Detection device, power supply system, and detection method

Abstract

To realize a failure detection method more excellent than ever, for a power supply system equipped with a distributed power source.SOLUTION: A detection device (100) detects occurrence of a failure in a power supply system (1) equipped with a distributed power source (210) that supplies three-phase AC power to a power reception facility (RF) through a distribution line (110), and also can connect to a power system (SYS). In a state where the distributed power source (210) is disconnected from the power system (SYS), the detection device (100) supplies a test signal (TS) which has a test frequency different from a commercial frequency to the distribution line (110), determines whether or not a short circuit has occurred in the power supply system (1) on the basis of at least one of a test frequency component of a voltage (V) in a prescribed phase and a test frequency component of a current (I) in the prescribed phase generated with the supply of the test signal (TS), and determines whether or not a ground fault has occurred in the power supply system (1) on the basis of at least one of a test frequency component of a zero-phase voltage (V0) and a test frequency component of a zero-phase current (I0) generated with the supply of the test signal (TS).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One aspect of the present invention relates to a detection device for detecting the occurrence of a fault in a power supply system equipped with distributed power sources. [Background technology]

[0002] Various technologies have been proposed for protecting power supply systems (e.g., microgrids) that include distributed power sources that can be connected to a power grid. For example, Patent Document 1 listed below proposes a method for detecting the occurrence of a short circuit in a power supply system that is disconnected from the power grid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-110710 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present invention is to provide a fault detection method for a power supply system equipped with distributed power sources that is superior to conventional methods. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, a detection device according to one embodiment of the present invention is a detection device that supplies three-phase AC power to power receiving equipment through a distribution line and detects the occurrence of a fault in a power supply system that includes a distributed power source connectable to a power grid, wherein when the distributed power source is disconnected from the power grid, the detection device supplies an inspection signal to the distribution line having an inspection frequency that is different from the commercial frequency of the power grid, and determines whether or not a short circuit has occurred in the power supply system based on at least one of an inspection frequency component of a voltage of a specified phase in the distribution line and an inspection frequency component of a current of the specified phase in the distribution line that are generated when the inspection signal is supplied to the distribution line, and determines whether or not a ground fault has occurred in the power supply system based on at least one of an inspection frequency component of a zero-phase voltage in the distribution line and an inspection frequency component of a zero-phase current in the distribution line that are generated when the inspection signal is supplied to the distribution line.

[0006] Furthermore, a detection method according to one aspect of the present invention is a detection method for detecting the occurrence of a fault in a power supply system that supplies three-phase AC power to power receiving equipment through a distribution line and includes a distributed power source connectable to a power grid, the detection method including the steps of: supplying an inspection signal having an inspection frequency different from the commercial frequency of the power grid to the distribution line while the distributed power source is disconnected from the power grid; determining whether or not a short circuit has occurred in the power supply system based on at least one of an inspection frequency component of a voltage of a predetermined phase in the distribution line and an inspection frequency component of a current of the predetermined phase in the distribution line that are generated as the inspection signal is supplied to the distribution line; and determining whether or not a ground fault has occurred in the power supply system based on at least one of an inspection frequency component of a zero-phase voltage in the distribution line and an inspection frequency component of a zero-phase current in the distribution line that are generated as the inspection signal is supplied to the distribution line. [Effects of the Invention]

[0007] According to one aspect of the present invention, a fault detection method that is superior to conventional methods can be realized for a power supply system equipped with distributed power sources. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows an example of the configuration of a power supply system and its peripherals according to a first embodiment. [Figure 2] 2 shows an example of the configuration of a detection device in the power supply system of the first embodiment. [Figure 3] 4 is a logic table showing an example of each determination process in the control unit of the detection device of the first embodiment. [Figure 4] 4 is a flowchart illustrating a processing flow in the detection device of the first embodiment. [Figure 5] 1 shows a simplified equivalent circuit for explaining the mechanism of ground fault detection in the first embodiment. [Figure 6] FIG. 10 is a diagram illustrating a modified example of the first embodiment. [Figure 7] 1 shows an example of the configuration of a power supply system and its peripherals according to a second embodiment. [Figure 8] 10 shows an example of the configuration of a detection device in the power supply system of the second embodiment. [Figure 9] 10 is a flowchart illustrating a processing flow in the detection device of the second embodiment. [Figure 10] 10 is a flowchart illustrating the flow of an inspection process for a branch distribution line in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiment 1] The first embodiment will be described below. For convenience of explanation, components having the same functions as those described in the first embodiment will be denoted by the same reference numerals in the following embodiments, and the description thereof will not be repeated. For the sake of brevity, the description of well-known technical matters will also be omitted as appropriate.

[0010] Unless otherwise stated, the components and numerical values ​​described in this specification are merely examples. Therefore, unless otherwise stated, the positional relationships and connection relationships of the components are not limited to the examples in the drawings. Unless otherwise stated, the term "connected" in this specification means "electrically connected."

[0011] (Outline of Power Supply System 1) FIG. 1 shows an example of the configuration of a power supply system 1 and its peripherals according to a first embodiment. In FIG. 1, a three-phase AC electrical system is shown as a single-line diagram. In this specification, the three phases of the three-phase AC are referred to as the first phase, the second phase, and the third phase. As an example, the first phase is the U phase, the second phase is the V phase, and the third phase is the W phase. The power supply system 1 includes a detection device 100 and a distributed power source 210. The power supply system 1 is, for example, a microgrid.

[0012] The power receiving facility RF is an example of a load that receives power from the power supply system 1. The distributed power sources 210 in the power supply system 1 are configured to be able to supply power to the power receiving facility RF through the power distribution line 110. The power receiving facility RF is located downstream of the distributed power sources 210. In the example of FIG. 1, for clarity of explanation, only one power receiving facility RF is shown.

[0013] The power supply system 1 can be connected to a power system SYS. In the example of Fig. 1, the power system SYS is equivalently shown as an AC power source. In the example of Fig. 1, a distributed power source 210 can be connected to the power system SYS. The power system SYS is located upstream of the distributed power source 210.

[0014] In the example of Fig. 1, the distributed power generation 210 is connected to the power system SYS via a circuit breaker CB. During normal operation of the power system, the circuit breaker CB is maintained in the on state. Therefore, when the power system SYS is healthy, the distributed power generation 210 can supply power to the power receiving facility RF in cooperation with the power system SYS.

[0015] On the other hand, for example, if some abnormality occurs in the power system SYS, the circuit breaker CB is opened (turned off). The circuit breaker CB is opened, for example, in accordance with a command from a control device (not shown) owned by the manager of the power system SYS. When the circuit breaker CB is opened, the distributed power source 210 is configured to operate autonomously (single-operated) and supply power to the power receiving facility RF.

