Zero phase voltage detector and power system

Abstract

To achieve "space saving / cost reduction" and "reduction of electric shock risk" by setting the capacitance of a voltage dividing capacitor to a value corresponding to a shielded cable by a zero phase voltage detector.SOLUTION: A zero phase voltage detector 1 provided in an electric path has a voltage detecting capacitor 2, a zero phase cable 3 which is a shielded cable, a voltage dividing capacitor 4, and a zero phase transformer 5, and the capacitance of the voltage dividing capacitor 4 is set to a value corresponding to the zero phase cable 3 as a capacitor. The voltage dividing capacitor 4 may include an internal capacitor 4a inside the zero phase housing 6 and an external capacitor 4b outside the zero phase housing 6. The system connecting unit 14 includes a high-voltage circuit 15H provided with the zero phase voltage detector 1, a ground-fault over-voltage relay unit 16 that detects a ground-fault over-voltage based on a zero phase current Z from the zero phase voltage detector 1, and a capacitor device 17 that supplies power to the ground-fault over-voltage relay unit 16 at the time of a power failure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a zero-phase-sequence voltage detector provided in an electric line and a power system including the zero-phase-sequence voltage detector. [Background technology]

[0002] BACKGROUND ART Conventionally, an earthing voltage transformer (EVT) for extra-high voltage is known (see Patent Document 1). As shown in FIG. 3 of Patent Document 1, this earthed potential transformer is connected to an extra-high voltage bus through which an extra-high voltage current (e.g., 22,000 V, 33,000 V, 77,000 V, etc.) flows, and as shown in claim 1, etc., the earthed potential transformer includes first, second, and third partial transformers corresponding to the first, second, and third phases in a three-phase AC power supply system, and each of the first to third partial transformers has a star-connected primary winding, a star-connected secondary winding, and an open delta-connected tertiary winding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-054467 Summary of the Invention [Problem to be solved by the invention]

[0004] When adding self-consumption equipment to an existing substation, the grounded potential transformer described in Patent Document 1 and the like needs to be modified. However, the grounded potential transformers described in Patent Document 1 and elsewhere are very large and heavy, so many existing substations do not have the space to add or modify grounded potential transformers, and the cost of such modifications would be very high. In addition, there is a risk of electric shock from busbars carrying extra-high voltage currents and from equipment installed on those busbars, as electricity can flow through the human body even if one does not come into direct contact with them by simply approaching them.

[0005] In view of the above, the present invention aims to provide a zero-phase voltage detector and a power system that can achieve "space savings and cost reduction" and "reduced risk of electric shock" by setting the capacitance of the voltage dividing capacitor in the zero-phase voltage detector to a value that corresponds to the zero-phase cable that is both a shielded cable and a capacitor. [Means for solving the problem]

[0006] The zero-phase voltage detector 1 according to the present invention is a zero-phase voltage detector to be installed in an electric circuit, the electric circuit being a three-phase, three-wire circuit. The zero-phase voltage detector comprises: a voltage detection capacitor 2 having one voltage detection end 2A connected to each of the three wires of the electric circuit; a zero-phase cable 3 having the other voltage detection ends 2B of the voltage detection capacitors 2 connected together at one cable end 3A; a voltage dividing capacitor 4 having one voltage dividing end 4A connected to the other cable end 3B of the zero-phase cable 3 and the other voltage dividing end 4B grounded; and a zero-phase transformer 5 that transforms and outputs the voltage between the one voltage dividing end 4A and the other voltage dividing end 4B of the voltage dividing capacitor 4. The zero-phase cable 3 is a shielded cable in which a conductive core wire 3a is covered with a conductive shield layer 3c with an insulator 3b sandwiched therebetween. The zero-phase cable 3 is used as a capacitor that stores electric charge between the conductive core wire 3a and the conductive shield layer 3c. The capacitance of the voltage dividing capacitor 4 is set to a value corresponding to the zero-phase cable 3.

[0007] A second feature of the zero-phase voltage detector 1 according to the present invention is that, in addition to the first feature, the zero-phase voltage detector has a zero-phase housing 6 incorporating the zero-phase transformer 5, and the voltage dividing capacitor 4 comprises an internal voltage dividing capacitor 4a incorporated in the zero-phase housing 6 and an external voltage dividing capacitor 4b connected in parallel to the internal voltage dividing capacitor 4a and provided outside the zero-phase housing 6.

[0008] A power system 10 according to the present invention is a power system having the above-described zero-phase voltage detector 1, and the power system includes a power generation unit 11, a conversion unit 12 that converts a DC current or an AC current from the power generation unit 11 into a low-voltage AC current L, a system transformer 13 that can transform the low-voltage AC current L from the conversion unit 12 into a higher-voltage AC current H, and a system connection unit 14 that connects the system transformer 13 to a system K, and the system connection unit 14 connects the system transformer 13 and the system K to convert the high-voltage AC current The first feature of the zero-phase-sequence voltage detector is that it has a high-voltage circuit 15H through which a current H flows and in which the zero-phase-sequence voltage detector 1 is provided, an earth fault overvoltage relay unit 16 connected to a zero-phase output circuit 15Z through which a zero-phase output current Z output from the zero-phase-sequence transformer 5 in the zero-phase-sequence voltage detector 1 flows and which detects an earth fault overvoltage state based on the zero-phase output current Z, and a capacitor device 17 connected to a capacitor output circuit 15C which supplies power from a power source to the earth fault overvoltage relay unit 16 and which supplies power from a power source to the earth fault overvoltage relay unit 16 during a power outage.

[0009] A second feature of the power system 10 according to the present invention is a power system having a zero-phase voltage detector, the power system including a power generation unit 11, a conversion unit 12 that converts a DC current or an AC current from the power generation unit 11 into a low-voltage AC current L, a system transformer 13 that can transform the low-voltage AC current L from the conversion unit 12 into a higher voltage AC current H, and a system connection unit 14 that connects the system transformer 13 to a system K, and the system connection unit 14 is connected between the system transformer 13 and the system K. The zero-phase voltage detector includes a high-voltage circuit 15H through which a high-voltage AC current H flows and which is provided with the zero-phase voltage detector; a ground fault overvoltage relay unit 16 connected to a zero-phase output circuit 15Z through which a zero-phase output current Z output from a zero-phase transformer 5 in the zero-phase voltage detector flows and which detects a ground fault overvoltage state based on the zero-phase output current Z; and a capacitor device 17 connected to a capacitor output circuit 15C which supplies power from a power source to the ground fault overvoltage relay unit 16 and which supplies power from a power source to the ground fault overvoltage relay unit 16 during a power outage.

[0010] As a third feature of the power system 10, in addition to the first or second feature, the system connection unit 14 may also include a voltage transformer 20 that is provided in the high-voltage circuit 15H and transforms the high-voltage AC current H flowing in the high-voltage circuit 15H into a lower-voltage transformed output current S, a sensor current transformer 21 that is provided in the high-voltage circuit 15H and outputs a smaller sensor output current B from the high-voltage AC current H flowing in the high-voltage circuit 15H, and a reverse power relay unit 22 that is connected to a transformer output circuit 15S through which the transformed output current S from the voltage transformer 20 flows and to a sensor output circuit 15B through which the sensor output current B from the sensor current transformer 21 flows, and that detects a reverse power generation state based on the transformed output current S and the sensor output current B.

[0011] In addition, a fourth feature of the power system 10 is that when the earth fault overvoltage relay unit 16 in the power system of the first or second feature detects an earth fault overvoltage state, the conversion of the conversion unit 12 may be stopped via a signal to the conversion unit 12, and / or when the reverse power relay unit 22 in the power system of the third feature detects a reverse power generation state, the conversion of the conversion unit 12 may be stopped via a signal to the conversion unit 12.

[0012] Furthermore, a fifth feature of the power system 10 is that, in addition to the third feature, the earth fault overvoltage relay unit 16, the reverse power relay unit 22, and a calculation unit 23 that calculates at least the power in the high-voltage circuit 15H based on the transformer output current S and the sensor output current B may be provided within a single device housing 24.

[0013] Due to these features, by providing a zero-phase sequence voltage detector 1 having a voltage detection capacitor 2, a zero-phase sequence cable 3, a voltage dividing capacitor 4, and a zero-phase sequence transformer 5 in an electrical circuit, unlike Patent Document 1, even when adding self-consumption equipment to an existing substation, simply providing a smaller, lighter, and lower-cost zero-phase sequence voltage detector 1 eliminates the need for additional space or costs for additional modifications to a grounded instrument transformer, thereby achieving "space savings and cost reductions." In addition, by setting the capacitance of the voltage dividing capacitor 4 to a value that corresponds to the zero-phase cable 3 (length, etc.), which is a shielded cable and also serves as a capacitor, even if the zero-phase cable 3 is lengthened, the voltage value output from the zero-phase transformer 5 to equipment such as the earth fault overvoltage relay unit 16 when an earth fault occurs on the electrical circuit side can be set to a value within a certain range that is suitable for equipment such as the earth fault overvoltage relay unit 16, making it unnecessary to change equipment such as the earth fault overvoltage relay unit 16.Even if the voltage value of the current flowing in the electrical circuit is extra-high voltage, by making the zero-phase cable 3 sufficiently long, a safe distance can be secured between the voltage detecting capacitor 2 and the voltage dividing capacitor 4, and this can reduce the risk of electric shock in a zero-phase voltage detector 1 installed in an electrical circuit through which extra-high voltage or other current flows.

[0014] Furthermore, by providing not only the internal voltage dividing capacitor 4a inside the zero-phase housing 6 but also the external voltage dividing capacitor 4b outside the zero-phase housing 6, it is possible to convert, for example, a zero-phase voltage detector for 6600V into one for extra-high voltage use simply by retrofitting the external voltage dividing capacitor 4b so that the capacitance of the entire voltage dividing capacitor 4 is a value corresponding to the zero-phase cable 3, which further simplifies additional modifications even when adding self-consumption equipment to an existing substation.

[0015] Furthermore, by providing a capacitor device 17 that supplies power to the earth fault overvoltage relay unit 16 during a power outage, which detects an earth fault overvoltage state based on the zero-phase output current Z from the zero-phase voltage detector 1, the power supply to the earth fault overvoltage relay unit 16 does not stop even if a power outage occurs along with an earth fault, and a signal can be output from the earth fault overvoltage relay unit 16, making it possible to detect an earth fault overvoltage state even during a power outage.

[0016] In addition, by having a reverse power relay unit 22 that detects a reverse power generation state based on the transformer output current S from the instrument transformer 20 and the sensor output current B from the sensor current transformer 21, it is possible to prevent or reduce the power generated by the power generation unit 11 from flowing back into the system K via the conversion unit 12, system transformer 13, and system connection unit 14.

[0017] In addition, when the earth fault overvoltage relay unit 16 detects an earth fault overvoltage state or when the reverse power relay unit 22 detects a reverse power generation state, the conversion of the conversion unit 12 is stopped via a signal to the conversion unit 12, thereby preventing the power generated by the power generation unit 11 via the conversion unit 12 from flowing back into the system K. In addition, when the conversion of the conversion unit 12 is stopped, it is not necessary to adjust the output from the conversion unit 12 to the voltage and phase of the system K when the conversion is resumed. Therefore, it can be said that the power system 10 can be restored in a shorter time and with less effort than if any of the electrical paths from the conversion unit 12 to the system K were cut off.

