JP7675411B2 - Power System - Google Patents

Description

The present invention relates to a power system having a power generation unit, a conversion unit, a transformer, and a grid connection unit.

2. Description of the Related Art Conventionally, there has been known a system for remotely controlling a power conditioner used in a power generation system including a power conditioner that enables electric power generated by a power generation source to be connected to a commercial grid (see Patent Document 1).
This system comprises a monitoring device that monitors the status of the power generation system, a remote operation auxiliary device connected to the monitoring device and the power conditioner in a manner that allows sequence control, a control means connected to the monitoring device and controlling the status of the power conditioner, and a first detection unit that is disposed in the power conditioner and is capable of detecting a first abnormality on the commercial grid side, and the control means transmits an operation signal that is different from the abnormality detection signal of the first abnormality to the first detection unit via the monitoring device and the remote operation auxiliary device, and by sequence control, there are cases in which the power conditioner is changed from an operating state to a stopped state, and cases in which the power conditioner is changed from a stopped state to an operating state.

JP 2020-182259 A

However, in the system described in Patent Document 1, the first abnormality is an earth fault overvoltage, and the first detection unit is capable of receiving the abnormality detection signal from the earth fault overvoltage relay. However, in an actual system (grid), power outages can occur in addition to earth faults. Therefore, when an earth fault and power outage occur, the power supply to the earth fault overvoltage relay is also stopped at the same time, and there is a problem that the abnormality detection signal cannot be output from the earth fault overvoltage relay.

In consideration of these points, the present invention aims to provide a power system that can achieve "detection of an earth fault overvoltage state during a power outage" by providing a capacitor device that supplies power from a power source to an earth fault overvoltage relay unit during a power outage.

The power system 1 according to the present invention is a power system having a power generation unit 2, a conversion unit 3 that converts a DC current or an AC current from the power generation unit 2 into a low-voltage AC current L, a transformer 4 that transforms the low-voltage AC current L from the conversion unit 3 into a higher voltage AC current H, and a system connection unit 5 that connects the transformer 4 to a system K. The system connection unit 5 is connected to a high-voltage circuit 6H that connects between the transformer 4 and the system K and passes a high-voltage AC current H, a zero-phase sequence voltage detector 7 provided in the high-voltage circuit 6H, and a zero-phase sequence output circuit 6Z that passes a zero-phase sequence output current Z from the zero-phase sequence voltage detector 7 and detects an earth fault overvoltage state based on the zero-phase sequence output current Z. a capacitor device 9 connected to a capacitor output circuit 6D that supplies power from a power source to the earth fault overvoltage relay unit 8 during a power outage , the system connection unit 5 having a voltage transformer 10 that is provided in the high voltage circuit 6H and that transforms a high voltage AC current H flowing through the high voltage circuit 6H into a lower voltage transformed output current S, and the capacitor device 9 is charged with electricity from the voltage transformer 10 via a capacitor input circuit 6D' that branches off from a transformer output circuit 6S that carries the transformed output current S from the voltage transformer 10 .

A second feature of the power system 1 according to the present invention is, in addition to the first feature, that the system connection unit 5 includes a sensor current transformer 11 that is provided in the high- voltage circuit 6H and outputs a sensor output current B of a smaller current from the high-voltage AC current H flowing in the high-voltage circuit 6H, a transformer output electric circuit 6S that flows a transformer output current S from the instrument transformer 10, and a sensor output electric circuit 6B that flows a sensor output current B from the sensor current transformer 11, and the transformer output current S and the sensor output electric circuit 6B are connected to the transformer output electric circuit 6S and the sensor output electric circuit 6B. The current transformer output circuit 6R for transmitting the transformed output current R from the instrument current transformer 11a is a single-phase two-wire circuit, and the sensor current transformer 11 is provided for each of the two wires of the single-phase two-wire current transformer output circuit 6R.

A third feature of the power system 1 according to the present invention is that when the reverse power relay unit 12 in the power system according to the second feature detects a reverse power generation state, the reverse power relay unit 12 stops the conversion of the conversion unit 3 (excluding the disconnection of the conversion unit (3)) via a signal to the conversion unit 3.
In addition, when the earth fault overvoltage relay unit 8 in the power system of the first feature detects an earth fault overvoltage condition, the power system 1 may stop the conversion of the conversion unit 3 via a signal to the conversion unit 3.

A fourth feature of the power system 1 of the present invention is, in addition to the second feature described above, that the earth fault overvoltage relay unit 8, the reverse power relay unit 12, and a calculation unit 13 that calculates at least the power in the high-voltage circuit 6H based on the transformer output current S and the sensor output current B are provided within a single device housing 14 , the reverse power relay unit 12 and the instrument transformer 10 are connected via the calculation unit 13, and the reverse power relay unit 12 and the sensor current transformer 11 are also connected via the calculation unit 13 .

Due to these features, by having a capacitor device 9 that supplies power from the power source during a power outage to the earth fault overvoltage relay unit 8, which detects an earth fault overvoltage state based on the zero-phase output current Z from the zero-phase voltage detector 7, unlike Patent Document 1, even if a power outage occurs along with an earth fault, the power supply to the earth fault overvoltage relay unit 8 does not stop and a signal can be output from the earth fault overvoltage relay unit, making it possible to detect an earth fault overvoltage state even during a power outage.

In addition, by having a reverse power relay unit 12 that detects a reverse power generation state based on the transformer output current S from the instrument transformer 10 and the sensor output current B from the sensor current transformer 11, it is possible to prevent or reduce the backflow of the power generated by the power generation unit 2 to the system K via the conversion unit 3, the transformer 4, and the system connection unit 5.

Furthermore, when the earth fault overvoltage relay unit 8 detects an earth fault overvoltage state or when the reverse power relay unit 12 detects a reverse power generation state, the conversion of the conversion unit 3 is stopped via a signal to the conversion unit 3, thereby preventing the power generated by the power generation unit 2 via the conversion unit 3 from flowing back to the grid K. In addition, when the conversion of the conversion unit 3 is stopped, it is not necessary to match the output from the conversion unit 3 to the voltage and phase of the grid K when the conversion is resumed. This means that the power system 1 can be restored in a shorter time and with less effort than if any part of the electrical path from the conversion unit 3 to the grid K is interrupted.

Furthermore, by arranging the earth fault overvoltage relay unit 8, the reverse power relay unit 12, and the calculation unit 13 that calculates the power of the high-voltage circuit 6H, etc., within a single device housing 14, "space saving" is achieved by the amount of space provided within the single device housing 14, and sufficient space can be secured for installing other equipment.
Additionally, when the relay unit and calculation unit are separate devices, the minute errors that occur in each unit are different, so that malfunctions such as the relay unit detecting a reverse power generation state on its own will not occur, and malfunctions can be reduced.

The power system of the present invention can achieve things like "detection of an earth fault overvoltage state during a power outage" by providing a capacitor device that supplies power from a power source to the earth fault overvoltage relay unit during a power outage.

1 is a schematic diagram showing a power system according to the present invention;

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
<Overall configuration of power system 1>
As shown in FIG. 1, the power system 1 according to the present invention has a power generation unit 2, a conversion unit 3, a transformer 4, and a system connection unit 5, which are described below. The system connection unit 5 has a high-voltage circuit 6H, a zero-phase-sequence voltage detector 7, a zero-phase-sequence output circuit 6Z, an earth fault overvoltage relay unit 8, a capacitor output circuit 6D, and a capacitor device 9, which are described below.
The power system 1 may include, within the system connection unit 5, an instrument transformer 10, a sensor current transformer 11, a transformer output electric circuit 6S, a sensor output electric circuit 6B, and a reverse power relay unit 12, which will be described later.
The power system 1 may include a calculation unit 13 and an equipment housing 14 (described later) in the grid connection unit 5 .