[0016] 1 includes an emergency power generator 204, a power storage device 206, and a solar power generation device 208. As an example, the power storage device 206 includes a battery and an inverter. The solar power generation device 208 includes a solar panel and an inverter. The battery of the power storage device 206 can store power supplied from a device external to the power storage device 206 (e.g., the emergency power generator 204).

[0017] If the distributed power sources 210 are made to start independent operation when a fault (e.g., a short circuit or a ground fault) occurs in the power supply system 1, there is a risk that an excessive current will flow in the distributed power sources 210. Such an excessive current may shorten the life of the distributed power sources 210.

[0018] Therefore, the power supply system 1 includes a detection device 100 that detects the occurrence of a fault in the power supply system 1. Specifically, the detection device 100 detects the occurrence of a short circuit and a ground fault in the power supply system 1. Therefore, the detection device 100 can protect the distributed power source 210. For this reason, the detection device according to one embodiment of the present disclosure may be referred to as a protection device.

[0019] 1 indicates that a short circuit or a ground fault has occurred in the power distribution line 110. It should be noted that the expression "a short circuit or a ground fault in the power distribution line 110" in this specification does not only mean "a short circuit or a ground fault in the power distribution line 110 itself," but also generally means "a short circuit or a ground fault in the path of power transmission by the power distribution line 110."

[0020] 1 may also represent, for example, a short circuit or a ground fault in the power receiving facility RF. For this reason, the expression "short circuit or ground fault in the power supply system 1" in this specification represents a broad concept that includes "short circuit or ground fault in the power receiving facility RF."

[0021] The detection device 100 detects the occurrence of a short circuit and a ground fault in the power supply system 1 based on the measured values ​​of each electrical quantity generated in the power supply system 1. In the example of Fig. 1, the power supply system 1 has a voltage sensor 191, a current sensor 192, a zero-phase voltage sensor 193, and a zero-phase current sensor 194. In the example of Fig. 1, these sensors may be located on the power distribution line 110 between the distributed power source 210 and the power receiving facility RF.

[0022] The voltage sensor 191 collectively refers to (i) a first-phase voltage sensor that detects a first-phase voltage (e.g., a U-phase voltage), (ii) a second-phase voltage sensor that detects a second-phase voltage (e.g., a V-phase voltage), and (iii) a third-phase voltage sensor that detects a third-phase voltage (e.g., a W-phase voltage) in the power distribution line 110. The voltage sensor 191 may be, for example, a voltage transformer (VT).

[0023] Therefore, the voltage sensor 191 can detect the voltage V of a predetermined phase in the power distribution line 110. The predetermined phase may be any one of the first to third phases. In the first embodiment, as an example, the case where the predetermined phase is the first phase will be described. Therefore, the voltage V in the following description represents the U-phase voltage in the power distribution line 110 unless otherwise specified.

[0024] The current sensor 192 collectively refers to (i) a first-phase current sensor that detects a first-phase current (e.g., a U-phase current), (ii) a second-phase current sensor that detects a second-phase current (e.g., a V-phase current), and (iii) a third-phase current sensor that detects a third-phase current (e.g., a W-phase current) in the power distribution line 110. The current sensor 192 may be, for example, a current transformer (CT).

[0025] Therefore, the current sensor 192 can detect the current I of the above-mentioned predetermined phase in the power distribution line 110. In the following description, the voltage I represents the U-phase current in the power distribution line 110 unless otherwise specified.

[0026] The zero-phase-sequence voltage sensor 193 detects a zero-phase-sequence voltage V0 in the power distribution line 110. The zero-phase-sequence voltage sensor 193 may be, for example, a ZPD (Zero-Phase-sequence Potential Device). A ZPD is also called a ZVT (Zero-Phase Voltage Transformer). The zero-phase-sequence current sensor 194 detects a zero-phase-sequence current I0 in the power distribution line 110. The zero-phase-sequence current sensor 194 may be, for example, a ZCT (Zero-Phase Current Transformer).

[0027] (Configuration example of detection device 100) 2 shows an example of the configuration of the detection device 100. The detection device 100 includes a control unit 102, a test signal generation unit 104, a first acquisition unit 106, a second acquisition unit 107, and a test frequency component derivation unit .

[0028] The control unit 102 comprehensively controls each component in the power supply system 1. In the example of the first embodiment, it is assumed that a trigger signal TG is supplied from the circuit breaker CB to the detection device 100 when the circuit breaker CB is opened. Upon receiving the trigger signal TG, the control unit 102 starts the operation of the inspection signal generation unit 104 and the inspection frequency component derivation unit 108. Therefore, in the following description, unless otherwise specified, it is assumed that the distributed power sources 210 are disconnected from the power system SYS.

[0029] The test signal generating unit 104 generates a test signal TS having a certain frequency and supplies the TS to the power distribution line 110. In this specification, the frequency of the TS is referred to as the "test frequency." The test frequency may be different from the commercial frequency of the power system SYS (e.g., the fundamental frequency of the voltage output by the power system SYS). This makes it possible to prevent the TS from interfering with electrical signals at the commercial frequency.

[0030] The test frequency may be higher or lower than the commercial frequency. In the first embodiment, a case where the test frequency is higher than the commercial frequency is exemplified. For this reason, the TS in the first embodiment may be referred to as a harmonic signal. Furthermore, the test signal generating unit 104 in the first embodiment may be referred to as a harmonic signal generating unit. As an example, when the commercial frequency is 50 Hz, the test frequency may be 125 Hz (2.5 times the commercial frequency).

[0031] The TS may be a constant voltage signal (an AC voltage having a constant amplitude) or a constant current signal (an AC current having a constant amplitude). In the first embodiment, the case where the TS is a constant current signal is exemplified. Therefore, the test signal generating unit 104 in the first embodiment can be regarded as an AC current source in an equivalent circuit described later.

[0032] The first acquisition unit 106 has a voltage value acquisition unit 1061 and a current value acquisition unit 1062. As TS is supplied to the power distribution line 110, V corresponding to the TS is generated in the power distribution line 110. Therefore, the voltage value acquisition unit 1061 acquires the detected value of V from the voltage sensor 191 at predetermined time intervals and generates time-series data of the detected value. The voltage value acquisition unit 1061 supplies the time-series data to the inspection frequency component derivation unit 108.