[0018] In addition, by arranging the earth fault overvoltage relay unit 16, the reverse power relay unit 22, and the calculation unit 23 that calculates the power of the high voltage circuit 15H, etc., within one device housing 24, space can be saved by the amount of space that is provided within one device housing 24, and sufficient space can be secured to install other equipment. In addition, if the relay unit and calculation unit are separate devices, the minute errors that occur in each unit will be different, so malfunctions such as the relay unit detecting a reverse power generation state on its own will not occur, and malfunctions can be reduced. [Effects of the Invention]

[0019] According to the zero-phase voltage detector and power system of the present invention, by setting the capacitance of the voltage dividing capacitor in the zero-phase voltage detector to a value that corresponds to the zero-phase cable being a shielded cable and also serving as a capacitor, it is possible to achieve "space savings and cost reductions" and "reduction of the risk of electric shock." [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram illustrating a zero-phase voltage detector according to the present invention; [Figure 2] 1 is a schematic diagram showing a power system according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. <Overall configuration of zero-phase voltage detector 1> 1 and 2 show a zero phase potential device (ZPD) 1 according to the present invention. This zero-phase voltage detector 1 is an apparatus installed in an electric circuit D, and includes a voltage detecting capacitor 2, a zero-phase cable 3, a voltage dividing capacitor 4, and a zero-phase transformer 5. The zero-phase voltage detector 1 may have a zero-phase housing 6, which will be described later. Additionally, the zero-phase voltage detector 1 may have a test capacitor 1a and a test terminal, which will be described later.

[0022] In addition, the "electrical circuit D" and other electrical circuits in this invention are those that carry electricity (current), and include conductors such as copper, aluminum, silver, gold, and nichrome, cables in which these conductors are covered with insulation, and general electrical wires. This electric circuit D is a three-phase three-wire (3φ3W) circuit, and includes a high-voltage circuit 15H to be described later, and the zero-phase voltage detector 1 may be provided in the high-voltage circuit 15H. In this case, the zero-phase sequence voltage detector 1 can be said to be a device that detects whether a ground fault has occurred somewhere in the system, such as on the high-voltage line 15H side, causing a zero-phase sequence voltage on the high-voltage line 15H side. The zero-phase voltage detector 1 is also called a zero-phase voltage transformer (ZVT).

[0023] Here, the current, voltage, power, and capacity in the present invention may be values ​​within a rated range, in which case they can be referred to as rated current, rated voltage, rated power, and rated capacity. These rated currents, etc. can also be referred to as limit values ​​of current, etc. guaranteed by manufacturers for the safe use of electrical appliances, and further, ratings can also be referred to as usage limits or conditions that guarantee the safe and proper operation of devices and equipment. When the current in the present invention is an AC current, the current value (current value), voltage value (voltage value), power value (power value), and capacitance value (capacity value) may be effective values.

[0024] The voltage value of the current flowing through the electric circuit D is not particularly limited, and may be, for example, an extra-high voltage value (also called extra-high voltage, a voltage value exceeding 7000V such as 22000V, 33000V, or 77000V), or a high voltage value (a voltage value exceeding 600V and not exceeding 7000V (e.g., 6600V) if the current is AC, or exceeding 750V and not exceeding 7000V if the current is DC), or a low voltage value (a voltage value not exceeding 600V if the current is AC, or not exceeding 750V if the current is DC). Hereinafter, the voltage value of the current flowing through the electric circuit D will be mainly described as being extra-high voltage.

[0025] <Voltage detection capacitor 2> As shown in FIGS. 1 and 2, the electroscopic capacitor 2 is a capacitor for detecting the zero-phase voltage generated in the electric path D described above. The voltage detection capacitors 2 are arranged in a set of three, with one voltage detection end 2A connected to each phase of the three-phase, three-wire circuit D (this can also be said to be three capacitors divided into three parts, each with a capacitance corresponding to the voltage value of the current flowing through circuit D). The other voltage detection ends 2B of these three voltage detection capacitors 2 are joined together and connected to one cable end 3A of a zero-phase cable 3, which will be described later. Furthermore, since there is an insulator (or dielectric) between the electrode at one end 2A of the electrodetector capacitor 2 and the electrode at the other end 2B of the electrodetector capacitor 2, it can be said that the electrodetector capacitor 2 is basically insulated between the one end 2A of the electrodetector capacitor 2 and the other end 2B of the electrodetector capacitor 2.

[0026] The specific configuration of the electroscopic capacitor 2 is not particularly limited, but may be, for example, an insulator type in which a capacitor is provided inside an insulator such as a synthetic resin such as epoxy resin, or porcelain, glass, etc. In the case of this insulator type, for example, a line post insulator (LP insulator) having a substantially cylindrical shape with multiple folds, a station post insulator, a long-rod insulator, etc. may also be used, as well as a suspension insulator, a pin insulator, etc. If the voltage detector capacitor 2 is a substantially cylindrical line post insulator, its upper end is a voltage detector end 2A (also called a high-voltage terminal) connected to an electric circuit D such as a high-voltage circuit 15H, and its lower end is a voltage detector end 2B (also called a low-voltage terminal) connected to a zero-phase cable 3 (described later). It may be. A mounting bracket may be provided on the lower end side of the substantially cylindrical electroscopic capacitor 2. The capacitor provided inside the insulator of the electroscopic capacitor 2 may be one or more ceramic capacitors (porcelain capacitors), and if there are more than one, the capacitors may be connected in series.

[0027] The capacitance of the electroscopic capacitor 2 is not particularly limited, but may be, for example, 1 pF to 10,000 pF, preferably 10 pF to 5,000 pF, and more preferably 50 pF to 1,000 pF (125 pF, 375 pF, approximately 83.333 pF, 250 pF, 750 pF, etc.), or may be a value corresponding to the voltage value of the current flowing through the electric circuit D. Specifically, if the voltage value of the current flowing through the electric circuit D is 22,000 V, the capacitance of each electroscopic capacitor 2 is 125 pF. (i.e., 375pF for the set of three electrodetector capacitors 2 as a whole), or if it is 33,000V, the capacitance of each electrodetector capacitor 2 can be approximately 83.333pF (i.e., 250pF for the set of three electrodetector capacitors 2 as a whole, so the capacitance of each capacitor is 250 / 3pF to be precise), or if it is 6,600V, the capacitance of each electrodetector capacitor 2 can be 250pF (i.e., 750pF for the set of three electrodetector capacitors 2 as a whole). Furthermore, the capacitance of each of the three electrodetector capacitors 2 in a set of three does not need to be exactly the same value, and as long as the capacitance of the three electrodetector capacitors 2 combined is a value corresponding to the voltage value of the current flowing in the electric circuit D, the capacitance of each of the electrodetector capacitors 2 may be slightly different (for example, if the voltage value of the current flowing in the electric circuit D is 22,000 V, the capacitance of each of the electrodetector capacitors 2 may be slightly greater or slightly less than 125 pF, but the capacitance of the set of three electrodetector capacitors 2 as a whole may be 250 pF).

[0028] <Zero-phase cable 3, conductive core wire 3a, insulator 3b, conductive shield layer 3c, etc.> As shown in FIGS. 1 and 2, the zero-phase cable 3 is a cable in which the other voltage detection ends 2B of the voltage detection capacitors 2 are gathered together and connected to one cable end 3A. The other cable end 3B of this zero-phase cable 3 is connected to one voltage dividing end 4A of a voltage dividing capacitor 4, which will be described later. The zero-phase cable 3 includes a conductive core wire 3a, an insulator 3b, and a conductive shield layer 3c, which will be described later. The zero-phase cable 3 is used as a capacitor that stores electric charge between the conductive core wire 3a and the conductive shield layer 3c. It can be said that the capacitance value of the voltage dividing capacitor 4, which will be described later, is determined depending on the length, capacitance, etc. of this zero-phase cable 3. Additionally, the zero-phase cable 3 may have a sheath or a shield wire, which will be described later.

[0029] The conductive core wire 3a in the zero-phase cable 3 is a wire that allows electricity (current) to flow, like the above-mentioned electric circuit D, and is made of a conductor (conductive material) such as copper, aluminum, silver, gold, or nichrome, and is located at the center (the core of the cable, so to speak) of the entire zero-phase cable 3. One zero-phase cable 3 may have one or more conductive core wires 3a. The insulator 3b in the zero-phase cable 3 is a non-conductor that does not allow electricity (current) to flow through it. It is made of materials such as polyvinyl chloride (PVC) resin, natural rubber, polyethylene (PE) resin, synthetic resins such as polyester resin, epoxy resin, melamine resin, phenolic resin, and polyurethane (PU) resin, as well as glass fiber, porcelain, cotton, paper, and mica. It covers the conductive core wire 3a throughout the zero-phase cable 3. The insulator 3b may be tape-shaped. When a single zero-phase cable 3 has multiple conductive core wires 3a, the insulator 3b may cover each of the conductive core wires 3a. The conductive shield layer 3c in the zero-phase cable 3 also allows electricity (current) to flow and is made of, for example, a braided strand of metal such as copper, aluminum, tin, or tin-plated annealed copper, or an unbraided spiral winding of metal tape such as copper, aluminum, tin, or tin-plated annealed copper, or a layer of a conductive polymer, and further covers the insulator 3b described above for the entire zero-phase cable 3. When one zero-phase cable 3 has multiple conductive core wires 3a, the conductive shield layer 3c may also be configured to cover each of the conductive core wires 3a and the insulators 3b.

[0030] Additionally, the sheath (coating or sheath) of the zero-phase cable 3 further covers the conductive shield layer 3c and is also called a jacket. The sheath is made of materials such as natural rubber, chloroprene (CR) rubber, and polyvinyl chloride (PVC) resin. When one zero-phase cable 3 has multiple conductive core wires 3a, insulators 3b, and conductive shield layers 3c, the sheath may be configured to cover all of the conductive core wires 3a, insulators 3b, and conductive shield layers 3c together. The shield wire in the zero-phase cable 3 is an electric circuit that is electrically connected to the conductive shield layer 3c, and like the conductive core wire 3a and the electric circuit D, it conducts electricity (current) and is made of a conductor (conductive material) such as copper, aluminum, silver, gold, or nichrome. The shield wire may also be covered with a sheath. When a single zero-phase cable 3 has multiple conductive shield layers 3c, the shield wire may be configured to connect all of the conductive shield layers 3c together into a single shield wire. Alternatively, the shield wire may be located at only one end of the conductive shield layer 3c. In this case, the conductive shield layer 3c is grounded at one end by grounding the shield wire. Alternatively, the shield wire may be located at both ends of the conductive shield layer 3c. In this case, the conductive shield layer 3c is grounded at both ends by grounding the shield wire.