Furthermore, the power system 1 may include a power breaker 21, loads 22 (power loads 22a and lighting loads 22b), a load transformer 23, and a load breaker 24, which will be described later.
In addition, the power system 1 may have a voltage and current transformer (VCT) 31a in the electric circuit (high voltage circuit 6H) between the system connection unit 5 and the system K, and may also have a power purchase watt-hour meter, a power selling watt-hour meter, pole air switches (PAS), a protective relay device (Storage Over Current Ground (SOG)) attached to the pole air switches, etc., which are not shown. In addition, the pole air switches may have a separate built-in voltage transformer, a zero-phase voltage detector, and a lightning arrester.
The trading transformer 31a, the power purchase watt-hour meter, the power sale watt-hour meter, the pole-mounted air switch, and the protective relay device may be included in the system on the system K side (the electric power company side) described later.

Here, the current, voltage, power, and capacity in the present invention may be values within a rated range, and in this case, they can be called rated current, rated voltage, rated power, and rated capacity. These rated currents, etc. can also be said to be limit values of current, etc. guaranteed by manufacturers for the safe use of electrical products, and further, ratings can be said to be usage limits or conditions for devices or equipment that guarantee safe and proper operation.
When the current in the present invention is an alternating current, the current value (current value), voltage value (voltage value), power value (power value), and capacitance value (capacity value) may be effective values.
In addition, the "electrical circuit" in the present invention is something that carries electricity (current), and includes conductors such as copper, aluminum, silver, gold, and nichrome, cables in which such conductors are covered with insulation, and general electric wires.

<Power generation section 2>
As shown in FIG. 1, the power generation unit 2 is the part that generates electricity and may have any configuration, such as solar power generation, wind power generation, hydroelectric power generation, geothermal power generation, solar thermal power generation, power generation using heat in the atmosphere or other heat present in nature, or power generation using biomass (organic matter derived from plants and animals that can be used as an energy source).
In addition, the power generating unit 2 may generate power by utilizing ocean temperature difference, wave power, tidal currents (ocean currents), or tides.

The number of power generation units 2 in one power system 1 is not particularly limited, and may be, for example, one or more.
The power generation capacity (capacity) of the power generation unit 2 is not particularly limited, and may be, for example, 100 kW or more and 30,000 kW or less, preferably 300 kW or more and 20,000 kW or less, and more preferably 500 kW or more and 10,000 kW or less.
The following will particularly describe the solar power generation unit 2 that generates solar power.

The solar power generation unit 2 includes a solar cell 2a.
In addition, the solar power generation unit 2 may include an actinometer that measures solar radiation intensity, and a current collector that collects DC current from the solar cells 2a, a connection box, etc., and sends it to the conversion unit 3 described later.
The solar cell 2a in the solar power generation unit 2 may be multiple, and the multiple solar cells 2a may be connected in series to form a solar cell string.
The solar power generation unit 2 may have a junction box in which a plurality of solar cell strings are connected in parallel, and there may be a plurality of such junction boxes.

<Solar cell 2a>
As shown in Fig. 1, each solar cell 2a generates DC power between the positive and negative poles when exposed to light. The solar cell 2a is usually in the form of a panel, and the amount of power generated varies depending on the angle at which it is installed.
The solar cell 2a may be installed at a predetermined angle relative to the installation location via a stand (not shown) or the like. In this case, the area underneath the stand may be used as a grass growing area or a cultivated land for agricultural crops.
Furthermore, among the multiple solar cells 2a, the positive pole of one solar cell 2a is connected to the negative pole of another solar cell 2a, and the positive pole of another solar cell 2a is connected to the negative pole of yet another solar cell 2a, and this process is repeated to connect the multiple solar cells 2a in series to form a solar cell string.

In this way, the voltage between the + and - poles of the entire solar cell string in which multiple solar cells 2a are connected in series is the sum of the DC voltages generated by each solar cell 2a, and varies depending on the weather, time, etc. The power output from the power output terminal of the solar cell string is the sum of the power of each solar cell 2a, and may be 500 W or more and 6000 W or less.
The above-mentioned multiple solar cell strings are connected in parallel to one junction box, so that the voltage between the positive and negative poles of each solar cell string is the same.
However, currents from a plurality of solar cell strings may flow into one junction box, and the power collected in the junction box may be 2.5 kW or more and 90 kW or less.

<Conversion unit 3>
As shown in FIG. 1, the conversion unit 3 is a part that converts the DC current or AC current from the power generation unit 2 described above into a low-voltage AC current L.
The conversion unit 3 may be equipped with an inverter that converts the direct current from the solar cell 2a into alternating current, and may also be equipped with a controller that controls the voltage and frequency of the alternating current converted by the inverter, an air circuit breaker (ACB), etc.
The conversion unit 3 is also called a power conditioner (PAWCON).
The number of conversion units 3 in one power system 1 is not particularly limited, and may be, for example, multiple (for example, four or five) or just one.

The conversion power (capacity) that the conversion unit 3 can convert is not particularly limited, but may be, for example, 30 kW or more and 10,000 kW or less, preferably 50 kW or more and 5,000 kW or less, and more preferably 100 kW or more and 2,000 kW or less (250 kW, 500 kW, etc.).
Furthermore, the conversion power of the conversion unit 3 may be smaller than the power generation power of the above-mentioned solar power generation unit 2 (in other words, the power generation power may be greater than the conversion power), and in this case, the solar cell 2a can be said to be overloaded with respect to the conversion unit 3.
In addition, the conversion unit 3 may have an undervoltage relay (UVR), an overvoltage relay (OVR), an underfrequency relay (UFR), an overfrequency relay (OFR), or a passive or active islanding protection device.

<Transformer 4>
1, the transformer 4 is a device that transforms (boosts) the low voltage AC L from the conversion unit 3 to a higher voltage AC H, and is a so-called transformer. Note that "transformer" is an abbreviation for "transformer." Note that the transformer 4 can also be called a power generation transformer because it transforms the current from the power generation unit 2 via the conversion unit 3.
The number of transformers 4 in one power system 1 is not particularly limited, and may be, for example, multiple (e.g., two) or one.
In addition, it can also be said that the transformer 4 is connected between the system K (high voltage line 6H side) and the conversion unit 3 (low voltage line 6L side) in the power system 1 described later.
The capacity of the transformer 4 (unit: VA, continuous rating) is not particularly limited, and may be, for example, 50 kVA or more and 2000 kVA or less, preferably 100 kVA or more and 1500 kVA or less, and more preferably 200 kVA or more and 1000 kVA or less (300 kVA, 500 kVA, etc.).

The configuration of the transformer 4 is not limited, and it may be, for example, a two-winding transformer, a three-winding transformer, or a transformer with four or more windings.
Hereinafter, transformer 4 will be primarily described as being a two-winding transformer.
The transformer 4, which is a two-winding transformer, may have, for example, a primary side on the high-voltage circuit 6H side and a secondary side on the low-voltage circuit 6L side. In this case, there are no particular restrictions on the specific values, but for example, the voltage of the primary side, which is the high-voltage circuit 6H side, may be 5,000 V or more and 40,000 V or less, preferably 5,500 V or more and 30,000 V or less, and more preferably 6,000 V or more and 25,000 V or less (6,600 V or 22,000 V, etc.), and the voltage of the secondary side, which is the low-voltage circuit 6L side, may be 10 V or more and 1,000 V or less, preferably 50 V or more and 800 V or less, and more preferably 100 V or more and 600 V or less (210 V, 105 V to 210 V, etc.).