[0033] Furthermore, as TS is supplied to the power distribution line 110, I corresponding to the TS is generated in the power distribution line 110. Therefore, the current value acquiring unit 1062 acquires the detected value of I from the current sensor 192 at the above-mentioned time intervals and generates time-series data of the detected value. The current value acquiring unit 1062 supplies the time-series data to the inspection frequency component derivation unit 108.

[0034] The second acquiring unit 107 has a zero-phase-sequence voltage value acquiring unit 1071 and a zero-phase-sequence current value acquiring unit 1072. As TS is supplied to the power distribution line 110, V0 corresponding to the TS is generated in the power distribution line 110. Therefore, the zero-phase-sequence voltage value acquiring unit 1071 acquires the detection value of V0 from the zero-phase-sequence voltage sensor 193 at the above-mentioned time intervals and generates time-series data of the detection value. The zero-phase-sequence voltage value acquiring unit 1071 supplies the time-series data to the inspection frequency component deriving unit 108.

[0035] Furthermore, as TS is supplied to the power distribution line 110, I0 corresponding to the TS is generated in the power distribution line 110. Therefore, the zero-phase-sequence current value acquiring unit 1072 acquires the detection value of I0 from the zero-phase-sequence current sensor 194 at the above-mentioned time intervals and generates time-series data of the detection value. The zero-phase-sequence current value acquiring unit 1072 supplies the time-series data to the inspection frequency component deriving unit 108.

[0036] The inspection frequency component derivation unit 108 has a first derivation unit 1081 and a second derivation unit 1082. The first derivation unit 1081 derives a voltage signal Vs indicating the inspection frequency component of V based on the time-series data of the detection value of V supplied from the voltage value acquisition unit 1061. Vs may also be referred to as the inspection frequency component of the voltage of a predetermined phase.

[0037] Furthermore, the first derivation unit 1081 derives a current signal Is indicating the inspection frequency component of I based on the time-series data of the detection value of I supplied from the current value acquisition unit 1062. Is may also be referred to as the inspection frequency component of a current of a predetermined phase. As an example, the first derivation unit 1081 may derive Vs from V and Is from I using any digital filter.

[0038] The second derivation unit 1082 derives a voltage signal V0s indicating the test frequency component of V0 based on the time series data of the detection value of V0 supplied from the zero-phase sequence voltage value acquisition unit 1071. V0s may also be referred to as the test frequency component of the zero-phase sequence voltage.

[0039] The second derivation unit 1082 derives a current signal I0s indicating the test frequency component of I0 based on the time-series data of the detected value of I0 supplied from the zero-phase current value acquisition unit 1072. I0s may also be referred to as the test frequency component of the zero-phase current. The second derivation unit 1082 may derive V0s from V0 and I0s from I0 using any digital filter.

[0040] The control unit 102 has a short circuit determination unit 1021, a ground fault determination unit 1022, and an independent operation determination unit 1023. First, an example of the processing of the short circuit determination unit 1021 will be described.

[0041] (Example of processing by short circuit determination unit 1021) The short-circuit determining unit 1021 acquires Vs and Is from the first derivation unit 1081. Then, the short-circuit determining unit 1021 determines whether or not a short circuit has occurred in the power supply system 1 based on at least one of Vs and Is.

[0042] In the example of the first embodiment, Is corresponds to TS. Since TS in the first embodiment is a constant current signal, the peak value of Is is considered to be roughly constant regardless of time transition. Therefore, the first derivation unit 1081 may determine whether or not a short circuit has occurred in the power supply system 1 based on Vs.

[0043] (Example of judgment process based on Vs) The short circuit determination unit 1021 may compare Vs_peak, which is the peak value of Vs, with a predetermined threshold Vth to determine whether a short circuit has occurred in the power supply system 1. Vth may also be referred to as a voltage threshold for short circuit determination.

[0044] Based on the comparison result between Vs_peak and Vth, the short circuit determination unit 1021 outputs a first determination signal SG1 indicating the determination result as to whether or not a short circuit has occurred in the power supply system 1. SG1 may also be referred to as a short circuit determination signal.

[0045] For example, when Vs_peak is smaller than Vth, that is, when Vs_peak < Vth, the short - circuit determination unit 1021 determines that a short - circuit has occurred in the power supply system 1. In the example of Embodiment 1, the logical value "1" of SG1 represents that a short - circuit has occurred in the power supply system 1. Therefore, in this example, when Vs_peak < Vth, the short - circuit determination unit 1021 outputs SG1 = 1.

[0046] On the other hand, when Vs_peak is greater than or equal to Vth, that is, when Vs_peak ≥ Vth, the short - circuit determination unit 1021 determines that no short - circuit has occurred in the power supply system 1. In the example of Embodiment 1, the logical value "0" of SG1 represents that no short - circuit has occurred in the power supply system 1. Therefore, in this example, when Vs_peak ≥ Vth, the short - circuit determination unit 1021 outputs SG1 = 0.

[0047] (Example of determination process based on Zs) The short - circuit determination unit 1021 may derive the short - circuit impedance Zs at the inspection frequency as Zs = Vs_peak / Is_peak …(1) where Is_peak in Equation (1) is the peak value of Is.

[0048] The short - circuit determination unit 1021 may determine whether a short - circuit has occurred in the power supply system 1 by comparing Zs with a predetermined threshold value Zth. Zth may be referred to as an impedance threshold in short - circuit determination.

[0049] For example, when Zs is smaller than Zth, that is, when Zs < Zth, the short - circuit determination unit 1021 determines that a short - circuit has occurred in the power supply system 1. Therefore, in this example, when Zs < Zth, the short - circuit determination unit 1021 outputs SG1 = 1.

[0050] On the other hand, when Zs is greater than or equal to Zth, that is, when Zs ≥ Zth, the short-circuit determination unit 1021 determines that no short circuit has occurred in the power supply system 1. Therefore, in this example, when Zs ≥ Zth, the short-circuit determination unit 1021 outputs SG1 = 0.

[0051] In an ideal example in Embodiment 1, Is_peak is constant regardless of the passage of time. Therefore, the determination process based on Zs in the ideal example is equivalent to the determination process based on Vs described above.

[0052] (Examples of determination processes based on Vs and Zs) However, in reality, Is_peak can change over time. Therefore, by performing determination based on both Vs and Zs, it is possible to more accurately determine whether a short circuit has occurred in the power supply system 1.

[0053] FIG. 3 is a logic table showing an example of each determination process in the control unit 102. In FIG. 3, the logical value "1" represents "True", and the logical value "0" represents "False". As an example, the short-circuit determination unit 1021 may output SG1 based on both Vs and Zs as shown in the first table TB1 of FIG. 3.