[0031] The zero-phase cable 3 described above can also be said to be used as a capacitor that stores electric charge between the conductive core wire 3a and the conductive shield layer 3c. The capacitance of the zero-phase cable 3 as a capacitor is not particularly limited, but may be, for example, 0.1 μF / 1 km or more and 100.0 μF / 1 km or less (i.e., 0.0001 μF / m or more and 0.1000 μF / m or less (0.00036 μF / m, etc.)). In other words, if the zero-phase cable 3 is a cable with a uniform capacitance per unit length, the longer it is, the greater its capacitance will be. The length of the zero-phase cable 3 is not particularly limited, but may be, for example, 1 m or more and 30 m or less, preferably 1 m or more and 20 m or less, and more preferably 2 m or more and 15 m or less (10 m, 3 m, 3.6 m, 5 m, etc.). For example, the capacitance of the zero-phase cable 3 having a length of 10 m is 0.0005 μF or more and 1.0000 μF or less, preferably 0.0010 μF or more and 0.1000 μF or less, and more preferably Preferably, the capacitance is 0.0020 μF or more and 0.0500 μF or less (0.0036 μF, 0.0105 μF, etc.), and the capacitance of a 3.6 m long zero-phase cable 3 may be 0.0001 μF or more and 0.3500 μF or less, preferably 0.0003 μF or more and 0.0350 μF or less, and even more preferably 0.0006 μF or more and 0.0160 μF or less (0.0013 μF, etc.). The length of such a zero-phase cable 3 can also be said to be the safety distance between the above-mentioned voltage detection capacitor 2 and the voltage dividing capacitor 4 described later, and the longer the zero-phase cable 3, the longer the safety distance between the voltage detection capacitor 2 and the voltage dividing capacitor 4, thereby reducing the risk of electric shock.

[0032] <Voltage dividing capacitor 4> As shown in Figures 1 and 2, the voltage dividing capacitor 4 is a capacitor for dividing the voltage generated at the other end (low-voltage side terminal) 2B of the above-mentioned voltage detecting capacitor 2 when a zero-phase voltage occurs in the above-mentioned electric circuit D. One voltage dividing end 4A of the voltage dividing capacitor 4 is also called the N terminal and is connected to the other cable end 3B of the zero-phase cable 3 mentioned above, and the other voltage dividing end 4B of the voltage dividing capacitor 4 is also called the E terminal and is grounded (such as type A grounding). Furthermore, in the voltage-dividing capacitor 4, there is an insulator (or dielectric) between the electrode at one voltage-dividing end 4A and the electrode at the other voltage-dividing end 4B, so it can be said that the voltage-dividing capacitor 4 is also basically insulated between the one voltage-dividing end 4A and the other voltage-dividing end 4B. The voltage dividing capacitor 4 may also include an internal voltage dividing capacitor 4a and an external voltage dividing capacitor 4b, which will be described later.

[0033] The capacitance of the voltage dividing capacitor 4 is set to a value according to the above-mentioned zero-phase cable 3 (its length, capacitance, etc.). The capacitance of such a voltage dividing capacitor 4 is not particularly limited, but may be, for example, 0.01 μF or more and 10.00 μF or less, preferably 0.02 μF or more and 5.00 μF or less, and more preferably 0.05 μF or more and 1.00 μF or less (such as 0.2508 μF or 0.1568 μF).

[0034] <Internal voltage dividing capacitor 4a, external voltage dividing capacitor 4b> As shown in FIG. 1, the internal voltage dividing capacitor 4a is a part of the voltage dividing capacitor 4 described above, and is a capacitor built into the zero-phase housing 6 described later. The internal voltage dividing capacitor 4a has its internal voltage dividing end 4aA connected to the other cable end 3B of the zero-phase cable 3 described above, and its internal voltage dividing end 4aB is also called the E terminal as described above and is grounded. The internal voltage dividing capacitor 4a is connected in parallel with an external voltage dividing capacitor 4b, which will be described later. The capacitance of such an internal voltage dividing capacitor 4a is not particularly limited, but may be, for example, 0.01 μF to 10.00 μF, preferably 0.02 μF to 5.00 μF, and more preferably 0.05 μF to 1.00 μF (such as 0.1568 μF). The capacitance of the internal voltage dividing capacitor 4a may be the capacitance of a single capacitor or the total capacitance of multiple capacitors connected in parallel. If it is the total capacitance of multiple capacitors, the capacitances of the capacitors may be approximately the same or different (for example, 0.1500 μF and 0.0068 μF).

[0035] As shown in FIG. 1, the external voltage dividing capacitor 4b is a part of the voltage dividing capacitor 4 described above, and is a capacitor provided outside the zero-phase housing 6 described later. The external voltage dividing capacitor 4b is connected in parallel with the above-mentioned internal voltage dividing capacitor 4a. Strictly speaking, one external voltage dividing end 4bA of the external voltage dividing capacitor 4b is connected to one internal voltage dividing end 4aA of the internal voltage dividing capacitor 4a, and the other external voltage dividing end 4bB is connected to the other internal voltage dividing end 4aB of the internal voltage dividing capacitor 4a. Therefore, the capacitance of the voltage dividing capacitor 4 as a whole is the sum of the capacitance of the internal voltage dividing capacitor 4a and the capacitance of the external voltage dividing capacitor 4b. The capacitance of such external voltage dividing capacitor 4b is not particularly limited, but may be, for example, 0.01 μF to 10.00 μF, preferably 0.02 μF to 5.00 μF, and more preferably 0.05 μF to 1.00 μF (such as 0.094 μF). The capacitance of the external voltage dividing capacitor 4b may be the capacitance of a single capacitor or the total capacitance of multiple capacitors connected in parallel. If it is the total capacitance of multiple capacitors, the capacitance of each capacitor may be approximately the same value (e.g., 0.047 μF × 2) or may be different values. The external voltage dividing capacitor 4b may be built in a housing (so-called external housing 4b') separate from the zero-phase housing 6 described later.

[0036] <Zero-phase transformer 5> As shown in Figures 1 and 2, the zero-phase transformer 5 is a transformer that transforms (steps down) the voltage (divided voltage V2) between the voltage-dividing terminal 4A and the other voltage-dividing terminal 4B of the voltage-dividing capacitor 4 described above and outputs it. When a ground fault occurs on the electric circuit D side and the zero-phase sequence voltage detector 1 (voltage detector capacitor 2) detects a zero-phase sequence voltage, the zero-phase sequence transformer 5 outputs a zero-phase sequence output current Z of a lower voltage (for example, about 1 V, about 0.0 to 1.0 V, or about 6 to 9 V) corresponding to the zero-phase sequence voltage generated on the electric circuit D side. Note that the zero-phase sequence transformer 5 can also be said to be a zero-phase sequence converter, because it converts the divided voltage V2 of the voltage dividing capacitor 4 into a voltage value within a certain range suitable for devices such as the earth fault overvoltage relay unit 16. In the zero-phase transformer 5, the ratio of the primary side, which is the voltage dividing capacitor 4 side, to the secondary side, which is the output side, is not particularly limited, but may be, for example, primary side:secondary side = 2:1 or more and 100:1 or less (e.g., 20:1), and it can also be said that the zero-phase transformer 5 is insulated between the primary side and the secondary side. On the secondary side of the zero-phase transformer 5, the terminal corresponding to one voltage dividing end 4A of the voltage dividing capacitor 4 is also called the Y1 terminal, and the terminal corresponding to the other voltage dividing end 4B of the voltage dividing capacitor 4 is also called the Y2 terminal, and both are grounded (such as type D grounding).

[0037] <Length of the zero-phase cable 3 in the zero-phase voltage detector 1 and the risk of electric shock> The following points will be made regarding the zero-phase sequence voltage detector 1 described above. Originally (conventionally), it was considered better for the length of the zero-phase cable 3 to be shorter, because the capacitance of the zero-phase cable 3 would be negligibly small, and the voltage value of the zero-phase output current Z from the zero-phase transformer 5 would be within a certain range suitable for equipment such as the earth fault overvoltage relay unit 16, simply by appropriately setting the capacitance of the voltage divider capacitor 4. However, if the length of the zero-phase cable 3 is short, and the current flowing through the electric circuit D is extra-high voltage, although there is basically insulation between the electric circuit D side and the side of the voltage detector capacitor 2, the voltage dividing capacitor 4, etc., when a ground fault occurs on the electric circuit D side and a large current flows, there is a possibility that a large current will flow to the side of the equipment such as the voltage dividing capacitor 4 side, the zero-phase transformer 5 side, and the earth fault overvoltage relay unit 16, which will pose a risk of electric shock to the side of the equipment such as the voltage dividing capacitor 4 side, the zero-phase transformer 5 side, and the earth fault overvoltage relay unit 16, which people should be able to approach (where the voltage should be low).

[0038] <Output voltage value of zero-phase transformer 5 and capacitance of zero-phase cable 3 and voltage dividing capacitor 4> Therefore, in the zero-phase voltage detector 1 of the present invention, the capacitance of the voltage dividing capacitor 4 is set to a value corresponding to the shielded zero-phase cable 3, which is a capacitor (its length, capacitance, etc.).This means that even if the zero-phase cable 3 is made longer, the voltage value of the zero-phase output current Z from the zero-phase transformer 5 to equipment such as the earth fault overvoltage relay unit 16 when an earth fault occurs on the electric circuit D side is kept within a certain range suitable for equipment such as the earth fault overvoltage relay unit 16, making it unnecessary to change equipment such as the earth fault overvoltage relay unit 16.Even if the voltage value of the current flowing in the electric circuit D is extra-high voltage, by making the zero-phase cable 3 sufficiently long, a safe distance can be secured between the voltage detecting capacitor 2 and the voltage dividing capacitor 4, and this can reduce the risk of electric shock in a zero-phase voltage detector 1 installed in an electric circuit D through which extra-high voltage or other current flows. Here, in the present invention, "the capacitance of the voltage dividing capacitor 4 is set to a value corresponding to the zero-phase cable 3" means, for example, <1> The capacitance of the voltage dividing capacitor 4 is set to a value obtained by subtracting the capacitance of the zero-phase cable 3 from the capacitance of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is negligibly small (i.e., the theoretical or ideal capacitance value) (i.e., the capacitance of the voltage dividing capacitor 4 = the capacitance of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is negligibly small - the capacitance of the zero-phase cable 3), and other methods include: <2> The capacitance of the voltage dividing capacitor 4 is set to a value obtained by subtracting the capacitance of the zero-phase cable 3 from the capacitance of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is negligibly small, and then subtracting a predetermined value (for example, 1 to 5 times, 2 to 3 times, or the like, of the capacitance of the zero-phase cable 3) (i.e., the capacitance of the voltage dividing capacitor 4 = the capacitance of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is negligibly small - the capacitance of the zero-phase cable 3 - predetermined value); <3> The capacitance of the voltage dividing capacitor 4 is set to a value obtained by subtracting the capacitance of the zero-phase cable 3 from the capacitance of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is negligibly small, and then adding a predetermined value (for example, 0.1 to 1.0 times, or 1 to 3 times the capacitance of the zero-phase cable 3) (i.e., the capacitance of the voltage dividing capacitor 4 = the capacitance of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is negligibly small - the capacitance of the zero-phase cable 3 + predetermined value). <4> This may include setting the capacitance of the voltage dividing capacitor 4 to the value of the capacitance itself of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is small enough to be ignored (i.e., setting the capacitance of the voltage dividing capacitor 4 = the value of the capacitance of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is small enough to be ignored). In addition, in the present invention, "when the capacitance of the zero-phase cable 3 is negligibly small" may include, for example, when the length of the zero-phase cable 3 is 1 m or less, when the capacitance of a specified length of the zero-phase cable 3 is 0.001 μF or less, or when the capacitance of the zero-phase cable 3 falls within the error range of the capacitance of the voltage dividing capacitor 4.