There are no particular restrictions on the wiring method of the primary and secondary sides of the transformer 4, but for example, the primary side on the high-voltage circuit 6H side may be star-connected (Y-connected) and the secondary side on the low-voltage circuit 6L side may be triangular-connected (Δ-connected) (i.e., Y-Δ connection), or the order of the primary side and secondary side may be Y-Y connection, Δ-Y connection, or Δ-Δ connection.
Transformer 4 may be an oil-filled transformer (self-cooled, air-cooled, water-cooled, etc.) or a dry-type transformer (self-cooled, air-cooled, water-cooled, etc.), and may also be equipped with a contact prevention plate or be class B grounded.

<System connection unit 5>
As shown in FIG. 1, the system connection unit 5 is a portion that connects the above-mentioned transformer 4 to the system K.
As described above, the system connection unit 5 has a high-voltage circuit 6H, which will be described later, a zero-phase voltage detector 7, a zero-phase output circuit 6Z, an earth fault overvoltage relay unit 8, a capacitor output circuit 6D, a capacitor device 9, etc.
As described above, the system connection unit 5 may have an instrument transformer 10, a sensor current transformer 11, a transformer output circuit 6S, a sensor output circuit 6B, and a reverse power relay unit 12, as described below, and may also have a calculation unit 13 and an equipment housing 14, as described below.
The system connection unit 5 may include a vacuum circuit breaker 5a, a disconnector 5b, and a load switch 5c, which will be described later, and may also include an overcurrent relay 5d and an instrument current transformer 11a, which will be described later.

<Vacuum circuit breaker 5a, disconnector 5b, load switch 5c, overcurrent relay 5d>
As shown in FIG. 1, a vacuum circuit breaker (VCB) 5a is provided in a high-voltage circuit 6H (described later), and is a device that opens and closes (three-phase, three-wire collectively) the high-voltage circuit 6H in a state in which a high-voltage AC current H (load current) is flowing, and extinguishes the arc in the vacuum valve.
The vacuum circuit breaker 5a may be provided, for example, between a voltage transformer 10 (a branch point of the transformer branch electric circuit 6S') and the sensor current transformer 11 (or the instrument current transformer 11a), which will be described later. The vacuum circuit breaker 5a may be of an electric spring operation (capacitor trip) type.
As shown in Fig. 1, the disconnecting switch (DS) 5b is provided in the high-voltage circuit 6H described later, and is a device that opens and closes the high-voltage circuit 6H when high-voltage AC current H (load current) is not flowing. The disconnecting switch 5b does not have a function of cutting off current, and the disconnecting switch 5b is opened and closed after cutting off the current with another circuit breaker. The disconnecting switch 5b may be provided, for example, between the instrument transformer 10 (branch point of the transformer branch circuit 6S') and the system K (or the commodity transformer 31a). The disconnecting switch 5b may also be opened and closed by a hook operation.

As shown in FIG. 1, the load break switch (LBS) 5c may be provided in the high-voltage circuit 6H described later, and is a device that opens and closes the high-voltage circuit 6H (three-phase three-wire collectively) in a state in which a high-voltage AC current H (load current) flows, and is also called a high-voltage AC load break switch. The load break switch 5c may have power fuses (four or the like). The load break switch 5c may also be equipped with an insulating barrier, and the load break switch 5c may be opened and closed by a hook operation. The number of load break switches 5c in one power system 1 is not particularly limited, and may be, for example, multiple (for example, two or the like) or one, or may be the same number as the number of transformers (the number of the above-mentioned transformer (power generation transformer) 4 and the load transformer 23 described later). Hereinafter, the number of load break switches 5c will be mainly described as two. The two load switches 5c may be provided, for example, in the high-voltage circuit 6H branching off between the sensor current transformer 11 (or the instrument current transformer 11a) and each transformer (the generating transformer 4, the load transformer 23).
As shown in FIG. 1, when the system connection unit 5 has the current transformer 11a, the overcurrent relay (OCR) 5d is connected to the current transformer 11a via a transformer output circuit 6R described later, receives the transformer output current R (lower voltage transformer output current R corresponding to the low voltage AC current L flowing in the high voltage circuit 6H) output from the current transformer 11a, and performs a predetermined operation (for example, outputs a stop signal to stop the conversion of the above-mentioned conversion unit 3) when the transformer output current R exceeds a certain value (value of operating current) for a certain time (for example, about 1 second of operating time). In one power system 1, the number of overcurrent relays 5d and the number of the above-mentioned current transformers 11a are the same, and the number may be one or more. The power source of the overcurrent relay 5d is connected to an uninterruptible power supply (not shown) or the like and is input from the uninterruptible power supply or the like.

<High voltage circuit 6H, low voltage circuit 6L>
As shown in Fig. 1, the high-voltage circuit 6H is an electric circuit that connects the above-mentioned transformer 4 and the system K and passes high-voltage AC current H, and can also be considered as a high-voltage cable. The high-voltage circuit 6H may branch midway (for example, between the sensor current transformer 11 (or the instrument current transformer 11a) and the transformer 4) to the transformer 4 and a load transformer 23 described later, and these branched electric circuits also pass high-voltage AC current H, so they can also be considered as high-voltage circuit 6H. The high-voltage circuit 6H may be a set of three in the case of three-phase three-wire (3φ3W) or single-phase three-wire (1φ3W) or a set of two in the case of single-phase two-wire (1φ2W), and may be a set of multiple lines depending on the power distribution system (power transmission system).
1, the low-voltage circuit 6L is an electric circuit that connects the above-mentioned conversion unit 3 and the transformer 4 and passes the low-voltage AC current L, and can also be considered as a low-voltage cable. The low-voltage circuit 6L may also be branched to each of the conversion units 3 in the middle (for example, between the transformer 4 and the conversion unit 3) depending on the number of conversion units 3, and these branched electric circuits also pass the low-voltage AC current L, so they can also be considered as low-voltage circuit 6L. In addition, the electric circuit between the transformer 4 and a load 22 (power load 22a) described later and the electric circuit between a load transformer 23 described later and a load 22 (lighting load 22b) also pass the low-voltage AC current L, so they can also be considered as low-voltage circuit 6L. The low-voltage circuit 6L may also be configured in a set of three cables if it is three-phase three-wire (3φ3W) or single-phase three-wire (1φ3W), etc., or in a set of two cables if it is single-phase two-wire (1φ2W), etc., so multiple cables may be configured in a set depending on the power distribution method (power transmission method).

<Zero-phase voltage detector 7, etc.>
1, the zero-phase potential device (ZPD) 7 is provided in the high-voltage circuit 6H described above, and is a device for detecting whether or not a zero-phase voltage has occurred on the high-voltage circuit 6H side due to an earth fault (such as a complete one-line earth fault in a three-phase three-wire system) occurring anywhere in the system (including the system K side) such as the high-voltage circuit 6H side in the power system 1. The zero-phase voltage detector 7 is also called a zero-phase voltage transformer (ZVT), etc.
The electric circuit between the zero-phase voltage detector 7 and the earth fault overvoltage relay unit 8 described later is a zero-phase output electric circuit 6Z, and the zero-phase output electric circuit 6Z may be a set of three wires in the case of a three-phase three-wire (3φ3W) system, etc., or may be a set of multiple wires depending on the power distribution method (power transmission method).
In the zero-phase output circuit 6Z, when the zero-phase voltage detector 7 detects a zero-phase voltage, a zero-phase output current Z of a lower voltage (e.g., approximately 1 V, approximately 6 to 9 V, etc.) corresponding to the zero-phase voltage generated in the power system 1, etc. is output from the zero-phase voltage detector 7 and flows through the zero-phase output circuit 6Z.
In addition, the zero-phase voltage detector 7 may incorporate a capacitor for voltage division, or may be an A-type ground.