[0054] In the example of FIG. 3, the short-circuit determination unit 1021 a logical value ST1 indicating whether "Vs_peak < Vth" is satisfied, and a logical value ST2 indicating whether "Zs < Zth" is satisfied, and outputs them respectively.

[0055] Then, the short-circuit determination unit 1021 outputs the logical sum of ST1 and ST2 as SG1. That is, the short-circuit determination unit 1021 outputs SG1 defined as SG1 = ST1 + ST2...(2) as the determined SG1.

[0056] In the example of FIG. 3, the short-circuit determination unit 1021 outputs SG1 = 0 only when ST1 = 0 and ST2 = 0. That is, SG1 = 0 is output from the short-circuit determination unit 1021 only when (i) Vs_peak ≧ Vth and (ii) Zs ≧ Zth. In other cases, SG1 = 1 is output from the short-circuit determination unit 1021.

[0057] (Example of the process of the ground fault determination unit 1022) The ground fault determination unit 1022 acquires V0s and I0s from the second derivation unit 1082. Then, the ground fault determination unit 1022 determines whether or not a ground fault has occurred in the power supply system 1 based on at least one of V0s and I0s.

[0058] (Example of the determination process based on V0s) The ground fault determination unit 1022 may determine whether or not a ground fault has occurred in the power supply system 1 by comparing V0s_peak, which is the peak value of V0s, with a predetermined threshold value V0th. V0th may be referred to as a voltage threshold value in ground fault determination.

[0059] Then, the ground fault determination unit 1022 outputs a second determination signal SG2 indicating the determination result as to whether or not a ground fault has occurred in the power supply system 1 based on the comparison result between V0s_peak and V0th. SG2 may be referred to as a ground fault determination signal.

[0060] For example, when V0s_peak is smaller than V0th, that is, when V0s_peak < V0th, the ground fault determination unit 1022 determines that a ground fault has occurred in the power supply system 1. In the example of Embodiment 1, the logical value “1” of SG2 represents that a ground fault has occurred in the power supply system 1. Therefore, in this example, when V0s_peak < V0th, the ground fault determination unit 1022 outputs SG2 = 1.

[0061] On the other hand, when V0s_peak is greater than or equal to V0th, that is, when V0s_peak ≧ V0th, the ground fault determination unit 1022 determines that no ground fault has occurred in the power supply system 1. In the example of Embodiment 1, the logical value "0" of SG2 indicates that no ground fault has occurred in the power supply system 1. Therefore, in this example, when V0s_peak ≧ V0th, the ground fault determination unit 1022 outputs SG2 = 0.

[0062] (Example of determination process based on Z0s) The ground fault determination unit 1022 may derive the ground fault impedance Z0s at the inspection frequency as Z0s = V0s_peak / I0s_peak …(3) as shown. I0s_peak in Equation (3) is the peak value of I0s.

[0063] The ground fault determination unit 1022 may determine whether a ground fault has occurred in the power supply system 1 by comparing Z0s with a predetermined threshold value Z0th. Z0th may be referred to as an impedance threshold in ground fault determination.

[0064] For example, when Z0s is less than Z0th, that is, when Z0s < Z0th, the ground fault determination unit 1022 determines that a ground fault has occurred in the power supply system 1. Therefore, in this example, when Z0s < Zth, the ground fault determination unit 1022 outputs SG2 = 1.

[0065] On the other hand, when Z0s is greater than or equal to Z0th, that is, when Z0s ≧ Z0th, the ground fault determination unit 1022 determines that no ground fault has occurred in the power supply system 1. Therefore, in this example, when Z0s ≧ Z0th, the ground fault determination unit 1022 outputs SG1 = 0.

[0066] (Example of determination process based on I0s) I0 is a current caused by the imbalance of the three-phase alternating current in the power supply system 1. Therefore, even when TS is a constant current signal, I0s_peak can change over time.

[0067] Therefore, the ground fault determination unit 1022 may determine whether a ground fault has occurred in the power supply system 1 by comparing I0s_peak with a predetermined threshold value I0th. I0th may be referred to as a current threshold value in ground fault determination.

[0068] For example, when I0s_peak is greater than or equal to I0th, that is, when I0s_peak≧I0th, the ground fault determination unit 1022 determines that a ground fault has occurred in the power supply system 1. Therefore, in this example, when I0s_peak≧I0th, the ground fault determination unit 1022 outputs SG2 = 1.

[0069] On the other hand, when I0s_peak is smaller than I0th, that is, when I0s_peak < I0th, the ground fault determination unit 1022 determines that no ground fault has occurred in the power supply system 1. Therefore, in this example, when I0s_peak < I0th, the ground fault determination unit 1022 outputs SG2 = 0.

[0070] (Example of determination process based on Vs, Zs, and I0s) The ground fault determination unit 1022 may determine whether a short circuit has occurred in the power supply system 1 based on two or more of Vs, Zs, and I0s. Therefore, as an example, the ground fault determination unit 1022 may determine whether a short circuit has occurred in the power supply system 1 based on Vs, Zs, and I0s.

[0071] In this case, for example, the ground fault determination unit 1022 may output SG2 based on Vs, Zs, and I0s as shown in the second table TB of FIG. 3.

[0072] In the example of FIG. 3, the ground fault determination unit 1022 A logical value GT1 indicating whether "V0s_peak < Vth" is satisfied, A logical value GT2 indicating whether "Z0s < Z0th" is satisfied, A logical value GT3 indicating whether "I0s ≧ I0th" is satisfied, are each output.

[0073] And the ground fault determination unit 1022 outputs the logical sum of GT1, GT2, and GT3 as SG2. That is, the ground fault determination unit 1022 defines SG2 as SG2 = GT1 + GT2 + GT3 …(4) and outputs SG2.

[0074] In the example of FIG. 3, the ground fault determination unit 1022 outputs SG2 = 0 only when ST1 = 0, ST2 = 0, and ST = 3. That is, SG2 = 0 is output from the ground fault determination unit 1022 only when (i) V0s_peak ≧ V0th, (ii) Z0s ≧ Z0th, and (iii) I0s_peak < I0th. In other cases, SG2 = 1 is output from the ground fault determination unit 1022.

[0075] (Example of the process of the self - operation determination unit 1023) The self - operation determination unit 1023 (i) acquires SG1 from the short - circuit determination unit 1021 and (ii) acquires SG2 from the ground fault determination unit 1022. The self - operation determination unit 1023 determines whether to permit the self - operation of the distributed power source 210 based on SG1 and SG2. Then, the self - operation determination unit 1023 may output a third determination signal SG3 indicating the determination result of whether to permit the self - operation of the distributed power source 210. SG3 may be referred to as a self - operation determination signal.