[0039] In such a zero-phase voltage detector 1, for example, if the voltage value of the current flowing through the electric circuit D is the extra-high voltage "22,000 V," and the capacitance of each of the three voltage detecting capacitors 2 is "125 pF," then by subtracting the value "0.0105 μF (= capacitance of the zero-phase cable 3 "0.0036 μF" + predetermined value "0.0069 μF")" corresponding to the 10 m long zero-phase cable 3 from the theoretical capacitance value "0.2613 μF" of the voltage dividing capacitor 4, and setting the capacitance of the voltage dividing capacitor 4 to "0.2508 μF," a complete earth fault (one-phase complete earth fault) will occur on the electric circuit D side. When a ground fault occurs, the voltage (detection voltage V0) between one detection end 2A and the other detection end 2B of the detection capacitor 2 becomes "12702V" (calculation formula: 22000 ÷ √3), the divided voltage V2 between one voltage dividing end 4A and the other voltage dividing end 4B of the voltage dividing capacitor 4 becomes "approximately 18.99V" (calculation formula: (3 × 125pF ÷ 2508μF) × 12702V), and the voltage value of the zero-phase output current Z stepped down by the zero-phase transformer 5 becomes "approximately 0.9496V", and this zero-phase output current Z can be input to equipment such as the ground fault overvoltage relay unit 16, whose input voltage value is approximately 0.0 to 1.0V. Furthermore, if the voltage value of the current flowing through circuit D is the extra-high voltage "33000V," and the capacitance of each of the three voltage detector capacitors 2 is "83.333pF," then by subtracting the value "0.0105μF" (= capacitance of zero-phase cable 3 "0.0036μF" + predetermined value "0.0069μF") corresponding to the zero-phase cable 3, which is also 10m long, from the theoretical capacitance value "0.2613μF" of voltage divider capacitor 4, and setting the capacitance of voltage divider capacitor 4 to "0.2508μF," the same as the above "22000V," a complete earth fault will not occur on the side of circuit D. When this occurs, the detection voltage V0 of the detection capacitor 2 becomes "19052V" (calculation formula: 33000 ÷ √3), the divided voltage V2 of the voltage divider capacitor 4 becomes "approximately 18.99V" which is the same as "22000V" (calculation formula: (3 × 83.333pF ÷ 0.2508μF) × 19052V), and the voltage value of the zero-phase output current Z stepped down by the zero-phase transformer 5 also becomes "approximately 0.9496V", and this zero-phase output current Z can be input to equipment such as the earth fault overvoltage relay unit 16, whose input voltage value is the same as "22000V", which is approximately 0.0 to 1.0V. Therefore, if the capacitance of the voltage detector capacitor 2 is set to an appropriate value (125 pF, 83.333 pF, etc.) according to the extra-high voltage value (22,000 V, 33,000 V, etc.) of the current flowing through the electric circuit D, and the capacitance of the voltage divider capacitor 4 is set to a value (0.2508 μF, etc.) according to the zero-phase cable 3, it can be said that the voltage value of the zero-phase output current Z can be set to a value within a certain range (approximately 0.9496 V, etc.) suitable for equipment such as the earth fault overvoltage relay unit 16, regardless of the voltage value (22,000 V, 33,000 V, etc.) of the current flowing through the electric circuit D, thereby making it possible to eliminate the need to change equipment such as the earth fault overvoltage relay unit 16. In addition, if the voltage value of the current flowing through circuit D is "6600V" other than the extra-high voltage, the capacitance of each of the three voltage detector capacitors 2 is set to "250pF", and the capacitance of the zero-phase cable 3 can be ignored (for example, the capacitance of a 1m zero-phase cable 3 is 0.00036μF), then the capacitance of the voltage divider capacitor 4 (only the internal voltage divider capacitor 4a without external voltage divider capacitor 4b attached) can be set to "0.1568μF", and when a complete earth fault occurs on the side of circuit D, the voltage detector voltage V of voltage detector capacitor 2 will be 0 becomes "3810V" (calculation formula: 6600 ÷ √3), and the divided voltage V2 of the voltage dividing capacitor 4 becomes "approximately 18.22V", which is almost the same as "22000V" or "33000V" (calculation formula: (3 × 250pF ÷ 0.1568μF) × 3810V), and the voltage value of the zero-phase output current Z stepped down by the zero-phase transformer 5 is also "approximately 0.9112V", and this zero-phase output current Z can be input to equipment such as the earth fault overvoltage relay unit 16, which has an input voltage value of approximately 0.0 to 1.0V, the same as "22000V" or "33000V". Therefore, even if the voltage value of the current flowing through the electric circuit D is other than the extra-high voltage (6600V, etc.), by setting the capacitance of the voltage detector capacitor 2 to an appropriate value (250pF, etc.) according to that voltage value and setting the capacitance of the voltage divider capacitor 4 to a value (0.1568μF, etc.) according to the zero-phase cable 3, it can be said that regardless of the voltage value (6600V, etc.) of the current flowing through the electric circuit D, the voltage value of the zero-phase output current Z can be set to a certain range of value (approximately 0.9112V, etc.) suitable for equipment such as the earth fault overvoltage relay unit 16, making it possible to eliminate the need to change equipment such as the earth fault overvoltage relay unit 16.

[0040] <Zero-phase enclosure 6, etc.> 1 and 2, the zero-phase-sequence housing 6 is a housing that houses at least the above-mentioned zero-phase-sequence transformer 5. As mentioned above, the zero-phase-sequence transformer 5 can also be said to be a zero-phase-sequence converter, and therefore the zero-phase-sequence housing 6 can also be said to be a zero-phase-sequence conversion housing. The zero-phase casing 6 may incorporate the internal voltage dividing capacitor 4a described above, and may also be provided with an N terminal which is one voltage dividing end 4A of the voltage dividing capacitor 4 described above, an E terminal which is the other voltage dividing end 4B of the voltage dividing capacitor 4, or the Y1 terminal and Y2 terminal of the zero-phase casing 6. Additionally, the zero-phase casing 6 may incorporate a test capacitor 1a, which will be described later, or may be provided with a test terminal.

[0041] The test capacitor 1a is a capacitor built into the above-mentioned zero-phase casing 6, and is a capacitor used when testing the zero-phase voltage detector 1. The test capacitor 1a has its test end 1aA connected to the other cable end 3B of the above-mentioned zero-phase cable 3, which can also be said to be connected to one voltage dividing end 4A of the voltage dividing capacitor 4 (or one internal voltage dividing end 4aA of the internal voltage dividing capacitor 4a). The other test end 1aB of the test capacitor 1a is connected to a test terminal, which will be described later. Therefore, it can be said that the test capacitor 1a is connected in series with the voltage dividing capacitor 4 (or the internal voltage dividing capacitor 4a). The capacitance of such a test capacitor 1a is not particularly limited, but may be, for example, 1 pF to 10,000 pF, preferably 10 pF to 5,000 pF, and more preferably 50 pF to 1,000 pF (such as 390 pF or 750 pF). The capacitance of the test capacitor 1a may be the capacitance of a single capacitor or the total capacitance of multiple capacitors connected in parallel. If it is the total capacitance of multiple capacitors, the capacitance of each capacitor may be approximately the same value (e.g., 390 pF x 2) or may be different values.

[0042] The test terminal is also a terminal used when testing the zero-phase voltage detector 1, and as described above, is connected to the other test end 1aB of the test capacitor 1a, and is also called a T terminal. When testing the zero-phase voltage detector 1, a voltage may be applied to the T terminal (test terminal) on the zero-phase casing 6 and the E terminal (the other voltage-dividing end 4B of the voltage-dividing capacitor 4 (or the other internal voltage-dividing end 4aB of the internal voltage-dividing capacitor 4a)). Alternatively, if the zero-phase voltage detector 1 does not have a T terminal (test terminal), a voltage may be applied to the side where all three phases (U phase, V phase, W phase) on the electric circuit D side are short-circuited, and to the E terminal (the other voltage-dividing end 4B of the voltage-dividing capacitor 4 (or the other internal voltage-dividing end 4aB of the internal voltage-dividing capacitor 4a)).

[0043] <Power System 10> As shown in FIG. 2, the power system 10 according to the present invention includes the above-mentioned zero-phase voltage detector 1, etc., as well as a power generation unit 11, a conversion unit 12, a system transformer 13, and a grid connection unit 14, which will be described later. The grid connection unit 14 includes a high-voltage circuit 15H, a zero-phase output circuit 15Z, an earth fault overvoltage relay unit 16, a capacitor output circuit 15C, and a capacitor device 17, which will be described later. The power system 10 may include, within the grid connection unit 14, an instrument transformer 20, a sensor current transformer 21, a transformer output electric circuit 15S, a sensor output electric circuit 15B, and a reverse power relay unit 22, which will be described later. The power system 10 may include a calculation unit 23 and a device housing 24, which will be described later, in the grid connection unit 14.

[0044] Furthermore, the power system 10 may include a power breaker 31, loads 32 (power loads 32a and lighting loads 32b), a load transformer 33, and a load breaker 34, which will be described later. Additionally, the power system 10 may have a voltage and current transformer (VCT) 41a in the electric circuit (high-voltage circuit 15H) between the system connection unit 14 and the system K, and may also have a power purchase watt-hour meter, a power sale watt-hour meter, pole air switches (PAS), and a protective relay device (Storage Over Current Ground (SOG)) attached to the pole air switches, all of which are not shown. The pole air switches may also have a separate built-in voltage transformer, zero-phase sequence voltage detector, and lightning arrester. These commerce transformer 41a, electricity purchasing watt-hour meter, electricity selling watt-hour meter, pole-mounted air switch, and protective relay device may be included in the system on the system K side (electric power company side) described later.

[0045] <Power Generation Section 11> As shown in FIG. 2, the power generation unit 11 is a 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 atmospheric heat 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). Alternatively, the power generating unit 11 may generate power using ocean temperature difference, wave power, tidal currents (ocean currents), or tides.

[0046] The number of power generation units 11 in one power system 10 is not particularly limited, and may be, for example, one or more. The power generation capacity (capacity) of the power generation unit 11 is not particularly limited, but 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 11 that generates solar power.

[0047] The solar power generation unit 11 includes a solar cell 11a. In addition, the solar power generation unit 11 may include a pyranometer that measures solar radiation intensity, a current collection unit that collects DC current from the solar cells 11a, a connection box, etc., and sends it to the conversion unit 12 described below. The solar power generation unit 11 may include a plurality of solar cells 11a, and these solar cells 11a may be connected in series to form a solar cell string. The solar power generation unit 11 may have a connection box in which a plurality of solar cell strings are connected in parallel, and there may be a plurality of such connection boxes.

[0048] <Solar cell 11a> As shown in Figure 2, each solar cell 11a generates DC power between its positive and negative poles when exposed to light. Solar cells 11a are usually in the form of a panel, and the amount of power they generate varies depending on the angle at which they are installed. The solar cell 11a may be installed at a predetermined angle relative to the installation location via a stand (not shown) or the like, and in this case, the area under the stand may be used as a lawn growing area or cultivated land for agricultural crops. Furthermore, among the multiple solar cells 11a, the positive terminal of one solar cell 11a is connected to the negative terminal of another solar cell 11a, and the positive terminal of another solar cell 11a is connected to the negative terminal of yet another solar cell 11a, and this is repeated to connect multiple solar cells 11a in series to form a solar cell string.