In addition, "the zero-phase voltage detector 7 is provided in the high-voltage circuit 6H" means that the zero-phase voltage detector 7 is connected to a zero-phase branch circuit 6Z' branching off from the high-voltage circuit 6H, and this zero-phase branch circuit 6Z' may be a set of three cables if it is a three-phase three-wire (3φ3W) circuit, etc., and may be a set of multiple cables depending on the power distribution method (power transmission method).
The zero-phase branch electric circuit 6Z' may branch off from anywhere in the high-voltage circuit 6H, for example, it may branch off from between the load switch 5c and the transformer 4 in the high-voltage circuit 6H.

<Earth fault overvoltage relay unit 8>
As shown in FIG. 1, the earth fault overvoltage relay unit 8 is connected to the zero-phase voltage detector 7 via the above-mentioned zero-phase output circuit 6Z, and detects an earth fault overvoltage state based on the zero-phase output current Z. When this earth fault overvoltage relay unit 8 detects an earth fault overvoltage state, it may output a signal to stop the conversion of the above-mentioned conversion unit 3, for example.
Here, "detecting an earth fault overvoltage state" means, as described above, that an earth fault occurs somewhere in the power system 1, etc., causing a zero-phase voltage to occur on the high-voltage circuit 6H side, and the zero-phase output current Z (a lower voltage zero-phase output current Z corresponding to the zero-phase voltage generated on the high-voltage circuit 6H side, etc.) output from the zero-phase voltage detector 7 is input to the earth fault overvoltage relay unit 8, and the zero-phase output current Z becomes equal to or greater than a predetermined value (threshold value).
Furthermore, "the zero-phase output current Z becomes greater than or equal to a predetermined value" does not necessarily mean that the zero-phase output current Z becomes greater than or equal to a threshold value strictly, but depending on the resolution and settings of the earth fault overvoltage relay unit 8, it may also mean that the zero-phase output current Z "becomes greater than or equal to a value that can be regarded as the threshold value", and the "value that can be regarded as the threshold value" may depend on the resolution of the earth fault overvoltage relay unit 8, and may be, for example, the sum of the threshold value and 1 mA, 1 μA, 1 nA, etc.
Incidentally, this includes not only the case where a signal is output to the conversion unit 3 immediately after the zero-phase output current Z becomes equal to or greater than a predetermined value (threshold value), but also the case where a signal is output after a predetermined time has elapsed.
Here, the "predetermined time" may be 0.1 seconds or more and 15.0 seconds or less, 0.3 seconds or more and 5.0 seconds or less, 0.5 seconds or more, or 2.0 seconds or more after the zero-phase output current Z becomes equal to or greater than a predetermined value.

The output signal from the earth fault overvoltage relay unit 8 may be directly input to the conversion unit 3, or may be input to a control device (not shown) of the conversion unit 3 (described later) or the calculation unit 13. When the output signal from the earth fault overvoltage relay unit 8 is directly input to the conversion unit 3, the earth fault overvoltage relay unit 8 can also be said to be a control device.
In one power system 1, the number of earth fault overvoltage relay units 8 is the same as the number of the zero-phase sequence voltage detectors 7 described above, and the number may be one or more.
The power source of the earth fault overvoltage relay unit 8 is connected to a capacitor device 9 (described later), an instrument transformer 10, and other uninterruptible power supplies (not shown), and is input from the capacitor device 9, etc.
The ground fault overvoltage relay unit 8 can also be said to be an overvoltage ground relay (OVGR).

<Capacitor device 9>
1, the capacitor device 9 is a device that charges and discharges electricity (electrical energy), and is connected to the above-mentioned earth fault overvoltage relay unit 8 by a capacitor output electric circuit 6D that supplies power source power (control power source) to the earth fault overvoltage relay unit 8. The capacitor device 9 can also be called a capacitor device.
When the power system 1 and the like are not experiencing a power outage (non-power outage), the capacitor device 9 is charged with electricity from the potential transformer 10 via a capacitor input circuit 6D' branching off from a transformer output circuit 6S through which a transformer output current S from the potential transformer 10 described below flows. If the transformer output circuit 6S is a three-phase three-wire circuit, the current may be input to the capacitor device 9 as a single-phase two-wire capacitor input circuit 6D' via a voltmeter changeover switch (not shown).
In the event of a power outage, the capacitor device 9 discharges the electricity that was stored therein, causing a capacitor output current D (140 V, 154 V, etc.) to flow through the capacitor output circuit 6D, thereby supplying power from the power source to the earth fault overvoltage relay unit 8.
As a result, the capacitor device 9 supplies power source power to the earth fault overvoltage relay unit 8 via the capacitor output circuit 6D when a power outage occurs in a system (including the system K side) such as the high-voltage circuit 6H side in the power system 1.

The capacitor device 9 may have a charging indicator lamp that lights up when the capacitor device 9 is charged (fully charged), and a discharge switch (e.g., a configuration in which the switch is pressed and held until the charging indicator lamp mentioned above goes out) that is used to forcibly discharge the capacitor device 9 when installing or removing the capacitor device 9.
The capacitor device 9 has a capacitor as an electrical component that charges and discharges electricity, and may also have a fuse (φ5.2×20 mm, 5 A, etc.) provided in the circuit immediately after the transformer output current S is input via the capacitor input circuit 6D', a rectifier that rectifies the transformer output current S, which is AC and input via the capacitor input circuit 6D', to DC, a surge absorber provided before and/or after the rectifier, a charging current limiting resistor provided in the circuit that charges the capacitor with the rectified DC, a discharge resistor provided in the circuit that discharges when the above-mentioned discharge switch is pressed, a lamp current limiting resistor for the above-mentioned charge indicator lamp, and a diode provided in the circuit that discharges in the event of a power outage.
The input voltage of the capacitor device 9 is 10V or more and 500V or less, preferably 40V or more and 400V or less, and more preferably 80V or more and 300V or less (100V, 110V, 200V, 220V, etc.), the charging voltage (which can also be said to be the voltage of the capacitor output current D to be discharged) is 10V or more and 600V or less, preferably 50V or more and 500V or less, and more preferably 100V or more and 400V or less (140V, 154V, 280V, 308V, etc.), and the consumption current (which can also be said to be the current of the capacitor output current D to be discharged) is 1mA or more and 100mA or less, preferably 3mA or more and 70mA or less, and more preferably 5mA or more and 40mA or less. (e.g., 8 mA or 20 mA), the capacitor capacity (capacity of the capacitor as an electronic component) is 100 μF or more and 5000 μF or less, preferably 200 μF or more and 4000 μF or less, more preferably 300 μF or more and 3000 μF or less (e.g., 470 μF or 1500 μF), the charging time is 0.01 seconds or more and 0.50 seconds or less, preferably 0.05 seconds or more and 0.40 seconds or less, more preferably 0.10 seconds or more and 0.30 seconds or less (e.g., within 0.2 seconds), and the discharge time may be 0.1 seconds or more and 30.0 seconds or less, preferably 0.5 seconds or more and 20.0 seconds or less, more preferably 1.0 seconds or more and 10.0 seconds or less (about 3 seconds, about 6 to 7 seconds, etc.). Note that this discharge time may be longer (or two or more times or more longer) than the predetermined time in the above-mentioned earth fault overvoltage relay unit 8 or the predetermined time in the reverse power relay unit 12 described later.