[0076] In the example of the first embodiment, a logic value of "1" for SG3 indicates that the distributed generation 210 is permitted to operate independently. Therefore, in this specification, SG3=1 generally corresponds to an enable signal for the distributed generation 210. On the other hand, a logic value of "0" for SG3 indicates that the distributed generation 210 is not permitted to operate independently (is prohibited from operating independently). Therefore, in this specification, SG3=0 generally corresponds to a disable signal for the distributed generation 210.

[0077] The independent operation determination unit 1023 may output SG3 based on SG1 and SG2, as shown in the third table TB3 in FIG.

[0078] In the example of Fig. 3, the independent operation determination unit 1023 outputs the negative OR (NOR) of SG1 and SG2 as SG3. SG3=NOR(SG1,SG2) …(5) The output SG3 is defined as follows.

[0079] 3, SG3=1 is output from the isolated operation determination unit 1023 only when (i) SG1=0 and (ii) SG2=0. In other cases, SG3=0 is output from the isolated operation determination unit 1023.

[0080] In this way, the isolated operation determination unit 1023 in the example of embodiment 1 permits isolated operation of the distributed power source 210 only when neither a short circuit nor a ground fault is detected in the power supply system 1. On the other hand, the isolated operation determination unit 1023 prohibits isolated operation of the distributed power source 210 when a short circuit or a ground fault is detected in the power supply system 1 (more strictly, when at least one of a short circuit and a ground fault is detected).

[0081] The isolated operation determination unit 1023 supplies SG3 to the dispersed generation 210. In this specification, SG3=1 serves as a start signal for starting up the dispersed generation 210 that is currently stopped. The start signal is an example of an enable signal.

[0082] (Example of processing flow in detection device 100) Fig. 4 is a flowchart illustrating the flow of processing in the detection device 100. The processing in Fig. 4 is started when the control unit 102 acquires the above-mentioned TG from the circuit breaker CB. At the start of the processing in Fig. 4, it is assumed that the operation of the distributed generation 210 is stopped.

[0083] In step S1, the test signal generating unit 104 generates a test signal TS and supplies the TS to the power distribution line 110.

[0084] In step S2, the first acquisition unit 106 acquires V from the voltage sensor 191 and acquires I from the current sensor 192. Next, the first derivation unit 1081 derives Vs based on V and derives Is based on I.

[0085] In step S3, the second acquisition unit 107 acquires V0 from the zero-phase-sequence voltage sensor 193 and acquires I0 from the zero-phase-sequence current sensor 194. Next, the second derivation unit 1082 derives V0s based on V0 and derives I0s based on I0.

[0086] For clarity of illustration, Fig. 4 illustrates an example in which step S3 follows step S2. However, it should be noted that the order of steps S2 and S3 is not limited to the example in Fig. 4. For example, step S3 may precede step S2. Alternatively, the processing of step S2 and the processing of step S3 may be executed in parallel. This also applies to steps S23 and S24 described in embodiment 2.

[0087] In step S4, the control unit 102 determines whether a short circuit or a ground fault has occurred in the power supply system 1, based on the electrical quantities derived in steps S2 and S3. Specifically, as described above, the short circuit determination unit 1021 outputs SG1 based on at least one of Vs and Is. Then, the ground fault determination unit 1022 outputs SG2 based on at least one of V0s and I0s.

[0088] If the result of step S4 is YES, that is, if a short circuit or a ground fault is detected in the power supply system 1, proceed to step S5. According to the example of embodiment 1, if the result of step S4 is YES, the logical value of at least one of SG1 and SG2 is 1.

[0089] Therefore, in step S5, the independent operation determination unit 1023 outputs SG3=0. That is, the independent operation determination unit 1023 prohibits independent operation of the dispersed generation 210. Then, the process returns to step S1. In this way, in the example of Fig. 4, the processes of S1 to S5 are repeated until step S4 becomes NO.

[0090] On the other hand, if the result of step S4 is NO, that is, if neither a short circuit nor a ground fault is detected in the power supply system 1, the process proceeds to step S6. According to the example of embodiment 1, if the result of step S4 is NO, the logical values ​​of SG1 and SG2 are both 0.

[0091] Therefore, in step S6, the isolated operation determination unit 1023 outputs SG3 = 1. Therefore, the isolated operation determination unit 1023 supplies a start-up signal to the dispersed power source 210, thereby permitting the dispersed power source 210 to operate in an isolated manner. Then, the process proceeds to step S7.

[0092] In step S7, the inspection signal generating unit 104 stops supplying the TS to the power distribution line 110. This completes the series of processes performed by the control unit 102 to detect whether a short circuit or a ground fault has occurred in the power supply system 1.

[0093] (Ground fault detection mechanism in embodiment 1) Fig. 5 shows a simplified equivalent circuit for explaining the mechanism of ground fault detection in embodiment 1. In the example of Fig. 5, a current source 510 represents the inspection signal generating unit 104. Therefore, the current Is output from the current source 510 corresponds to the inspection signal TS. A capacitor 520 represents the capacitance to ground of the power distribution line 110.

[0094] When the power supply system 1 is healthy, that is, when no fault occurs in the power supply system 1, the impedance to ground of the power distribution line 110 is approximately equal to the impedance of the capacitor 520. Therefore, when the power supply system 1 is healthy, almost no current Is flows to the ground.

[0095] Even if a short circuit occurs in the power supply system 1, the impedance to ground of the power distribution line 110 is approximately equal to the impedance of the capacitor 520. Therefore, even if a short circuit occurs in the power supply system 1, almost no current Is flows to the ground.

[0096] On the other hand, when a ground fault occurs in the power supply system 1, a ground fault path is generated in the power supply system 1. Fig. 5 illustrates a ground fault path passing through the ground electrodes GND1 and GND2. Therefore, when a ground fault occurs, the impedance to ground of the power distribution line 110 decreases.

[0097] As a result, a current I0s, which is a part of the current Is, flows through the ground fault path as a zero-phase current. Therefore, the power supply system 1 is provided with a zero-phase current sensor 194 to detect I0, which is a zero-phase current corresponding to I0s.

[0098] Furthermore, a zero-phase voltage V0s corresponding to the current I0s is generated in the power supply system 1. Therefore, the power supply system 1 is provided with a zero-phase voltage sensor 193 to detect V0, which is a zero-phase voltage corresponding to V0s.