[0049] In this way, the voltage between the positive and negative poles of the entire solar cell string, in which multiple solar cells 11a are connected in series, is the sum of the DC voltages generated by each solar cell 11a, and varies depending on the weather, time of day, etc. The power output from the power output terminal of the solar cell string is the sum of the power of each solar cell 11a, and may be between 500W and 6000W. The above-mentioned multiple solar cell strings are connected in parallel to one junction box, so 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.

[0050] <Conversion unit 12> As shown in FIG. 2, the conversion unit 12 is a part that converts the DC current or AC current from the power generation unit 11 described above into a low-voltage AC current L. The conversion unit 12 may include an inverter that converts the direct current from the solar cell 11a into alternating current, and may also include 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 12 is also called a power conditioner (Pawakon). The number of conversion units 12 in one power system 10 is not particularly limited, and may be, for example, a plurality (for example, four or five) or just one.

[0051] The conversion power (capacity) that can be converted by the conversion unit 12 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 12 may be smaller than the power generation power of the above-mentioned solar power generation unit 11 (in other words, the power generation power may be greater than the conversion power), and in this case, it can be said that the solar cell 11a is overloaded with respect to the conversion unit 12. In addition, the conversion unit 12 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.

[0052] <System Transformer 13> As shown in Fig. 2, the system transformer 13 is a device that transforms (boosts) the low-voltage AC current L from the conversion unit 12 described above into a higher-voltage AC current H, and is what is known as a transformer. Note that "transformer" is an abbreviation for "transformer." Furthermore, since the system transformer 13 transforms the current from the power generation unit 11 via the conversion unit 12, it can also be said to be a power generation transformer. The number of system transformers 13 in one power system 10 is not particularly limited, and may be, for example, a plurality (for example, two) or one. In addition, in the power system 10 described below, the system transformer 13 can also be said to be connected between the system K (high voltage line 15H side) and the conversion unit 12 (low voltage line 15L side). The capacity (unit: VA, continuous rating) of the system transformer 13 is not particularly limited, but 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.).

[0053] The configuration of the system transformer 13 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, the system transformer 13 will be primarily described as being a two-winding transformer. The system transformer 13, which is a two-winding transformer, may have, for example, a primary side on the high-voltage circuit 15H side and a secondary side on the low-voltage circuit 15L 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 15H side, may be 5000V or more and 40000V or less, preferably 5500V or more and 30000V or less, and more preferably 6000V or more and 25000V or less (6600V or 22000V, etc.), and the voltage of the secondary side, which is the low-voltage circuit 15L 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 (210V, 105V to 210V, etc.).

[0054] There are no particular restrictions on the wiring method for the primary and secondary sides of the system transformer 13, but for example, the primary side on the high-voltage circuit 15H side may be star-connected (Y-connected) and the secondary side on the low-voltage circuit 15L side may be triangular-connected (Δ-connected) (i.e., Y-Δ connection), or the order of the primary and secondary sides may be YY connection, Δ-Y connection, or Δ-Δ connection. The system transformer 13 may be an oil-immersed 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.

[0055] <Grid connection part 14> As shown in FIG. 2, the system connection unit 14 is a part that connects the above-mentioned system transformer 13 to the system K. As described above, the system connection unit 14 includes a high-voltage circuit 15H, a zero-phase voltage detector 1, a zero-phase output circuit 15Z, an earth fault overvoltage relay unit 16, a capacitor output circuit 15C, a capacitor device 17, and the like, which will be described later. As described above, the system connection unit 14 may have an instrument transformer 20, a sensor current transformer 21, a transformer output circuit 15S, a sensor output circuit 15B, and a reverse power relay unit 22, which will be described later, and may also have a calculation unit 23 and an apparatus housing 24, which will be described later. The system connection unit 14 may include a vacuum circuit breaker 14a, a disconnector 14b, and a load switch 14c, which will be described later, and may also include an overcurrent relay 14d and an instrument current transformer 21a, which will be described later.

[0056] <Vacuum circuit breaker 14a, disconnector 14b, load switch 14c, overcurrent relay 14d> As shown in FIG. 2, the vacuum circuit breaker (VCB) 14a is provided in a high-voltage circuit 15H (described later), and is a device that opens and closes (three-phase, three-wire collectively) the high-voltage circuit 15H when a high-voltage AC current H (load current) is flowing, and extinguishes the arc within the vacuum valve. The vacuum circuit breaker 14a may be provided, for example, between a voltage transformer 20 (a branch point of the transformer branch electric circuit 15S') and the sensor current transformer 21 (or the instrument current transformer 21a), which will be described later. The vacuum circuit breaker 14a may also be of an electric spring operation (capacitor trip) type. As shown in Fig. 2, the disconnecting switch (DS) 14b is provided in the high-voltage circuit 15H (described later) and is a device that opens and closes the high-voltage circuit 15H when high-voltage AC current H (load current) is not flowing. The disconnecting switch 14b does not have the function of interrupting the current, and opens and closes the disconnecting switch 14b after the current is interrupted by another circuit breaker. The disconnecting switch 14b may be provided, for example, between the potential transformer 20 (the branch point of the transformer branch circuit 15S') and the system K (or the utility transformer 41a). The disconnecting switch 14b may also be opened and closed by operating a hook.

[0057] As shown in FIG. 2 , a load break switch (LBS) 14c may be provided in a high-voltage circuit 15H (described later). It is a device that switches the high-voltage circuit 15H (three-phase, three-wire circuit) when high-voltage AC current H (load current) is flowing. It is also referred to as a high-voltage AC load break switch. The load break switch 14c may have power fuses (four or more). The load break switch 14c may also be equipped with an insulating barrier, or the load break switch 14c may be opened or closed by a hook operation. The number of load break switches 14c in one power system 10 is not particularly limited, and may be, for example, multiple (e.g., two), one, or the same number as the number of transformers (including the system transformer (power generating transformer) 13 described above and the load transformer 33 described later). Hereinafter, the number of load break switches 14c will be mainly described as two. The two load switches 14c may be provided, for example, in the high-voltage circuit 15H branching between the sensor current transformer 21 (or the instrument current transformer 21a) and each transformer (the power generation system transformer 13, the load transformer 33). 2, when the grid connection unit 14 has an instrument current transformer 21a, the overcurrent relay (OCR) 14d is connected to the instrument current transformer 21a via a current transformer output circuit 15R (described later), receives the transformed output current R (lower-voltage transformed output current R corresponding to the low-voltage AC current L flowing in the high-voltage circuit 15H) output from the instrument current transformer 21a, and performs a predetermined operation (e.g., outputs a stop signal to stop the conversion of the above-mentioned conversion unit 12) when the transformed output current R exceeds a certain value (value of operating current) for a certain time (e.g., an operating time of about 1 second). In one power system 10, the number of overcurrent relays 14d and the number of above-mentioned instrument current transformers 21a are the same, and the number may be one or more. The power supply of the overcurrent relay 14d is connected to an uninterruptible power supply (not shown) or the like, and is input from the uninterruptible power supply or the like.

[0058] <High voltage circuit 15H, low voltage circuit 15L> As shown in Fig. 2, high-voltage circuit 15H is an electric circuit that connects the above-mentioned system transformer 13 and the grid K and carries high-voltage AC current H, and can also be considered a high-voltage cable. Note that high-voltage circuit 15H may branch midway (for example, between sensor current transformer 21 (or instrument current transformer 21a) and system transformer 13) to system transformer 13 and load transformer 33 (described later), and these branched electric circuits also carry high-voltage AC current H, and therefore can also be considered high-voltage circuits 15H. High-voltage circuit 15H may be arranged in a set of three wires in the case of a three-phase three-wire system (3φ3W) or a single-phase three-wire system (1φ3W), or in a set of two wires in the case of a single-phase two-wire system (1φ2W), and multiple wires may be arranged in a set depending on the power distribution system (power transmission system). 2, the low-voltage circuit 15L is an electrical circuit that connects the above-described conversion unit 12 and system transformer 13 and carries low-voltage AC current L, and can also be considered a low-voltage cable. Note that the low-voltage circuit 15L may also branch to each conversion unit 12 along the way (for example, between the system transformer 13 and the conversion unit 12) depending on the number of conversion units 12, and these branched electrical circuits also carry low-voltage AC current L, and therefore can also be considered low-voltage circuits 15L. In addition, the electrical circuit between the system transformer 13 and a load 32 (power load 32a) described below and the electrical circuit between a load transformer 33 described below and a load 32 (lighting load 32b) also carry low-voltage AC current L, and therefore can also be considered low-voltage circuits 15L. The low-voltage circuit 15L may also consist of multiple cables in a set depending on the power distribution method (power transmission method), such as a set of three cables for three-phase three-wire (3φ3W) or single-phase three-wire (1φ3W), or a set of two cables for single-phase two-wire (1φ2W).

[0059] <Zero-phase voltage detector 1, etc., installed in high-voltage power line 15H> As shown in Figures 1 and 2, in the power system 10, the zero-phase voltage detector 1 is provided in the above-mentioned high-voltage circuit 15H, and can be said to be an instrument that detects whether a ground fault (such as a complete single-wire ground fault in a three-phase, three-wire system) has occurred on the high-voltage circuit 15H side or any other system (including the system K side) in the power system 10, and whether a zero-phase voltage has occurred on the high-voltage circuit 15H side. The circuit between the zero-phase voltage detector 1 and the earth fault overvoltage relay unit 16 described later is the zero-phase output circuit 15Z, and the zero-phase output circuit 15Z may be a set of three lines depending on the power distribution method (power transmission method), such as a set of three lines in the case of a three-phase three-wire (3φ3W) system. In the zero-phase output circuit 15Z, when the zero-phase voltage detector 1 detects a zero-phase voltage, a zero-phase output current Z of a lower voltage (for example, approximately 1 V, approximately 0.0 to 1.0 V, approximately 6 to 9 V, etc.) corresponding to the zero-phase voltage generated in the power system 10, etc., is output from the zero-phase transformer 5 of the zero-phase voltage detector 1 and flows through the zero-phase output circuit 15Z. In addition, "the zero-phase voltage detector 1, etc. is provided in the high-voltage circuit 15H" means that the zero-phase voltage detector 1, etc. is connected to a zero-phase branch circuit 15Z' that branches off from the high-voltage circuit 15H described below. Since this zero-phase branch circuit 15Z' is three-phase three-wire (3φ3W), there are three cables in one set, and multiple cables may be used in one set depending on the power distribution method (power transmission method). The zero-phase branch electric circuit 15Z' may branch off from anywhere in the high-voltage power circuit 15H, for example, it may branch off from between the load switch 14c and the system transformer 13 in the high-voltage power circuit 15H.

[0060] <Earth fault overvoltage relay unit 16> As shown in Figures 1 and 2, the earth fault overvoltage relay unit 16 is connected to the zero-phase voltage detector 1 via the above-mentioned zero-phase output circuit 15Z, and is a part that detects an earth fault overvoltage state based on the zero-phase output current Z. When this earth fault overvoltage relay unit 16 detects an earth fault overvoltage state, it may output a signal to stop the conversion of the above-mentioned conversion unit 12, etc. Here, "detecting an earth fault overvoltage state" means that, as described above, an earth fault occurs somewhere in the power system 10, etc., causing a zero-phase voltage on the high-voltage circuit 15H 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 15H side, etc.) output from the zero-phase voltage detector 1 is input to the earth fault overvoltage relay unit 16, 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 equal to or greater than a predetermined value" does not necessarily mean that the zero-phase output current Z becomes equal to or greater than a threshold value in the strict sense; depending on the resolution and settings of the earth fault overvoltage relay unit 16, it may also mean that the zero-phase output current Z becomes "equal to or greater than 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 16, 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 12 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.