<Instrument transformer 10, etc.>
1, a voltage transformer (VT) 10 is provided in the high-voltage circuit 6H described above, and is a device that transforms (steps down) the high-voltage AC current H flowing through the high-voltage circuit 6H into a lower-voltage transformed output current S. Note that not only one voltage transformer 10 but also multiple (e.g., two) voltage transformers 10 may be present in one power system 1.
The electric path between the potential transformer 10 and the reverse power relay unit 12 (or the calculation unit 13) described later is a transformer output electric path 6S through which the transformer output current S flows, and the transformer output electric path 6S may be a set of three electric paths in the case of a three-phase three-wire (3φ3W) system or the like, or may be a set of multiple electric paths depending on the power distribution system (power transmission system). Note that when the transformer output electric path 6S is a three-phase three-wire system, as described above, it may be input to the reverse power relay unit 12 or the like as a single-phase two-wire system via a voltmeter changeover switch (not shown).
The transformer output circuit 6S is configured such that (at least a portion of) the transformer output current S of a lower voltage (e.g., 110 V) corresponding to the voltage of the high-voltage AC current H flowing through the high-voltage circuit 6H is output from the instrument transformer 10 and flows through the transformer output circuit 6S.

The capacity of the potential transformer 10 is not particularly limited, and may be, for example, 10 VA or more and 500 VA or less, preferably 20 VA or more and 300 VA or less, and more preferably 40 VA or more and 200 VA or less (e.g., 100 VA).
The potential transformer 10 is not limited in its configuration and may be a transformer with three or more windings, but will be described primarily as a two-winding transformer.
The instrument transformer 10, which is a two-winding transformer, may have, for example, a primary side on the high-voltage circuit 6H side and a secondary side on the reverse power relay unit 12 or the like side. In this case, there are no particular restrictions on the specific values, but for example, the voltage of the primary side, which is the high-voltage circuit 6H side, may be 5,000 V or more and 40,000 V or less, preferably 5,500 V or more and 30,000 V or less, and more preferably 6,000 V or more and 25,000 V or less (6,600 V or 22,000 V, for example), and the voltage of the secondary side, which is the reverse power relay unit 12 side, may be 10 V or more and 600 V or less, preferably 20 V or more and 400 V or less, and more preferably 50 V or more and 300 V or less (110 V, for example).
The potential transformer 10 may have a power fuse (PF) on the primary side and/or the secondary side.

In addition, "the voltage transformer 10 is provided in the high-voltage circuit 6H" means that the voltage transformer 10 is connected to a transformer branch circuit 6S' branching off from the high-voltage circuit 6H, and this transformer branch circuit 6S' may be a set of three cables if it is a three-phase three-wire (3φ3W) circuit, etc., and may be a set of multiple cables depending on the distribution method (transmission method).
The transformer branch electric circuit 6S' may branch off from anywhere in the high-voltage power line 6H, for example, it may branch off from between the vacuum circuit breaker 5a and the disconnecting switch 5b in the high-voltage power line 6H.

<Sensor current transformer 11>
1, the sensor current transformer 11 is provided in a high-voltage circuit 6H described later, and is a device that outputs a smaller sensor output current B from a high-voltage AC current H flowing through the high-voltage circuit 6H. Note that not only one sensor current transformer 11 but also multiple (e.g., two) sensor current transformers 11 may be present in one power system 1.
The electric path between the sensor current transformer 11 and the reverse power relay unit 12 (or the calculation unit 13) described later is a sensor output electric path 6B through which the sensor output current B flows, and the sensor output electric path 6B may be a set of two wires in the case of a single-phase two-wire (1φ2W) or the like, or a set of three wires in the case of a three-phase three-wire (3φ3W) or the like, and may be a set of multiple wires depending on the power distribution system (power transmission system). Note that when the sensor output electric path 6B is a three-phase three-wire system, as described above, it may be input to the reverse power relay unit 12 or the like as a single-phase two-wire system via an ammeter changeover switch (not shown).
A sensor output current B, which is a smaller current (e.g., 5 mA or a few mA, or 1 mA to 20 mA, etc.) corresponding to the current of the high-voltage AC current H flowing through the high-voltage circuit 6H, is output from the sensor current transformer 11 and flows through the sensor output circuit 6B.

The number of times (turns) that the winding of the sensor current transformer 11 is wound around the coil is not particularly limited, but may be, for example, 100 to 20,000 turns, preferably 500 to 10,000 turns, and more preferably 1,000 to 5,000 turns (e.g., 3,000 turns).
Since the number of turns of the high-voltage circuit 6H (and the current-transformed output circuit 6R described later) can be said to be one turn compared to the number of turns of the sensor current transformer 11, the current transformation ratio of the primary side (the side of the high-voltage circuit 6H, etc.) to the secondary side (output side) of the sensor current transformer 11 is 1:the number of turns of the sensor current transformer 11. The value of the current transformation ratio is not particularly limited, and may be, for example, 1:100 to 1:20,000, preferably 1:500 to 1:10,000, and more preferably 1:1,000 to 1:5,000 (e.g., 1:3,000).
The rated range of the current in the sensor current transformer 11 is not particularly limited, but may be, for example, 0.01 A or more and 5.00 A or less, or 1 A or more and 200 A or less (10 A, 60 A, etc.).
Furthermore, the maximum value of the range of current actually flowing through the sensor current transformer 11 may be 10 to 20 times the maximum value of the rated range of current described above, for example, 100 kA or less, preferably 80 kA or less, and more preferably 60 kA or less (e.g., 40 kA).

Incidentally, "the sensor current transformer 11 is provided in the high-voltage circuit 6H" means not only that the sensor current transformer 11 is provided directly in the high-voltage circuit 6H (for example, a switch-type (also called a split type, such as a fluxgate type or Hall element type) sensor current transformer 11 that can be installed on two of the three-phase three-wire high-voltage circuit (high-voltage cable) 6H without splitting each high-voltage cable 6H by opening and closing it itself and then attaching it later), but also that the sensor current transformer 11 is provided in the current transformer output circuit 6R (in other words, the secondary side of the instrument current transformer 11a) that flows the transformed output current R from the instrument current transformer 11a described later, and this current transformer output circuit 6R may be a single-phase two-wire (1φ2W) circuit or the like. Incidentally, the sensor current transformer 11 being provided on the current transformer output circuit 6R may mean, for example, that the sensor current transformer 11 is an open/close type that can be attached to each of the single-phase two-wire current transformer output circuits 6R without opening or closing each current transformer output circuit 6R, and that the sensor current transformer 11 can be retrofitted by opening and closing itself.
The instrument current transformer 11a will be described below.