[0099] As described above, the second derivation unit 1082 of the control unit 102 can derive I0s based on I0 and V0s based on V0. Therefore, the power supply system 1 can effectively detect a ground fault.

[0100] (Effects of the First Embodiment) According to the first embodiment, unlike the conventional technology, not only can a short circuit be detected in a power supply system equipped with distributed power sources, but also a ground fault can be detected in the power supply system. Thus, according to the first embodiment, a fault detection method for the power supply system that is superior to conventional methods can be realized.

[0101] Additionally, in the first embodiment, SG3 is output in response to SG1 and SG2. This allows the distributed power sources to be started based on both the result of short-circuit detection and the detection of a ground fault. Therefore, the risk of the distributed power sources being started when a fault occurs in the power supply system can be reduced compared to the conventional case. In this way, according to the first embodiment, it is also possible to protect the distributed power sources in the power supply system more effectively than the conventional case.

[0102] Furthermore, according to the first embodiment, it is no longer necessary for workers to manually investigate the locations of short circuits and ground faults in the power supply system, which contributes to reducing the maintenance costs of the power supply system.

[0103] In addition, according to the first embodiment, occurrence of a short circuit or a ground fault in the power supply system can be detected more quickly than when an operator manually investigates the location of the short circuit or the ground fault in the power supply system. Therefore, the first embodiment also contributes to speeding up the recovery from an abnormality in the power supply system. Therefore, the first embodiment also provides benefits to consumers (e.g., users of power receiving facilities) who receive power from the power supply system.

[0104] As described above, the voltage sensor 191 can detect the voltages of the first to third phases in the power distribution line 110. The current sensor 192 can detect the currents of the first to third phases in the power distribution line 110. Therefore, in the first embodiment, the above-described short-circuit detection process may be executed for each of the first to third phases. This makes it possible to more reliably detect the occurrence of a short circuit in the power supply system.

[0105] [Modification] In the first embodiment, the test signal generating unit 104 generates the test signal TS. However, the test signal generating unit 104 may further generate a signal other than the TS. As an example, the test signal generating unit 104 may further generate a second signal TS2 having a second test frequency. In comparison with TS2, the TS may be referred to as a first test signal. The test frequency, which is the frequency of the TS, may be referred to as a first test frequency.

[0106] To prevent TS2 from interfering with the electrical signal of the commercial frequency, the second test frequency is set to a frequency different from the commercial frequency. The second test frequency may be higher or lower than the commercial frequency. In addition, to prevent TS2 from interfering with TS, it is preferable that the second test frequency is also set to a frequency different from the first test frequency. The second test frequency may be higher or lower than the first test frequency.

[0107] Fig. 6 is a diagram for explaining a modified example of the first embodiment. Fig. 6 is a diagram paired with Fig. 5. In the example of Fig. 6, the inspection signal generating unit 104 is represented by a current source 510 and a current source 620. In the example of Fig. 6, the current source 510 may be referred to as a first current source, and the current source 620 may be referred to as a second current source.

[0108] As described above, the current source 510 supplies TS to the power distribution line 110. Meanwhile, the current source 620 supplies TS2 to the ground. In the example of Figure 6, the current source 620 supplies TS2 to the ground electrode GND3.

[0109] 6 illustrates a ground fault path passing through the ground electrodes GND1 and GND3. Therefore, a zero-phase current I0s2 corresponding to TS2 flows through the ground fault path. By further supplying TS2 to the ground, the value of I0 detected by the zero-phase current sensor 194 can be increased compared to when TS is supplied only to the distribution line 110. Accordingly, the value of V0 detected by the zero-phase voltage sensor 193 can also be increased.

[0110] Therefore, in the example of Fig. 6, larger values ​​of V0s and V0s can be obtained compared to the example of Fig. 5. As a result, the accuracy of ground fault detection by the ground fault determination unit 1022 can be improved.

[0111] 6, as TS2 is supplied to the ground, the second test frequency component of V0 and the second test frequency component of I0 may occur in the power distribution line 110. Therefore, the detection device 100 may determine whether a ground fault has occurred in the power supply system 1 based on at least one of the second test frequency component of V0 and the second test frequency component of I0.

[0112] [Embodiment 2] FIG. 7 shows an example of the configuration of a power supply system 1P and its surroundings according to a second embodiment. FIG. 7 is a diagram paired with FIG. 1. The detection device in the second embodiment is referred to as a detection device 100P. Unlike FIG. 1, FIG. 7 shows multiple power receiving facilities RF. The power supply system 1P includes N power receiving facilities RF, where N is any natural number. In the second embodiment, an example is shown in which N is 2 or more.

[0113] In this specification, the j-th power receiving facility among the N power receiving facilities RF is denoted as power receiving facility RF_j, where j is any natural number satisfying 1≦j≦N. The power receiving facility RF_j may also be referred to as the j-th power receiving facility.

[0114] In the example of Fig. 7, N branch distribution lines 112 are provided in parallel from the distribution line 110 to supply power from the distributed power sources 210 to N power receiving facilities RF, respectively. The branch distribution lines 112 are also referred to as feeder lines. In this specification, the j-th branch distribution line of the N branch distribution lines 112 is referred to as branch distribution line 112_j. The branch distribution line 112_j may also be referred to as the j-th branch distribution line. As shown in Fig. 7, the j-th branch distribution line corresponds to the j-th power receiving facility.

[0115] As indicated by reference numeral 230 in Fig. 7, Fig. 7 illustrates an example in which a short circuit or a ground fault occurs in the Nth branch distribution line. As can be understood from the explanation in the first embodiment, it should be noted that the expression "short circuit or ground fault in the Nth branch distribution line" in this specification does not only mean "a short circuit or a ground fault in the Nth branch distribution line itself," but also generally means "a short circuit or a ground fault in the path of power transmission by the Nth branch distribution line." Therefore, reference numeral 230 in Fig. 7 may also indicate, for example, a short circuit or a ground fault in the Nth power receiving equipment.

[0116] In the example of FIG. 7, the power supply system 1P includes N switches 220. In this specification, the j-th switch of the N switches 220 is referred to as switch 220_j. Switch 220_j may also be referred to as the j-th switch. As shown in FIG. 7, the j-th switch is located on the electrical path of the branch distribution line 112_j. Therefore, the j-th power receiving equipment is connected to the distributed power source 210 via the j-th switch. As will be described later, the conduction state of the j-th switch is controlled by the detection device 100P.