[0061] The output signal from the earth fault overvoltage relay unit 16 may be input directly to the conversion unit 12, or alternatively, may be input to a control device (not shown) of the conversion unit 12, which will be described later, or to the calculation unit 23. When the output signal from the earth fault overvoltage relay unit 16 is input directly to the conversion unit 12, the earth fault overvoltage relay unit 16 can also be said to be a control device. In one power system 10, the number of earth fault overvoltage relay units 16 is the same as the number of the above-described zero-phase sequence voltage detectors 1, and the number may be one or more. The power supply for the earth fault overvoltage relay unit 16 is connected to a capacitor device 17 (described later), an instrument transformer 20, and an uninterruptible power supply (not shown), and is input from the capacitor device 17. The earth fault overvoltage relay unit 16 can also be said to be an overvoltage ground relay (OVGR).

[0062] <Capacitor device 17> 2, capacitor device 17 is a device that charges and discharges electricity (electrical energy), and is connected to ground fault overvoltage relay unit 16 via capacitor output circuit 15C that supplies power supply power (control power supply) to ground fault overvoltage relay unit 16. Capacitor device 17 can also be called a capacitor device. When the power system 10 and the like are not experiencing a power outage (when there is no power outage), the capacitor device 17 is charged with electricity from the potential transformer 20 via a capacitor input circuit 15C' branching off from a transformer output circuit 15S through which a transformer output current S from the potential transformer 20 described below flows. If the transformer output circuit 15S is a three-phase, three-wire circuit, the current may be input to the capacitor device 17 as a single-phase, two-wire capacitor input circuit 15C' via a voltmeter changeover switch (not shown). When a power outage occurs, the capacitor device 17 discharges the electricity it has stored, causing a capacitor output current C (140V, 154V, etc.) to flow through the capacitor output circuit 15C, and supplying power from the power source to the earth fault overvoltage relay unit 16. As a result, the capacitor device 17 supplies power source power to the earth fault overvoltage relay unit 16 via the capacitor output circuit 15C when a power outage occurs in a system such as the high-voltage circuit 15H side (including the system K side) in the power system 10.

[0063] The capacitor device 17 may have a charging indicator lamp that lights up when the capacitor device 17 is charged (fully charged), and a discharge switch (such as a switch that is pressed and held until the charging indicator lamp goes out) that is used to forcibly discharge the capacitor device 17 when the capacitor device 17 is installed or removed. The capacitor device 17 has a capacitor as an electrical component that charges and discharges electricity, and may also have a fuse (e.g., φ5.2×20 mm, 5 A) provided in the circuit immediately after the transformer output current S is input via the capacitor input circuit 15C′, a rectifier that rectifies the transformer output current S, which is AC and input via the capacitor input circuit 15C′, 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 capacitor device 17 has an input voltage of 10V to 500V, preferably 40V to 400V, and more preferably 80V to 300V (100V, 110V, 200V, 220V, etc.), a charging voltage (which can also be called the voltage of the discharged capacitor output current C) of 10V to 600V, preferably 50V to 500V, and more preferably 100V to 400V (140V, 154V, 280V, 308V, etc.), and a consumption current (which can also be called the current of the discharged capacitor output current C) of 1mA to 100mA, preferably 3mA to 70mA, and more preferably 5mA to 40mA. The current is below 8 mA (e.g., 8 mA or 20 mA), the capacitor capacity (capacitor capacity as an electronic component) is 100 μF to 5000 μF, preferably 200 μF to 4000 μF, and more preferably 300 μF to 3000 μF (e.g., 470 μF or 1500 μF), the charging time is 0.01 to 0.50 seconds, preferably 0.05 to 0.40 seconds, and more preferably 0.10 to 0.30 seconds (e.g., 0.2 seconds or less), and the discharge time may be 0.1 to 30.0 seconds, preferably 0.5 to 20.0 seconds, and more preferably 1.0 to 10.0 seconds (e.g., about 3 seconds, about 6 to 7 seconds). Note that this discharge time may be longer (or at least two or three times longer) than the predetermined time in the above-mentioned ground fault overvoltage relay unit 16 or the predetermined time in the below-described reverse power relay unit 22.

[0064] <Instrument transformer 20, etc.> As shown in Fig. 2, a voltage transformer (VT) 10 is provided in the above-mentioned high-voltage circuit 15H, and is a device that transforms (steps down) the high-voltage AC current H flowing through the high-voltage circuit 15H into a lower-voltage transformed output current S. Note that there may be not only one voltage transformer 20 in one power system 10, but also multiple (two, for example) voltage transformers 20. The electric path between the potential transformer 20 and the reverse power relay unit 22 (or the calculation unit 23) described later is a transformer output electric path 15S through which the transformer output current S flows, and the transformer output electric path 15S 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 15S is a three-phase three-wire system, as described above, it may be input to the reverse power relay unit 22 or the like as a single-phase two-wire system via a voltmeter changeover switch (not shown). The transformer output circuit 15S receives (at least a portion of) a transformer output current S of a lower voltage (e.g., 110V) corresponding to the voltage of the high-voltage AC current H flowing through the high-voltage circuit 15H, which is output from the instrument transformer 20 and flows through the transformer output circuit 15S.

[0065] The capacity of the potential transformer 20 is not particularly limited, but may be, for example, 10 VA to 500 VA, preferably 20 VA to 300 VA, and more preferably 40 VA to 200 VA (eg, 100 VA). The potential transformer 20 is not limited to a specific configuration and may be a transformer with three or more windings, but will be mainly described as a two-winding transformer. The voltage transformer 20, which is a two-winding transformer, may have, for example, a primary side on the high-voltage circuit 15H side and a secondary side on the reverse power relay unit 22 or the like side. In this case, there are no particular restrictions on the specific values, but for example, the voltage on the primary side, which is on the high-voltage circuit 15H side, may be 5000V or more and 40000V or less, preferably 5500V or more and 30000V or less, and more preferably 6000V or more and 25000V or less (6600V or 22000V, etc.), and the voltage on the secondary side, which is on the reverse power relay unit 22 side, may be 10V or more and 600V or less, preferably 20V or more and 400V or less, and more preferably 50V or more and 300V or less (110V, etc.). The potential transformer 20 may have a power fuse (PF) on the primary side and / or the secondary side.

[0066] In addition, "the voltage transformer 20 is provided in the high-voltage circuit 15H" means that the voltage transformer 20 is connected to a transformer branch circuit 15S' that branches off from the high-voltage circuit 15H, and this transformer branch circuit 15S' may be a set of three wires in the case of a three-phase three-wire (3φ3W) system, for example, or multiple wires may be used in one set depending on the power distribution method (power transmission method). The transformer branch electric circuit 15S' may branch off from anywhere in the high-voltage electric circuit 15H, for example, it may branch off from between the vacuum circuit breaker 14a and the disconnecting switch 14b in the high-voltage electric circuit 15H.

[0067] <Sensor current transformer 21> 2, the sensor current transformer 21 is provided in a high-voltage circuit 15H (described later) and is a device that outputs a smaller sensor output current B from the high-voltage AC current H flowing through the high-voltage circuit 15H. Note that there may be not only one sensor current transformer 21 but also multiple (two, for example) sensor current transformers 21 in one power system 10. The electrical path from sensor current transformer 21 to reverse power relay unit 22 (or calculation unit 23), which will be described later, is sensor output electrical path 15B through which sensor output current B flows, and sensor output electrical path 15B may be a set of two electrical paths in the case of single-phase two-wire (1φ2W) or the like, or a set of three electrical paths in the case of three-phase three-wire (3φ3W) or the like, or may be a set of multiple electrical paths depending on the power distribution system (power transmission system). Note that when sensor output electrical path 15B is a three-phase three-wire system, as described above, it may be input to reverse power relay unit 22 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 (for example, 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 15H, is output from the sensor current transformer 21 and flows through the sensor output circuit 15B.

[0068] The number of times (turns) that the winding of the sensor current transformer 21 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 15H (and the current-transformed output circuit 15R described later) can be said to be one turn compared to the number of turns of the sensor current transformer 21, the current transformation ratio between the primary side (the side of the high-voltage circuit 15H, etc.) and the secondary side (output side) of the sensor current transformer 21 is 1: the number of turns of the sensor current transformer 21. The value of this current transformation ratio is not particularly limited, but 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 21 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 21 may be 10 to 20 times the maximum value of the rated range of current described above, and may be, for example, 100 kA or less, preferably 80 kA or less, and more preferably 60 kA or less (such as 40 kA).

[0069] Incidentally, "the sensor current transformer 21 is provided in the high-voltage circuit 15H" means that the sensor current transformer 21 is not only provided directly in the high-voltage circuit 15H (for example, an open / close type (also called a split type, such as a fluxgate type or a Hall element type) sensor current transformer 21 that can be attached to two of the three-phase three-wire high-voltage circuit (high-voltage cable) 15H without splitting each high-voltage cable 15H and is opened and closed by itself, but also that the sensor current transformer 21 is provided in the current transformer output circuit 15R (in other words, the secondary side of the instrument current transformer 21a) that passes the transformed output current R from the instrument current transformer 21a described later, and this current transformer output circuit 15R may be a single-phase two-wire (1φ2W) or the like. Incidentally, the provision of the sensor current transformer 21 on the current transformer output circuit 15R may mean, for example, that the sensor current transformer 21 is an open / close type that can be attached to each of the single-phase two-wire current transformer output circuits 15R without opening or closing each current transformer output circuit 15R, and that the sensor current transformer 21 is retrofitted by opening and closing itself. The instrument current transformer 21a will be described below.

[0070] <Instrument current transformer 21a> As shown in FIG. 2, the current transformer (CT) 21a is provided in the high-voltage circuit 15H described later, and is a device that transforms the high-voltage AC current H flowing through the high-voltage circuit 15H into a smaller transformed output current R. As described above, the electric circuit between the instrument current transformer 21a and the above-mentioned overcurrent relay 14d is the current transformer output electric circuit 15R through which the current transformer output current R flows, and the current transformer output electric circuit 15R may also be a set of two electric circuits in the case of a single-phase two-wire (1φ2W) system or the like, or a set of three electric circuits in the case of a three-phase three-wire (3φ3W) system or the like, and may be a set of multiple electric circuits depending on the power distribution system (power transmission system). Note that when the current transformer output electric circuit 15R is a three-phase three-wire system, it may be input to the overcurrent relay 14d as a single-phase two-wire system via an ammeter changeover switch (not shown) as described above. The current transformer output circuit 15R outputs a current transformer output current R, which is a smaller current (for example, approximately 10 A) corresponding to the current of the high-voltage AC current H flowing in the high-voltage circuit 15H, from the sensor current transformer 21 and flows into the sensor output circuit 15B.

[0071] The number of times (turns) that the winding of the instrument current transformer 21a 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 15H can be said to be one compared to the number of turns of the instrument current transformer 21a, the current transformation ratio between the primary side (the high-voltage circuit 15H side) and the secondary side (output side) of the instrument current transformer 21a is 1:number of turns of the instrument current transformer 21a. The value of this current transformation ratio is not particularly limited, but 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 current range of the instrument current transformer 21a is not particularly limited, but may be, for example, 15 A to 1800 A, preferably 20 A to 1650 A, and more preferably 25 A to 1500 A (eg, 60 A). Furthermore, the maximum value of the range of the current actually flowing through the instrument current transformer 21a 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).