<Instrument current transformer 11a>
As shown in FIG. 1, an instrument current transformer (CT) 11a is provided in a high-voltage circuit 6H described later, and is a device that transforms a high-voltage AC current H flowing through the high-voltage circuit 6H into a smaller transformed output current R.
As described above, the electric path between the instrument current transformer 11a and the above-mentioned overcurrent relay 5d is the current transformer output electric path 6R through which the current transformer output current R flows, and the current transformer output electric path 6R may also be a set of two electric paths in the case of a single-phase two-wire (1φ2W) or the like, or a set of three electric paths in the case of a three-phase three-wire (3φ3W) or the like, and may be a set of multiple electric paths depending on the power distribution system (power transmission system). Note that when the current transformer output electric path 6R is a three-phase three-wire system, it may be input to the overcurrent relay 5d as a single-phase two-wire system via an ammeter changeover switch (not shown) as described above.
A smaller current (e.g., about 10 A) of current transformer output current R corresponding to the high-voltage AC current H flowing through the high-voltage circuit 6H is output from the sensor current transformer 11 to the current transformer output circuit 6R and flows into the sensor output circuit 6B.

The number of times (turns) that the winding of the instrument current transformer 11a is wound around the coil is not particularly limited, but may be, for example, 10 to 10,000 turns, preferably 100 to 6,000 turns, and more preferably 500 to 4,000 turns (e.g., 1,500 turns).
Since the number of turns of the high voltage circuit 6H can be said to be one for the number of turns of the current transformer 11a, the current transformation ratio of the primary side (the high voltage circuit 6H side) and the secondary side (output side) of the current transformer 11a is 1: the number of turns of the current transformer 11a. The value of the current transformation ratio is not particularly limited, and may be, for example, 1:10 to 1:10000, preferably 1:100 to 1:6000, and more preferably 1:500 to 1:4000 (e.g., 1:1500).
The rated range of the current in the instrument current transformer 11a is not particularly limited, but may be, for example, 15 A or more and 1800 A or less, preferably 20 A or more and 1650 A or less, and more preferably 25 A or more and 1500 A or less (e.g., 60 A).
Furthermore, the maximum value of the range of the current actually flowing through the instrument current transformer 11a may be 10 to 20 times the maximum value of the rated range of the current described above, and may be, for example, 100 kA or less, preferably 80 kA or less, and more preferably 60 kA or less (e.g., 40 kA).

Incidentally, "the instrument current transformer 11a is provided in the high-voltage circuit 6H" means that the instrument current transformer 11a is provided directly in the high-voltage circuit 6H, and may be attached from the beginning by splitting each high-voltage cable 6H for two of the three-phase three-wire high-voltage circuit (high-voltage cable) 6H, or may be an open/close type (fluxgate type, Hall element type, etc.) instrument current transformer 11a that can be attached without splitting each high-voltage cable 6H and that opens and closes itself and is attached later.
The instrument current transformer 11a may be provided anywhere in the high-voltage circuit 6H, but may be provided, for example, between the vacuum circuit breaker 5a and the load switch 5c in the high-voltage circuit 6H.

<Reverse power relay unit 12>
As shown in FIG. 1, the reverse power relay unit 12 is connected to the instrument transformer 10 via the above-mentioned transformer output circuit 6S, and at the same time is connected to the sensor current transformer 11 (or connected to the calculation unit 13) via the above-mentioned sensor output circuit 6B, and is a part that detects a reverse power generation state based on the transformer output current S and the sensor output current B. When this reverse power relay unit 12 detects a reverse power generation state, it may output a signal to stop the conversion of the above-mentioned conversion unit 3.
Here, "detecting a reverse power generation state" means that, as described above, it has been determined that reverse power (power flowing back from the high-voltage power line 6H to the system K) has occurred, as calculated by the calculation unit 13 described later based on the transformer output current S and the sensor output current B, and that the reverse power has become equal to or greater than a predetermined value (threshold value).
In addition, "the reverse power becomes greater than a predetermined value" does not necessarily mean that the reverse power becomes greater than or equal to a threshold value strictly, but depending on the resolution and settings of the reverse power relay unit 12, it may also mean that the reverse power "becomes greater than or equal to a value that can be regarded as the threshold value", and the "value that can be regarded as the threshold value" may depend on the resolution of the reverse power relay unit 12, and may be, for example, the sum of the threshold value and 1 mA, 1 μA, 1 nA, etc.
Incidentally, this includes not only the case where a signal is output to the conversion unit 3 immediately after the reverse power becomes equal to or greater than a predetermined value (threshold value), but also the case where a signal is output after a predetermined time has elapsed.
Here, the "predetermined time" may be 0.1 seconds or more and 30.0 seconds or less, 0.2 seconds or more and 20.0 seconds or less, 0.3 seconds or more, or 15.0 seconds or more after the reverse power becomes equal to or greater than a predetermined value.

The output signal from the reverse power relay unit 12 may be directly input to the conversion unit 3, or may be input to a control device (described later) of the conversion unit 3 or to the calculation unit 13. When the output signal from the reverse power relay unit 12 is directly input to the conversion unit 3, the reverse power relay unit 12 can also be said to be a control device.
In one power system 1, the number of reverse power relay units 12 and the number of the above-mentioned instrument transformers 10 and sensor current transformers 11 may be the same or different, and the number may be one or more.
The power supply for the reverse power relay unit 12 is also connected to a capacitor device 9, which will be described later, an instrument transformer 10, and other uninterruptible power supplies (not shown), and can be said to be input from the capacitor device 9, etc.
The reverse power relay unit 12 can also be said to be a reverse power relay (RPR).

<Calculation unit 13>
As shown in FIG. 1, the calculation unit 13 is a part that calculates at least the power in the high-voltage circuit 6H based on the transformer output current S and the sensor output current B described above.
The calculation unit 13 is not particularly limited as long as it can calculate at least the power in the high-voltage circuit 6H, and may be, for example, electronic or mechanical, three-phase (a method of measuring two phases out of three phases and three wires), or single-phase.
Hereinafter, the calculation unit 13 will be described as being mainly electronic and three-phase.
The calculation unit 13 may calculate, in addition to the power in the high-voltage circuit 6H, for example, at least one of the current, voltage, power factor, and amount of power in the high-voltage circuit 6H based on the transformer output current S and the sensor output current B.
The calculation of power and the like in the calculation unit 13 may be performed at predetermined time intervals, and the predetermined time may be, for example, 0.01 seconds or more and 5.00 seconds or less (such as 0.1 seconds).
Furthermore, when the earth fault overvoltage relay unit 8 detects an earth fault overvoltage state or when the reverse power relay unit 12 detects a reverse power generation state, the calculation unit 13 may collectively stop the conversion of the conversion unit 3 via a signal to the conversion unit 3, and in this case, the calculation unit 13 may also be said to be a control device.
Also, the electric paths between the above-mentioned voltage transformer 10 or the sensor current transformer 11 and the reverse power relay unit 12 may be connected via the calculation unit 13, and even in the connection via the calculation unit 13, it can be said that the voltage transformer 10 and the reverse power relay unit 12 are connected via the transformer output electric path 6S, and the sensor current transformer 11 and the reverse power relay unit 12 are connected via the sensor output electric path 6R. In the connection via the calculation unit 13, the transformed AC current S from the voltage transformer 10 and the sensor output current R from the sensor current transformer 11 are first input to the calculation unit 13 to calculate the power (reverse power) in the high-voltage circuit 6H, and the calculated reverse power can be input from the calculation unit 13 to the reverse power relay unit 12.