[0117] In the example of FIG. 7 , the N power receiving facilities RF may each have a different power demand pattern. Therefore, the value of the current flowing through the jth branch distribution line may vary depending on the value of j. Therefore, the power supply system 1P includes N current sensors 192. In this specification, the jth current sensor among the N current sensors 192 is referred to as current sensor 192_j. The current sensor 192_j may also be referred to as the jth current sensor. In this specification, the current flowing through the jth branch distribution line is referred to as I_j. The jth current sensor detects I_j. I in the second embodiment is equal to the sum of I_1 to I_N.

[0118] Since the value of the current flowing through the jth branch distribution line may vary depending on the value of j, the value of the zero-phase current flowing through the jth branch distribution line may also vary depending on the value of j. Therefore, the power supply system 1P includes N zero-phase current sensors 194. In this specification, the jth zero-phase current sensor among the N zero-phase current sensors 194 is referred to as zero-phase current sensor 194_j. The zero-phase current sensor 194_j may also be referred to as the jth zero-phase current sensor. In this specification, the zero-phase current flowing through the jth branch distribution line is referred to as I0_j. The jth zero-phase current sensor detects I0_j. I0 in the second embodiment is equal to the sum of I0_1 to I0_N.

[0119] (Configuration example of the detection device 100P) 8 shows an example of the configuration of the detection device 100P. FIG. 8 is a diagram paired with FIG. 2. The control unit in the detection device 100P is referred to as a control unit 102P. The control unit 102P further includes a switching control unit 1024.

[0120] The switching control unit 1024 generates a switching control signal CC_j that controls the conduction state of the j-th switch and supplies the CC_j to the j-th switch. CC_j may also be referred to as the j-th switching control signal. CC in the second embodiment is a generic notation for CC_1 to CC_N.

[0121] In the example of the second embodiment, the logical value "1" of CC_j serves as a turn-on signal that turns on the j-th switch, while the logical value "0" of CC_j serves as a turn-off signal that opens the j-th switch.

[0122] In the second embodiment, the current value acquiring unit 1062 acquires the detection values ​​I_1 to I_N from each of the N current sensors 192. In this manner, the current value acquiring unit 1062 acquires the detection value I_j from the j-th current sensor.

[0123] Then, the zero-phase current value acquiring unit 1072 acquires the detection values ​​I0_1 to I0_N from each of the N zero-phase current sensors 194. In this manner, the zero-phase current value acquiring unit 1072 acquires the detection value I0_j from the j-th zero-phase current sensor.

[0124] In the second embodiment, the first derivation unit 1081 derives a current signal Is_j indicating the inspection frequency component of I_j based on the time-series data of the detection value of I_j supplied from the current value acquisition unit 1062. Is in the second embodiment is equal to the sum of Is_1 to Is_N.

[0125] The second derivation unit 1082 then derives a current signal I0s_j indicating the inspection frequency component of I0_j based on the time-series data of the detection value of I0_j supplied from the zero-phase current value acquisition unit 1072. I0s in the second embodiment is equal to the sum of I0s_1 to I0s_N.

[0126] (Example of processing flow in detection device 100P) Fig. 9 is a flowchart illustrating the flow of processing in the detection device 100P. Fig. 9 is a diagram paired with Fig. 4. S11 and S17 in Fig. 9 are similar to S1 and S7 in Fig. 4, respectively, and therefore will not be described.

[0127] In step S12 following step S11, the control unit 102P executes an inspection process for all of the N branch distribution lines 112. The specific contents of the inspection process will be described later with reference to FIG.

[0128] Next, in step S13, the control unit 102P determines whether a short circuit or a ground fault has occurred in all of the N branch distribution lines 112. The determination process in step S13 is performed based on the result of the inspection process in step S12. Specifically, the determination process in step S13 is performed based on the logical values ​​of CC_1 to CC_N determined as the result of the inspection process in step S12.

[0129] If the answer to step S13 is YES, that is, if a short circuit or a ground fault is detected in all of the N branch distribution lines 112, the process proceeds to step S14. As will be understood from the description of Fig. 10 below, if a short circuit or a ground fault is detected in all of the N branch distribution lines 112, the logical values ​​of all of CC_1 to CC_N become 0.

[0130] In step S14, the independent operation determination unit 1023 outputs SG3=0. In the example of the second embodiment, it is assumed that the independent operation determination unit 1023 is set to output SG3=0 only when all the logical values ​​of CC_1 to CC_N are 0. In other words, the independent operation determination unit 1023 prohibits independent operation of the distributed power source 210 only when all the logical values ​​of CC_1 to CC_N are 0. Then, the process returns to step S11. In the example of FIG. 9, the processes of S11 to S14 are repeated until step S13 becomes NO.

[0131] On the other hand, if the result of step S13 is NO, that is, if a short circuit or a ground fault has been detected in 0 to (N-1) of the N branch distribution lines 112, the process proceeds to step S15.

[0132] In this specification, the branch distribution line in which a short circuit or a ground fault has been detected among the N branch distribution lines 112 is referred to as the branch distribution line of interest. Among the N power receiving facilities RF, the power receiving facility corresponding to the branch distribution line of interest is referred to as the power receiving facility of interest. Furthermore, among the N switches 220, the switch corresponding to the branch distribution line of interest is referred to as the switch of interest.

[0133] In step S15, the switching control unit 1024 identifies a target switch based on the result of the inspection process in step S12. In this case, the switching control unit 1024 supplies a switching control signal as a turn-off signal to the target switch. In this way, the switching control unit 1024 opens the target switch. This makes it possible to prevent a short-circuit current or a ground fault current from flowing through the target power receiving equipment.

[0134] 7 illustrates a case where a short circuit or a ground fault occurs in the Nth branch distribution line. Therefore, in this example, the switching control unit 1024 identifies the Nth switch as the target switch.

[0135] In this case, the switching control unit 1024 sets the logical value of the Nth switching signal to CC_N=0. Then, the switching control unit 1024 supplies CC_N as a turn-off signal to the Nth switch, thereby opening the Nth switch. This makes it possible to prevent a short-circuit current or a ground fault current from flowing to the Nth power receiving equipment, which is the power receiving equipment of interest.

[0136] Next, in step S16, the independent operation determination unit 1023 permits independent operation of the dispersed power source 210. In the second embodiment, the independent operation determination unit 1023 is configured to supply SG3=1 as a start-up signal to the dispersed power source 210 when the target switch is opened. Then, the process proceeds to step S17.

[0137] Fig. 10 is a flowchart illustrating the flow of an inspection process for the branch distribution line 112 in embodiment 2. Specifically, Fig. 10 illustrates the flow of the inspection process in step S12 in Fig. 9. Before the process in Fig. 10 starts, it is assumed that all of the N switches 220 are in an open state.

