and the ground capacitance is different.

In the above description, the forced grounding device 23 is used for the work of the sound electrode of the work terminals of the positive electrode and the negative electrode for work at the connection point of the DC power supply circuit 15 where the ground fault has occurred to the DC bus 12. Although it is connected to the terminal 25n, it is also possible to connect to the voltage dividing middle point of the voltage dividing circuit 18 between the positive electrode and the negative electrode of the DC bus 12 instead of the working terminal of the sound electrode. In this case, since the voltage dividing midpoint of the voltage dividing circuit 18 is grounded by resistance, the limiting resistor 26 is unnecessary, but when the ground fault occurs in both the positive electrode and the negative electrode, the exploration current is the positive electrode and the negative electrode. Since it flows to both sides, the detection sensitivity decreases.

Next, the ground fault exploration method according to the third embodiment of the present invention will be described. 8 and 9 are flowcharts showing a ground fault fault search method according to a third embodiment of the present invention. The ground fault investigation method according to the third embodiment of the present invention is realized by using the forced grounding device 23 and the DC current clamp meter 24 of the first embodiment or the second embodiment. Further, a case where a ground fault occurs at the ground fault failure point F of the DC power supply circuit 15b of the electric station shown in FIG. 3 will be described as an example.

First, it is determined whether or not a ground fault has occurred in the DC power supply circuit (S1). Whether or not a ground fault has occurred in the DC power supply circuit is determined by the operation of the DC ground relay relay 19. In the case of a ground fault failure to the extent that the DC ground relay relay 19 does not operate, the voltage balance is periodically measured and determined from the tendency. Next, the faulty pole and the healthy pole of the DC power supply circuit in which the ground fault has occurred are determined (S2). The sound pole of the DC power supply circuit 15 is determined by the failure pole display of the DC ground relay. In the case of a ground fault failure to the extent that the DC ground relay relay 19 does not operate, it is determined by the measured value of the voltage balance.

When it is determined that a ground fault has occurred in the DC power supply circuit, the voltage dividing midpoint between the positive electrode and the negative electrode of the bus of the DC power supply circuit is ungrounded (S3). Making the voltage dividing midpoint of the voltage dividing circuit ungrounded prevents the exploration current from flowing to the voltage dividing midpoint of the voltage dividing circuit 18, which is a grounding point other than the ground fault point F, and detects the exploration current. This is to improve the accuracy.

When it is determined that a ground fault has occurred in the DC power supply circuit by measuring the voltage balance between the positive voltage and the negative voltage of the DC power supply circuit 15 or measuring the insulation resistance of the electric circuit of the DC power supply circuit 15. , The faulty pole and the healthy pole of the DC power supply circuit where the ground fault has occurred can be identified. On the other hand, when it is determined that a ground fault has occurred in the DC power supply circuit due to the operation of the DC ground relay, the faulty pole and the sound pole of the DC power supply circuit 15 in which the ground fault has occurred cannot be identified. , The sound pole of the DC power supply circuit 15 in which the ground fault has occurred is specified by measuring the voltage balance of the working terminals 25p and 25n of the working positive and negative electrodes at the connection point to the DC bus 12.

Then, the forced grounding device is connected to the sound pole of the DC power supply circuit in which the ground fault has occurred (S4). That is, the forced grounding device 23 is connected to the working terminal 25 of the healthy electrode among the working terminals 25p and 25n of the working positive electrode and the negative electrode at the connection point to the DC bus 12, and the DC exploration current from the DC power supply device 11 Is in a state where it can be supplied to the DC power supply circuit 15. In this state, the forced grounding switch 27 of the forced grounding device 23 is off.

Next, the DC current clamp meter is clamped to the electric wire of the DC power supply circuit in the vicinity of the DC bus, and the DC current clamp meter is adjusted to the zero point (S5). The zero point adjustment of the DC current clamp meter 24 is performed in a state where the forced grounding switch 27 of the forced grounding device 23 is turned off and the exploration current is not generated.