<Device housing 14>
As shown in FIG. 1, the device housing 14 is a housing in which the above-mentioned earth fault overvoltage relay unit 8, reverse power relay unit 12, and calculation unit 13 are provided (built-in).
There are no particular limitations on the shape, size, configuration, etc. of the device housing 14 as long as it incorporates the earth fault overvoltage relay unit 8, the reverse power relay unit 12, and the calculation unit 13, but for example, the shape may be approximately cubic or approximately rectangular.
The device housing 14 may have a display unit that displays the power value calculated by the above-mentioned calculation unit 13, and this display unit is also not particularly limited in terms of its shape, size, position, configuration, etc., but for example, the shape may be approximately rectangular or approximately square.
The content displayed on the display unit may not only be the power value measured by the calculation unit 13, but may also include the integrated power (i.e., the amount of power) of that power, or numbers indicating the mode or state.

The device housing 14 may have an operation unit, and the operation unit is also not particularly limited in terms of its configuration, role, position, etc., and may be provided with a plurality of buttons, for example.
The role of the operation unit may be, for example, a button for turning the display unit on and off (display button), a reset button for resetting the electrical device 1, buttons for selecting a mode or state (such as a "+" button or a "-" button), or a set button for confirming (setting) a selected mode, etc.
The position of such an operation unit may be, for example, on the front surface of the device housing 14, below the display unit described above.
The device housing 14 may have a terminal portion (terminal block), and there are no particular limitations on the number or location of this terminal portion. For example, one device housing 14 may be provided with one terminal portion or multiple (e.g., three) terminal portions.
In this way, a device that incorporates multiple relay units, such as the earth fault overvoltage relay unit 8 and the reverse power relay unit 12, into a single device housing 14 can also be said to be a "composite relay device (composite relay) 20."
In the case of such a composite relay device 20, it can be said that the earth fault overvoltage relay unit 8, the reverse power relay unit 12, and the calculation unit 13 are connected to each other within the device housing 14, and therefore if the zero-phase output circuit 6Z from the zero-phase voltage detector 7, the capacitor output circuit 6D from the capacitor device 9, the transformer output circuit 6S from the instrument transformer 10, and the sensor output circuit 6B from the sensor current transformer 11 are connected to the composite relay device 20, it can be said that the zero-phase output circuit 6Z from the zero-phase voltage detector 7 and the capacitor output circuit 6D from the capacitor device 9 are connected to the earth fault overvoltage relay unit 8, and the transformer output circuit 6S from the instrument transformer 10 and the sensor output circuit 6B from the sensor current transformer 11 are connected to the reverse power relay unit 12. Furthermore, in the case of this composite relay 20, the power supply units of the earth fault overvoltage relay unit 8, the reverse power relay unit 12 and the calculation unit 13 may be combined into one, and this power supply unit has a power supply range corresponding to the voltage of the capacitor output current D input to the composite relay 20. For example, if the capacitor output current D is direct current, it may be compatible with DC 80V or more and 143V or less, or DC 20V or more and 56V or less, or if the capacitor output current D is alternating current, it may be compatible with AC 85V or more and 264V or less.

<Power generation circuit breaker 21, load 22, load transformer 23, load circuit breaker 24>
As shown in Fig. 1, the power generation circuit breaker 21 is a device capable of interrupting the low voltage AC current L from the converter 3 described above, in other words, it is a device provided in the low voltage line 6L described later and capable of interrupting the low voltage line 6L, and can also be said to be a low voltage circuit breaker. The power generation circuit breaker 21 may be a molded case circuit breaker (MCCB) or an earth leakage circuit breaker (ELCB). There may be not only one power generation circuit breaker 21 in one power system 1, but also a plurality of power generation circuit breakers 21. For example, as described above, when the low voltage line 6L branches between the transformer 4 and the converter 3 according to the number of converters 3, one power generation circuit breaker 21 may be provided between the branching point and the transformer 4, and one may be provided between the branching point and each converter 3.
1, the load 22 is a device that consumes power from the power generation unit 2 via the conversion unit 3, power from the system K via the system connection unit 5, the transformer 4, etc. The load 22 may have any configuration, and may be, for example, an industrial motor (power load) 22a in a factory, lighting (lighting load) 22b in a factory, a lighting distribution board connected to multiple lights 22b, or an air conditioner, fluorescent light, home appliance, vehicle such as an electric car or a gasoline car, or device in the vehicle in a building such as a house or a building.

As shown in FIG. 1, the load transformer 23 is a device that transforms (steps down) the power from the system K and the power from the power generating unit 2, and is a so-called transformer. The term "transformer" is an abbreviation for "transformer". The capacity of the load transformer 23 may be the same as that of the above-mentioned transformer 4, and the configuration of the load transformer 23 may be a two-winding transformer or the like. It can also be said that the primary side of the load transformer 23 is the high-voltage circuit 6H side, and its secondary side is the low-voltage side. In this case, there is no particular restriction on the specific values, but for example, the voltage of the primary side, which is the high-voltage circuit 6H side, may be the same as that of the above-mentioned transformer 4, and the voltage of the secondary side, which is the low-voltage side, may be 10V or more and 1000V or less, preferably 50V or more and 800V or less, and more preferably 100V or more and 600V or less (105V to 210V, etc.). There are no particular limitations on the connection method for the primary and secondary sides of the load transformer 23, but for example, the primary side, which is the high-voltage circuit 6H side, may be star-connected (Y connection), and the secondary side, which is the low-voltage side, may be single-phase three-wire (i.e., Y-three connection), or the order of primary and secondary sides may be Y-Δ connection, Y-Y connection, Δ-Y connection, or Δ-Δ connection. The load transformer 23 may also be an oil-immersed transformer or a dry transformer, and may also be equipped with a contact prevention plate or be class B grounded.
As shown in FIG. 1, the load circuit breaker 24 is a device capable of interrupting an electrical path between the load transformer 23 and the load 22 (lighting load 22b) described above, or an electrical path between the generating transformer 4 and the load 22 (power load 22a) described above, and may be a circuit breaker or a ground fault circuit interrupter.
Furthermore, since the secondary side of the above-mentioned transformer 4 is connected not only to the power generation unit 2 and the conversion unit 3, but also to the power load 22a, as described above, it can be said to function as both a power generation transformer and a load transformer.

<Control device>
The control device may be a device that is connected to the above-mentioned earth fault overvoltage relay unit 8, reverse power relay unit 12, etc., and inputs a stop signal output from the earth fault overvoltage relay unit 8 or reverse power relay unit 12 to perform control such as stopping the conversion of the above-mentioned conversion unit 3, and may be a smart logger, a sequencer, a computer, etc.
In one power system 1, the number of control devices may be one or more.
The power supply of the control device may be connected to an uninterruptible power supply (not shown) or the like and may be input from the uninterruptible power supply, etc. Furthermore, the user may directly touch the control device to monitor, change settings, operate, etc., but may also be remotely performed via the Internet, telephone lines, etc.

＜Other＞
The present invention is not limited to the above-described embodiment. The components of the power system 1 and the like, or the overall structure, shape, dimensions, and the like can be appropriately changed in accordance with the spirit of the present invention.
The power system 1 does not need to have an instrument transformer 10, a sensor current transformer 11, or a reverse power relay unit 12 within the system connection unit 5, and further, even when the earth fault overvoltage relay unit 8 detects an earth fault overvoltage state or when the reverse power relay unit 12 detects a reverse power generation state, a signal to stop the conversion of the conversion unit 3 may not be output to the conversion unit 3, and the earth fault overvoltage relay unit 8, the reverse power relay unit 12, and the calculation unit 13 may not be provided within a single device housing 14.
Furthermore, the power system 1 does not need to have the calculation unit 13 or the device housing 14 .