[0072] Incidentally, "the instrument current transformer 21a is provided in the high-voltage circuit 15H" means that the instrument current transformer 21a is provided directly in the high-voltage circuit 15H, and for example, it may be provided from the beginning by splitting each high-voltage cable 15H for two of the three-phase three-wire high-voltage circuit (high-voltage cable) 15H, or it may be provided later by opening and closing the instrument current transformer 21a itself, which is an open / close type (fluxgate type, Hall element type, etc.) that can be installed without splitting each high-voltage cable 15H. The instrument current transformer 21a may be provided anywhere in the high-voltage circuit 15H, for example, it may be provided between the vacuum circuit breaker 14a and the load switch 14c in the high-voltage circuit 15H.

[0073] <Reverse power relay unit 22> As shown in FIG. 2, the reverse power relay unit 22 is connected to the potential transformer 20 via the above-mentioned transformer output circuit 15S, and at the same time is connected to the sensor current transformer 21 (or connected to the calculation unit 23) via the above-mentioned sensor output circuit 15B, 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 22 detects a reverse power generation state, it may output a signal to stop the conversion of the above-mentioned conversion unit 12, for example. Here, "detecting a reverse power generation state" means that, as described above, it is determined that reverse power (power flowing backward from the high-voltage power line 15H side to the system K) calculated by the calculation unit 23 described later based on the transformer output current S and the sensor output current B has occurred, and that the reverse power has reached a predetermined value (threshold value) or greater. Furthermore, "the reverse power is equal to or greater than a predetermined value" does not necessarily mean that the reverse power is strictly equal to or greater than a threshold value, but depending on the resolution and settings of the reverse power relay unit 22, it may also mean that the reverse power is "equal to or greater than 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 22, and may be, for example, the sum of the threshold value and 1 mA, 1 μA, 1 nA, etc. This includes not only the case where a signal is output to the conversion unit 12 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 reaches a predetermined value or more.

[0074] The output signal from the reverse power relay unit 22 may be input directly to the conversion unit 12, or alternatively, may be input to a control device of the conversion unit 12 (described later) or to the calculation unit 23. When the output signal from the reverse power relay unit 22 is input directly to the conversion unit 12, the reverse power relay unit 22 can also be said to be a control device. In one power system 10, the number of reverse power relay units 22 and the number of the above-mentioned instrument transformers 20 and sensor current transformers 21 may be the same or different, and the number may be one or more. The power supply for the reverse power relay unit 22 is also connected to a capacitor device 17, which will be described later, an instrument transformer 20, an uninterruptible power supply (not shown), and the like, and can be said to receive power from the capacitor device 17, etc. The reverse power relay unit 22 can also be said to be a reverse power relay (RPR).

[0075] <Calculation unit 23> As shown in FIG. 2, the calculation unit 23 is a part that calculates at least the power in the high-voltage circuit 15H based on the transformer output current S and the sensor output current B described above. The calculation unit 23 is not particularly limited as long as it can calculate at least the power in the high-voltage circuit 15H, but it may be, for example, an electronic or mechanical type, a three-phase type (a method of measuring two phases out of three phases and three wires), or a single-phase type. Hereinafter, the calculation unit 23 will be described as being mainly electronic and three-phase. The calculation unit 23 may calculate, in addition to the power in the high-voltage circuit 15H, for example, at least one of the current, voltage, power factor, and amount of power in the high-voltage circuit 15H based on the transformer output current S and the sensor output current B. The calculation of the power and the like in the calculation unit 23 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 16 detects an earth fault overvoltage state or when the reverse power relay unit 22 detects a reverse power generation state, the calculation unit 23 may collectively stop the conversion of the conversion unit 12 via a signal to the conversion unit 12, and in this case, the calculation unit 23 can also be said to be a control device. Furthermore, the electric circuits between the above-mentioned voltage transformer 20 or sensor current transformer 21 and reverse power relay unit 22 may be connected via calculation unit 23, and even in this connection via calculation unit 23, it can be said that the voltage transformer 20 and reverse power relay unit 22 are connected by transformer output electric circuit 15S, and the sensor current transformer 21 and reverse power relay unit 22 are connected by sensor output electric circuit 15B. In this connection via calculation unit 23, the transformed AC current S from the voltage transformer 20 and the sensor output current B from sensor current transformer 21 are first input to calculation unit 23, which calculates the power (reverse power) in the high-voltage circuit 15H, and the calculated reverse power is input from calculation unit 23 to reverse power relay unit 22.

[0076] <Device enclosure 24> As shown in FIG. 2, the device housing 24 is a housing in which the above-described ground fault overvoltage relay unit 16, reverse power relay unit 22, and calculation unit 23 are provided (built-in). There are no particular limitations on the shape, size, configuration, etc. of the device housing 24 as long as it incorporates the earth fault overvoltage relay unit 16, the reverse power relay unit 22, and the calculation unit 23, but for example, the shape may be approximately cubic or approximately rectangular. The device housing 24 may have a display unit that displays the power value calculated by the calculation unit 23 described above, and there are no particular limitations on the shape, size, position, configuration, etc. of this display unit, 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 23, but also the integrated power (i.e., the amount of power) of that power, or numbers indicating the mode or state.

[0077] The device housing 24 may have an operation unit, and there are no particular limitations on the configuration, role, position, etc. of this operation unit, but for example, a plurality of buttons may be provided. The operation unit may serve, for example, as a button to turn the display unit on and off (display button), a reset button to reset the composite relay device 30 described below, buttons to select a mode or state (such as a "+" button or a "-" button), or a set button to confirm (set) the selected mode, etc. The position of such an operation unit may also be provided, for example, on the front surface of the device housing 24, below the display unit described above. The device housing 24 may have a terminal portion (terminal block), and there are no particular limitations on the number or position of these terminal portions. For example, one device housing 24 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 16 and the reverse power relay unit 22, into a single device housing 24 can also be said to be a ``composite relay device (composite relay) 30.'' In the case of such a combined relay device 30, it can be said that the earth fault overvoltage relay unit 16, the reverse power relay unit 22, and the calculation unit 23 are connected to each other within the device housing 24, and therefore if the zero-phase output circuit 15Z from the zero-phase voltage detector 1, the capacitor output circuit 15C from the capacitor device 17, the transformer output circuit 15S from the voltage transformer 20, and the sensor output circuit 15B from the sensor current transformer 21 are connected to the combined relay device 30, it can be said that the zero-phase output circuit 15Z from the zero-phase voltage detector 1 and the capacitor output circuit 15C from the capacitor device 17 are connected to the earth fault overvoltage relay unit 16, and the transformer output circuit 15S from the voltage transformer 20 and the sensor output circuit 15B from the sensor current transformer 21 are connected to the reverse power relay unit 22. Furthermore, in the case of this composite relay 30, the power supply units of the earth fault overvoltage relay unit 16, the reverse power relay unit 22, and the calculation unit 23 may be combined into one, and this power supply unit has a power supply range that corresponds to the voltage of the capacitor output current C input to the composite relay 30. For example, if the capacitor output current C is DC, it may correspond to DC 80V or more and 143V or less, or DC 20V or more and 56V or less, or if the capacitor output current C is AC, it may correspond to AC 85V or more and 264V or less.

[0078] <Power generation circuit breaker 31, load 32, load transformer 33, load circuit breaker 34> As shown in FIG. 2 , the power generation circuit breaker 31 is a device capable of interrupting the low-voltage AC current L from the converter unit 12. In other words, the power generation circuit breaker 31 is a device provided in the low-voltage circuit 15L described below and capable of interrupting the low-voltage circuit 15L, and can also be considered a low-voltage circuit breaker. The power generation circuit breaker 31 may be a molded case circuit breaker (MCCB) or an earth leakage circuit breaker (ELCB). There may be one or more power generation circuit breakers 31 in each power system 10. For example, as described above, if the low-voltage circuit 15L branches between the system transformer 13 and the converter unit 12 to each of the converter units 12 according to the number of converter units 12, one power generation circuit breaker 31 may be provided between the branching point and the system transformer 13, and one may be provided between the branching point and each of the converter units 12. 2, the load 32 is a device that consumes power from the power generation unit 11 via the conversion unit 12, or power from the grid K via the grid connection unit 14, the system transformer 13, etc. The load 32 may have any configuration, and may be, for example, an industrial motor (power load) 32a in a factory or the like, a light (electric lighting load) 32b in a factory or the like, a lighting distribution board connected to multiple lights 32b, or an air conditioner, fluorescent light, home appliance, vehicle such as an electric car or gasoline car, or device in the vehicle in addition to the above.

[0079] As shown in FIG. 2, the load transformer 33 is a device that transforms (steps down) the power from the system K and the power generation unit 11, and is a so-called transformer. The term "transformer" is an abbreviation for "transformer." The capacity of the load transformer 33 may be the same as that of the system transformer 13 described above, and the configuration of the load transformer 33 may be a two-winding transformer, etc. The primary side of the load transformer 33 can also be said to be the high-voltage circuit 15H side, and its secondary side can be the low-voltage side. In this case, the specific values ​​are not particularly limited, but for example, the voltage of the primary side, which is the high-voltage circuit 15H side, can be the same as that of the system transformer 13 described above, and the voltage of the secondary side, which is the low-voltage side, can be 10 V or more and 1000 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 (e.g., 105 V to 210 V). There are no particular restrictions on the connection method of the primary and secondary sides of the load transformer 33, but for example, the primary side, which is the high-voltage circuit 15H 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 the primary and secondary sides may be Y-Δ connection, YY connection, Δ-Y connection, or Δ-Δ connection. The load transformer 33 may also be an oil-immersed transformer or a dry-type transformer, and may be equipped with a contact prevention plate or be class B grounded. As shown in FIG. 2, the load breaker 34 is a device capable of interrupting an electrical circuit between the load transformer 33 and the load 32 (lighting load 32b) described above, or an electrical circuit between the power generation system transformer 13 and the load 32 (power load 32a) described above, and may be a molded case circuit breaker or a ground fault circuit interrupter. Furthermore, the secondary side of the above-mentioned system transformer 13 is connected not only to the power generation unit 11 and the conversion unit 12, but also to the power load 32a, as mentioned above, so it can be said to serve as both a power generation transformer and a load transformer.

[0080] <Control device> The control device may be a device that is connected to the above-mentioned earth fault overvoltage relay unit 16, reverse power relay unit 22, etc., and inputs a stop signal output from the earth fault overvoltage relay unit 16 or reverse power relay unit 22 to perform control such as stopping the conversion of the above-mentioned conversion unit 12, and may also be a smart logger, sequencer, computer, etc. In one power system 10, the number of control devices may be one or more. The power supply for the control device may be connected to an uninterruptible power supply (not shown) or the like, and input from the uninterruptible power supply, etc. Furthermore, the user may directly monitor, change settings, operate, etc. the control device, but this may also be done remotely via the Internet, telephone lines, etc.