After adjusting the zero point of the DC current clamp meter 24, the forced grounding switch of the forced grounding device is turned on to generate an exploration current, and the exploration current can be detected by the DC current clamp meter (S6). By turning on the forced grounding switch 27 of the forced grounding device 23, the DC exploration current is supplied from the DC power supply device 11 to the DC power supply circuit 15b in which the ground fault has occurred, and the positive voltage of the DC power supply device 11 directs the DC. Circuits leading to the switch 14bp of the power supply panel 13, the ground fault failure point F, the forced grounding switch 27 of the forced grounding device 23, the limiting resistance 26 of the forced grounding device 23, the working terminal 25n of the sound pole, and the negative electrode of the DC power supply device 11. Is formed and a DC exploration current flows. No exploration current flows through the DC power supply circuit 15 in which no failure has occurred. Worker, DC current clamp meter 24 operates the probe current detection switch of the DC current clamp meter 24 so as to detect the probe current.

Then, it is determined whether or not the DC current clamp meter has detected the exploration current (S7). The DC current clamp meter 24 does not detect the exploration current when it is clamped to the DC supply circuit 15 where no failure has occurred. For example, as shown in FIG. 2, when the DC supply circuit 15a is clamped to a DC supply circuit 15a in which a failure has not occurred, the exploration current is not detected. When the DC current clamp meter 24 does not detect the probe current, the forced grounding switch is turned off and the DC current clamp meter is moved to the vicinity of the DC bus of another DC power supply circuit (S8). Then, the process returns to step S5. Normally, the search is performed sequentially from the DC power supply circuit 15a to the DC power supply circuit 15n, so another DC power supply circuit is the next-stage DC power supply circuit.

Therefore, the process of step S5 or less is performed for the DC circuit 15b in the next stage of the DC power supply circuit 15a. Since the DC power supply circuit 15b is a circuit including a ground fault failure point, the DC current clamp meter 24 detects the exploration current in step S7.

When the DC current clamp meter 24 detects the exploration current, it is determined that a ground fault has occurred on the downstream side of the DC current clamp meter through which the exploration current flows (S9). Then, as shown in FIG. 9, the forced grounding switch is turned off and the DC current clamp meter is moved to the branch point of the DC power supply circuit on the downstream side of the previous measurement point (S10). In this state, the DC current clamp meter is clamped to the electric wire of the DC power supply circuit, and the zero point of the DC current clamp meter is adjusted (S11). As a result, the zero point of the DC current clamp meter 24 is adjusted at the position where the DC current clamp meter 24 is moved without generating the exploration current.

After adjusting the zero point of the DC current clamp meter 24, the forced grounding switch of the forced grounding device is turned on to generate an exploration current, and the exploration current can be detected by the DC current clamp meter (S12).

Then, it is determined whether or not the DC current clamp meter has detected the exploration current (S13). When the DC current clamp meter detects the exploration current in the determination in step S13, it is determined that a ground fault has occurred on the downstream side of the DC current clamp meter through which the exploration current flows (S14), and the process returns to step S10. The process of step S10 or less will be performed.

If the DC current clamp meter does not detect the exploration current in the determination in step S13, a ground fault has occurred between the downstream side of the DC power supply circuit where the exploration current flows and the upstream side of the DC power supply circuit where the exploration current has stopped flowing. It is determined that it has occurred (S15).

For example, at the position of the branch point of the branch circuit 17b of the DC power supply circuit 15b including a ground fault point, since the ground fault point F is the upstream side of the DC power supply circuit 15b, a DC current clamp meter 24 exploration current Do not detect. Therefore, it is determined that a ground fault F has occurred between the vicinity of the DC bus 12 and the branch point of the branch circuit 17b of the DC power supply circuit 15b.

According to the third embodiment of the present invention, when a ground fault occurs in the DC power supply circuit 15b, the forced grounding device 23 is connected to the DC power supply circuit 15b where the ground fault has occurred, and the DC current clamp meter 24 has a DC current clamp meter 24. After adjusting the zero point, the DC current clamp meter 24 is used to search for a ground fault, and the presence or absence of the search current is repeatedly determined up to the branch point where the search current stops flowing, and the downstream side of the DC power supply circuit where the search current flows. Since it is determined that a ground fault has occurred between the and the upstream side of the DC power supply circuit where the search current has stopped flowing, the ground fault of the DC power supply circuit 15b can be searched safely, accurately, and efficiently. can.

Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

11 ... DC power supply, 12 ... DC bus, 13 ... DC power supply board, 14 ... Switch, 15 ... DC power supply circuit, 16 ... Sequence circuit, 17 ... Branch circuit, 18 ... Voltage division circuit, 19 ... DC ground fault Relay, 20 ... Low frequency AC power supply, 21 ... AC current clamp meter, 22 ... Flicker device, 23 ... Forced grounding device, 24 ... DC current clamp meter , 25 ... Working terminal, 2
6 ... Limiting resistance, 27 ... Forced ground switch, 28 ... Ammeter, 29 ... On / off control unit, 30 ... Notification unit

Claims (6)

When a ground fault occurs in any of the multiple DC power supply circuits that supply DC power from the DC power supply to the sequence circuit for operating the electrical equipment of the electric station, it is clamped to the electric wire of the DC power supply circuit. the DC current clamp meter zeroing is cracking line by detecting a probe current of the direct current supplied from the DC power supply device when probing the ground fault point, DC ground to detect the ground fault and fault electrode It is a forced grounding device used in a state where the midpoint of the voltage dividing circuit between the positive and negative sides of the DC bus of the DC power supply circuit to which the interlacing power supply is connected is ungrounded.
When the ground fault and the fault electrode are detected by the DC ground relay, it is connected to the work terminal of the sound pole among the positive and negative working terminals of the DC power supply circuit in which the ground fault has occurred. A limiting resistor that limits the magnitude of the exploration current to such an extent that the sequence circuit does not malfunction, and
It is connected in series with the limiting resistor and turned off when adjusting the zero point of the DC current clamp meter to make the limiting resistor ungrounded, and turned on when the DC current clamp meter searches for the ground fault point. A forced grounding device including a forced grounding switch for grounding the limiting resistor and supplying a DC exploration current from the DC power supply device to the DC power supply circuit. The forced grounding device according to claim 1, further comprising an ammeter connected in series to the forced grounding switch and measuring a current flowing through the forced grounding switch. The forced grounding device according to claim 1 or 2, further comprising an on / off control unit that turns the forced grounding switch on and off at regular intervals. The forced grounding device according to claim 3, further comprising a notification unit for notifying that the forced grounding switch is on. The forced grounding device according to any one of claims 1 to 4.
A ground fault detection device including a DC current clamp meter that detects a DC exploration current supplied from the DC power supply device after being clamped to the electric wire of the DC power supply circuit and adjusting the zero point. .. When a ground fault or a faulty electrode is detected by a DC ground relay in any of a plurality of DC power supply circuits that supply DC power to a sequence circuit for operating electrical equipment in an electric station. Based on the operation content, the faulty pole and the healthy pole of the DC power supply circuit where the ground fault has occurred are determined.
The voltage dividing midpoint of the voltage dividing circuit between the positive electrode and the negative electrode of the DC bus of the DC power supply circuit to which the DC ground relay is connected is set as ungrounded.
Of the positive and negative sides of the DC power supply circuit, the working terminal of the DC bus of the healthy pole passes from the positive side of the DC power supply device to the ground fault point and the working terminal of the healthy pole to reach the negative side of the DC power supply device. A circuit is formed to generate a DC exploration current, and a forced grounding device for flowing it to the DC power supply circuit is connected.
With the forced grounding switch of the forced grounding device turned off and the exploration current not being generated, the DC current clamp meter is clamped to the electric wire of the DC power supply circuit near the DC bus, and the DC current clamp meter is adjusted to the zero point. ,
After the zero point adjustment, the forced grounding switch of the forced grounding device is turned on to generate the exploration current and enable the detection of the exploration current by the DC current clamp meter.
When the DC current clamp meter does not detect the exploration current, the DC current clamp meter is sequentially moved to the vicinity of the DC bus of another DC power supply circuit among the plurality of DC power supply circuits to sequentially move the exploration current. Repeatedly determine the presence or absence of the exploration current up to the point where
When the DC current clamp meter detects the exploration current, the DC current clamp meter is sequentially moved to the branch point of the DC power supply circuit on the downstream side and repeated until the branch point where the exploration current stops flowing. Judge the presence or absence of
It is characterized in that it is determined that the ground fault has occurred between the downstream side of the DC power supply circuit through which the exploration current flows and the upstream side of the DC power supply circuit in which the exploration current has stopped flowing. How to search for ground faults.

Images