The power system 1 may have a storage unit for storing electricity, which may be the above-mentioned capacitor device 9 or an uninterruptible power supply device, or may be a storage battery (battery) such as a lead acid battery, a lithium ion battery, a nickel-metal hydride battery, or a nickel-cadmium battery, or may be a device that stores hydrogen generated by electrolysis of water using the power generated by the power generation unit 21, extracts electricity when necessary using a fuel cell, or stores electricity as kinetic energy using a flywheel or stores electricity as potential energy using pumped water. In this case, the storage unit may be connected to the above-mentioned conversion unit 3 or an electric circuit such as a low-voltage circuit 6L, and may be charged with electricity output from the power generation unit 2, or may flow the charged electricity to the load 22 to be consumed by the load 22 (self-consumption), or may flow the charged electricity to the system K if it is possible to sell the electricity.
In the power system 1, the above-mentioned system connection unit 5, zero-phase voltage detector 7, earth fault overvoltage relay unit 8, capacitor device 9, instrument transformer 10, sensor current transformer 11, reverse power relay unit 12, calculation unit 13, equipment housing 14, power generation circuit breaker 21, etc. may be provided within a single panel housing (in other words, a single distribution board).
In addition, a zero-phase voltage detector 7, an earth fault overvoltage relay unit 8, a capacitor device 9, an instrument transformer 10, a sensor current transformer 11, a reverse power relay unit 12, a calculation unit 13, an equipment housing 14, a power generation circuit breaker 21, etc. may be provided in a panel housing (such as a power generation connection board, an added board) separate from the panel housing (such as a system board, an existing board) in which the system connection unit 5 is provided.
In the power system 1, if the load 22, the load transformer 23 (the transformer 4 that serves as both a load transformer and a power generation transformer), the load breaker 24, and the system connection unit 5 already exist, it can be said that in order to turn these existing loads 22, etc. into a self-consumption type power generation plant, it is possible to retrofit the power generation unit 2, conversion unit 3, zero-phase voltage detector 7, earth fault overvoltage relay unit 8, capacitor device 9, sensor current transformer 11, reverse power relay unit 12, calculation unit 13, device housing 14, power generation breaker 21, etc. to the existing loads 22, etc.
The system K related to the power system 1 described above will be explained in detail below.

<Series K>
1, the grid K transmits (receives) electricity to the power system 1, and refers to the entire system through which electric power companies and the like supply electricity to consumers, and may also be called the power grid K. Specifically, the grid K includes facilities such as a substation, a transmission line, and a distribution line, and may also include a power plant. The grid K may also include the above-mentioned commercial transformer 31a, a power purchase watt-hour meter, a power sale watt-hour meter, a pole-mounted air switch, and a protective relay device.
The power handled by system K may be either AC or DC, but the following description will be given assuming that it is AC.
In system K, most of the electricity transmitted is AC, so it is transmitted using a three-phase, three-wire (3φ3W) transmission line. In order to reduce transmission losses during transmission, electricity is transmitted at as high a voltage as possible (for example, 6,600 V or 22,000 V) in the main long-distance transmission sections.
The electricity transmitted by system K is transformed (stepped down) in several stages at locations close to the consumption area, and after the pole-mounted transformer, the electricity is distributed via single-phase two-wire (1φ2W) or the like.
System K may be a system of a power company or the like (commercial power system), a system independently owned by an organization such as a company or a local government, or a system within a plant (independent power system).

The power system of the present invention can be used for self-consumption solar power plants and the like, regardless of the amount of power generated or the size of the plants. In addition to self-consumption solar power plants, the power system can also be used in non-self-consumption solar power plants and plants that generate power using generators (such as AC motors) rotated by wind, water, wave, geothermal, etc., and can be used both indoors and outdoors.

REFERENCE SIGNS LIST 1 Power system 2 Power generation unit 3 Conversion unit 4 Transformer 5 System connection unit 6H High voltage circuit 6Z Zero-phase output circuit 6D Capacitor output circuit 6S Transformer output circuit 6B Sensor output circuit 7 Zero-phase voltage detector 8 Earth fault overvoltage relay unit 9 Capacitor device 10 Instrument transformer 11 Sensor current transformer 12 Reverse power relay unit 13 Calculation unit 14 Device housing L Low voltage AC current H High voltage AC current Z Zero-phase output current S Transformer output current B Sensor output current K System

Claims (4)

A power system comprising: a power generation unit (2); a conversion unit (3) that converts a direct current or an alternating current from the power generation unit (2) into a low-voltage alternating current (L); a transformer (4) that transforms the low-voltage alternating current (L) from the conversion unit (3) into a higher-voltage alternating current (H); and a system connection unit (5) that connects the transformer (4) to a system (K),
The system connection unit (5)
A high-voltage circuit (6H) that connects the transformer (4) and a system (K) and passes a high-voltage AC current (H);
A zero-phase voltage detector (7) provided in the high-voltage power supply (6H);
an earth fault overvoltage relay unit (8) connected to a zero-phase output circuit (6Z) through which a zero-phase output current (Z) from the zero-phase voltage detector (7) flows and detecting an earth fault overvoltage state based on the zero-phase output current (Z);
a capacitor device (9) connected to a capacitor output circuit (6D) for supplying power from a power source to the earth fault overvoltage relay unit (8) and for supplying power from a power source to the earth fault overvoltage relay unit (8) during a power outage ;
The system connection unit (5) has an instrument transformer (10) that is provided in the high-voltage power line (6H) and transforms a high-voltage AC current (H) flowing through the high-voltage power line (6H) into a lower-voltage transformed output current (S),
The power system is characterized in that the capacitor device (9) is charged with electricity from the potential transformer (10) via a capacitor input circuit (6D') branching off from a transformer output circuit (6S) through which a transformed output current (S) from the potential transformer (10) flows . The system connection unit (5)
a sensor current transformer (11) provided in the high voltage power supply (6H) and outputting a smaller sensor output current (B) from the high voltage AC current (H) flowing through the high voltage power supply (6H);
a reverse power relay unit (12) connected to a transformer output circuit (6S) through which a transformer output current (S) from the instrument transformer (10) flows and a sensor output circuit (6B) through which a sensor output current (B) from the sensor current transformer (11) flows, and detecting a reverse power generation state based on the transformer output current (S) and the sensor output current (B) ;
a current transformer (11a) for instrumentation that is provided in the high-voltage power supply (6H) and transforms a high-voltage AC current (H) flowing through the high-voltage power supply (6H) into a smaller current transformer output current (R) ;
A current transformer output circuit (6R) through which a current transformer output current (R) from the current transformer (11a) flows is a single-phase two-wire circuit,
2. The power system according to claim 1 , wherein the sensor current transformer (11) is provided for each of the two wires of the single-phase two-wire current transformer output circuit (6R) . 3. A power system according to claim 2, characterized in that, when the reverse power relay unit (12) in the power system detects a reverse power generation state, the reverse power relay unit (12) stops conversion of the conversion unit (3) (excluding parallel-off of the conversion unit (3)) via a signal to the conversion unit (3). The earth fault overvoltage relay unit (8) and the reverse power relay unit (12),
a calculation unit (13) that calculates at least the power in the high voltage line (6H) based on the transformer output current (S) and the sensor output current (B);
Located in one device housing (14) ,
The reverse power relay unit (12) and the potential transformer (10) are connected via the calculation unit (13),
3. The power system according to claim 2 , wherein the reverse power relay unit (12) and the sensor current transformer (11) are also connected via the calculation unit (13) .