[0081] <Other> The present invention is not limited to the above-described embodiment. The individual components or the overall structure, shape, dimensions, etc. of the zero-phase-sequence voltage detector 1 and the power system 10 can be modified as appropriate within the spirit of the present invention. The zero-phase voltage detector 1 may not have the zero-phase housing 6, the test capacitor 1a, or the test terminal. The zero-phase cable 3 may be wound (forward winding, reverse winding, figure-eight winding, coiled, etc.), and even when wound, it can be said that a safe distance between the voltage detector capacitor 2 and the voltage dividing capacitor 4 can be ensured by the length of the zero-phase cable 3. Referring to the zero-phase cable 3 in Figure 1, it appears that the zero-phase cable 3 begins where the three electrical circuits on the other end 2B of the three voltage detection capacitors 2 are combined into one and extends to the N terminal of the zero-phase housing 6, but the electrical circuits connecting the other end 2B of adjacent voltage detection capacitors 2 may also be composed of the zero-phase cable 3, and in this case, the length of the zero-phase cable 3 may include the part of the zero-phase cable 3 connecting the other end 2B of adjacent voltage detection capacitors 2. In addition, in FIG. 1, the three electric circuits on the other end 2B side of the three electroscopic capacitors 2 are gathered in the center, but they may be gathered on the other end 2B side of either the left or right electroscopic capacitor 2. The voltage dividing capacitor 4 does not have to include an internal voltage dividing capacitor 4a and an external voltage dividing capacitor 4b (in other words, it is not necessary to separate the internal voltage dividing capacitor 4a and the external voltage dividing capacitor 4b, but may include only the internal voltage dividing capacitor 4a or only the external voltage dividing capacitor 4b). Furthermore, the capacitance of the voltage dividing capacitor 4 may be a value that corresponds to the zero-phase cable 3 and to the value of a pre-made capacitor. In this case, if the divided voltage V2 is within a certain range of values ​​(for example, 18.22 V, 18.99 V, 19.50 V, etc.) or the voltage value of the zero-phase output current Z is within a certain range of values ​​(0.9112 V, 0.9496 V, 0.9750 V, etc.), the capacitance of the voltage dividing capacitor 4 may be a value that is slightly different from the capacitance of the voltage dividing capacitor 4 when the capacitance of the zero-phase cable 3 is negligibly small (in other words, the theoretical or ideal capacitance value). The zero-phase voltage detector possessed by the power system 10 is not limited to the zero-phase voltage detector 1 of the present invention, and the zero-phase voltage detector possessed by the power system 10 may, for example, be a zero-phase cable 3 that is not a shielded cable (the zero-phase cable 3 has a conductive core wire 3a that is not covered with a conductive shield layer 3c with an insulator 3b sandwiched between them), the zero-phase cable 3 may not be used as a capacitor, or the capacitance of the voltage dividing capacitor 4 may not be set to a value corresponding to the zero-phase cable 3.

[0082] The power system 10 does not need to have an instrument transformer 20, a sensor current transformer 21, or a reverse power relay unit 22 within the system connection unit 14, and furthermore, even when the earth fault overvoltage relay unit 16 detects an earth fault overvoltage state or when the reverse power relay unit 22 detects a reverse power generation state, a signal to stop the conversion of the conversion unit 12 is not output to the conversion unit 12, and the earth fault overvoltage relay unit 16, the reverse power relay unit 22, and the calculation unit 23 do not need to be located within a single device housing 24. Furthermore, the power system 10 does not necessarily have to include the calculation unit 23 or the device housing 24. The power system 10 may have a power storage unit that stores electricity, which may be the above-mentioned capacitor device 17, an uninterruptible power supply, or other storage batteries (batteries) such as lead-acid batteries, lithium-ion batteries, nickel-metal hydride batteries, or nickel-cadmium batteries. Alternatively, the power storage unit may store hydrogen generated by electrolysis of water using the power generated by the power generation unit 111 and extract electricity when needed using a fuel cell or other device. Alternatively, the power storage unit may store electricity as kinetic energy using a flywheel or as potential energy using pumped water. In this case, the power storage unit may be connected to the above-mentioned conversion unit 12 or an electric circuit such as the low-voltage circuit 15L, and may be used to store electricity output from the power generation unit 11 or the like, or to supply the charged electricity to the load 32 for consumption by the load 32 (self-consumption), or, if selling the electricity, to the grid K. In the power system 10, the above-mentioned system connection unit 14, zero-phase voltage detector 1, earth fault overvoltage relay unit 16, capacitor device 17, instrument transformer 20, sensor current transformer 21, reverse power relay unit 22, calculation unit 23, device housing 24, power generation circuit breaker 31, etc. may be provided within a single panel housing (in other words, a single distribution panel). In addition, the zero-phase voltage detector 1, earth fault overvoltage relay unit 16, capacitor device 17, instrument transformer 20, sensor current transformer 21, reverse power relay unit 22, calculation unit 23, device housing 24, power generation circuit breaker 31, etc. may be provided in a panel housing (such as a power generation connection panel, an added panel) separate from the panel housing (such as a system panel, an existing panel) in which the system connection unit 14 is provided. In the case where a load 32, a load transformer 33 (a system transformer 13 that serves as both a load transformer and a power generation transformer), a load breaker 34, and a grid connection unit 14 already exist in the power system 10, it can be said that in order to turn these existing loads 32, etc. into a self-consumption power generation plant, it is possible to retrofit the power generation unit 11, conversion unit 12, zero-phase voltage detector 1, earth fault overvoltage relay unit 16, capacitor device 17, sensor current transformer 21, reverse power relay unit 22, calculation unit 23, device housing 24, power generation breaker 31, etc. to the existing loads 32, etc. The system K relating to the power system 10 described above will be explained in detail below.

[0083] <System K> As shown in Fig. 2, grid K transmits (receives) power to the power system 10, and refers to the entire system through which electric power companies and the like supply electricity to consumers, and can also be called power grid K. Specifically, grid K includes facilities such as substations, transmission lines, and distribution lines, and may also include power plants. Grid K may also include the above-mentioned utility transformer 41a, 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 such 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 three-phase, three-wire (3φ3W) transmission lines. In order to reduce transmission losses during this process, the main long-distance transmission sections transmit electricity at as high a voltage as possible (for example, 6600V or 22000V). The electricity transmitted by system K is transformed (stepped down) in several stages near the point of consumption, and after the pole-mounted transformer, it is distributed via single-phase two-wire (1φ2W) or similar. System K may be a system (commercial power system) of an electric power company or the like, or may be a system independently owned by an organization such as a company or a local government, or a system within a plant (independent power system). [Industrial Applicability]

[0084] The zero-phase voltage detector of the present invention can be used in self-consumption solar power plants and the like, regardless of their power generation capacity or scale, and can be used not only in self-consumption solar power plants, but also in non-self-consumption solar power plants and plants that generate electricity using generators (such as AC motors) rotated by wind, water, wave, geothermal, etc., as well as in plants that do not have a power generation unit, and can be used both indoors and outdoors. The power system of the present invention can be used for self-consumption solar power plants and the like, regardless of their power generation capacity or scale, and can be used not only for self-consumption solar power plants, but also for 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. [Explanation of symbols]

[0085] 1 Zero-phase voltage detector 2. Electroscopic capacitor 2A voltage detection end 2B Voltage detector other end 3 Zero-phase cable 3A cable one end 3B Cable other end 3a conductive core wire 3b Insulator 3c Conductive shield layer 4 Voltage divider capacitor 4A voltage divider one end 4B Other end of voltage divider 4a internal voltage dividing capacitor 4b External voltage divider capacitor 5 Zero-phase transformer 6 Zero-phase enclosure 10 Power Systems 11 Power Generation Department 12 Conversion unit 13 System transformer 14 Grid connection 15H high voltage circuit 15Z Zero-phase output circuit 15C capacitor output circuit 16 Earth fault overvoltage relay 17 Capacitor device L Low voltage AC H High voltage AC current Z Zero-phase output current K lineage

Claims

1. A zero-phase voltage detector provided in an electric circuit, The electric circuit is a three-phase, three-wire circuit, The zero-phase voltage detector includes a voltage detection capacitor (2) having one voltage detection end (2A) connected to each of the three wires of the electric circuit, a zero-phase cable (3) having other voltage detection ends (2B) of the voltage detection capacitors (2) connected together to one cable end (3A), a voltage dividing capacitor (4) having one voltage dividing end (4A) connected to the other cable end (3B) of the zero-phase cable (3) and having the other voltage dividing end (4B) grounded, and a zero-phase voltage transformer (5) that transforms and outputs the voltage between the one voltage dividing end (4A) and the other voltage dividing end (4B) of the voltage dividing capacitor (4), The zero-phase cable (3) is a shielded cable in which a conductive core wire (3a) is covered with a conductive shield layer (3c) with an insulator (3b) sandwiched therebetween, The zero-phase cable (3) is used as a capacitor that stores electric charge between the conductive core wire (3a) and the conductive shield layer (3c), A zero-phase voltage detector characterized in that the capacitance of the voltage dividing capacitor (4) is set to a value corresponding to the zero-phase cable (3).

2. The zero-phase voltage detector has a zero-phase housing (6) that houses the zero-phase transformer (5), 2. The zero-phase voltage detector according to claim 1, wherein the voltage dividing capacitor (4) comprises an internal voltage dividing capacitor (4a) built into the zero-phase housing (6) and an external voltage dividing capacitor (4b) connected in parallel with the internal voltage dividing capacitor (4a) and provided outside the zero-phase housing (6).

3. A power system comprising a zero-phase voltage detector (1) according to claim 1 or 2, The power system includes a power generation unit (11), a conversion unit (12) that converts a direct current or alternating current from the power generation unit (11) into a low-voltage alternating current (L), a system transformer (13) that can transform the low-voltage alternating current (L) from the conversion unit (12) into a higher-voltage alternating current (H), and a system connection unit (14) that connects the system transformer (13) to a system (K), The system connection unit (14) a high-voltage line (15H) connected between the system transformer (13) and a system (K) for passing a high-voltage AC current (H) and provided with the zero-phase voltage detector (1); an earth fault overvoltage relay unit (16) connected to a zero-phase output circuit (15Z) through which a zero-phase output current (Z) output from the zero-phase transformer (5) in the zero-phase voltage detector (1) flows, and detecting an earth fault overvoltage state based on the zero-phase output current (Z); a capacitor device (17) connected to a capacitor output circuit (15C) that supplies power from a power source to the earth fault overvoltage relay unit (16) and that supplies power from a power source to the earth fault overvoltage relay unit (16) during a power outage.

4. 1. A power system having a zero-sequence voltage detector, comprising: The power system includes a power generation unit (11), a conversion unit (12) that converts a direct current or alternating current from the power generation unit (11) into a low-voltage alternating current (L), a system transformer (13) that can transform the low-voltage alternating current (L) from the conversion unit (12) into a higher-voltage alternating current (H), and a system connection unit (14) that connects the system transformer (13) to a system (K), The system connection unit (14) a high-voltage circuit (15H) connected between the system transformer (13) and a system (K) for passing a high-voltage AC current (H) and provided with the zero-phase voltage detector; a ground fault overvoltage relay unit (16) connected to a zero-phase output circuit (15Z) through which a zero-phase output current (Z) output from the zero-phase transformer (5) in the zero-phase voltage detector flows, and detecting a ground fault overvoltage state based on the zero-phase output current (Z); a capacitor device (17) connected to a capacitor output circuit (15C) that supplies power from a power source to the earth fault overvoltage relay unit (16) and that supplies power from a power source to the earth fault overvoltage relay unit (16) during a power outage.

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