[0138] First, in step S21, the control unit 102P initializes a counter value j. In the example of Fig. 10, the control unit 102P sets j to 1, which is the initial value.

[0139] In step S22, the switching control unit 1024 sets the logical value of the j-th switching signal to CC_j = 1. Then, the switching control unit 1024 supplies CC_j as a turn-on signal to the j-th switch, thereby closing the j-th switch.

[0140] In this way, the switching control unit 1024 turns on the j-th switch by supplying a turn-on signal to the j-th switch. In the example of Fig. 10, the initial value of j is 1, so the switching control unit 1024 first turns on the first switch by supplying CC_1 as a turn-on signal to the first switch.

[0141] In step S23, the first acquisition unit 106 acquires V from the voltage sensor 191 and acquires I_j from the j-th current sensor 192. Next, the first derivation unit 1081 derives Vs based on V and derives Is_j based on I_j.

[0142] In step S24, the second acquisition unit 107 acquires V0 from the zero-phase voltage sensor 193 and acquires I0_j from the j-th zero-phase current sensor. Next, the second derivation unit 1082 derives V0s based on V0 and derives I0s_j based on I0_j.

[0143] In step S25, the control unit 102P detects whether a short circuit or a ground fault has occurred in the j-th branch distribution line. As can be understood from the description of the first embodiment, the short circuit determination unit 1021 may determine whether a short circuit has occurred in the j-th branch distribution line based on at least one of Vs and Is_j. Then, the ground fault determination unit 1022 may determine whether a ground fault has occurred in the j-th branch distribution line based on at least one of V0s and I0s_j.

[0144] If the result of step S25 is YES, i.e., if a short circuit or a ground fault is detected in the j-th branch distribution line, the process proceeds to step S26. In step S26, the switching control unit 1024 identifies the j-th branch distribution line as the target branch distribution line. Then, the switching control unit 1024 identifies the j-th switch as the target switch.

[0145] In this case, the switching control unit 1024 sets the logical value of the j-th switching signal corresponding to the j-th switch, which is the target switch, to CC_j=0. Then, the switching control unit 1024 supplies CC_j as a turn-off signal to the j-th switch, thereby opening the j-th switch. Then, the process proceeds to step S27.

[0146] On the other hand, if the answer to step S25 is NO, i.e., if neither a short circuit nor a ground fault is detected in the j-th branch distribution line, the j-th branch distribution line can be said to be healthy. Therefore, unlike the case where the answer to step S25 is YES, there is no need to open the j-th switch. Therefore, if the answer to step S25 is NO, the process proceeds to step S27.

[0147] In step S27, control unit 102P counts up j by 1. Next, in step S28, control unit 102P determines whether j has reached the maximum value N. If the answer is NO in step S28, that is, if j has not reached N, the process returns to step S22. Thus, in the example of FIG. 10, the processes of S21 to S28 are repeated until the answer is YES in step S28.

[0148] On the other hand, if the result of step S28 is YES, that is, if j has reached N, the process in Fig. 10 ends. By executing the series of processes in Fig. 10, it is determined whether or not each branch distribution line from the first branch distribution line to the Nth branch distribution line is the target branch distribution line.

[0149] (Effects of the second embodiment) According to the second embodiment, it is possible to identify in which of the first to Nth branch distribution lines a short circuit or a ground fault has occurred. That is, according to the second embodiment, it is possible to identify in more detail the location in the power supply system where a short circuit or a ground fault has occurred. Therefore, the second embodiment contributes to further speeding up recovery from an abnormality in the power supply system.

[0150] Additionally, according to the second embodiment, even if a short circuit or a ground fault occurs in some of the first to Nth branch distribution lines, as long as no short circuit or ground fault occurs in any of the first to Nth branch distribution lines, the distributed power sources 210 can be permitted to operate independently. Specifically, if the number of branch distribution lines of interest is less than N, the switch of interest can be opened and then the distributed power sources 210 can be started up.

[0151] Therefore, according to the second embodiment, power can be supplied from the distributed power source 210 to the power receiving facilities other than the target power receiving facility among the first to Nth power receiving facilities. Therefore, the second embodiment provides an even greater advantage to the consumers who receive power supply from the power supply system.

[0152] [Software implementation example] The functions of the power supply system 1·1P (hereinafter referred to as the "device" for convenience) can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly each part included in the detection device 100·100P).

[0153] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments.

[0154] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0155] Some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of one aspect of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0156] The processes described in the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may run on the control device or on another device (for example, an edge computer or a cloud server).

[0157] 〔summary〕 A detection device according to a first aspect of the present invention is a detection device that supplies three-phase AC power to power receiving equipment through a distribution line and detects the occurrence of a fault in a power supply system that has a distributed power source connectable to a power grid. When the distributed power source is disconnected from the power grid, the detection device supplies an inspection signal to the distribution line having an inspection frequency that is different from the commercial frequency of the power grid, and determines whether a short circuit has occurred in the power supply system based on at least one of an inspection frequency component of a voltage of a specified phase in the distribution line and an inspection frequency component of a current of the specified phase in the distribution line that are generated when the inspection signal is supplied to the distribution line, and determines whether a ground fault has occurred in the power supply system based on at least one of an inspection frequency component of a zero-phase voltage in the distribution line and an inspection frequency component of a zero-phase current in the distribution line that are generated when the inspection signal is supplied to the distribution line.

[0158] In the detection device of aspect 2 of the present invention, in aspect 1, when the distributed power source is disconnected from the power grid, the detection device may start up the distributed power source based on the determination result of whether a short circuit has occurred in the power supply system and the determination result of whether a ground fault has occurred in the power supply system.

[0159] In the detection device according to aspect 3 of the present invention, in aspect 1 or 2, when the distributed power source is disconnected from the power grid, the detection device may further supply a second inspection signal having a second inspection frequency different from the commercial frequency to the ground.

[0160] In the detection device according to a fourth aspect of the present invention, in the third aspect, the second inspection frequency may be different from the inspection frequency.

[0161] A detection device according to a fifth aspect of the present invention may, in the third or fourth aspect, determine whether or not a ground fault has occurred in the power supply system based further on at least one of a second inspection frequency component of the zero-phase voltage in the distribution line and a second inspection frequency component of the zero-phase current in the distribution line, which are generated when the second inspection signal is supplied to the ground when the distributed power source is disconnected from the power grid.

[0162] In a detection device according to aspect 6 of the present invention, in any one of aspects 1 to 5, the distributed power source may be capable of supplying the power to N power receiving equipment respectively connected to N branch distribution lines branching in parallel from the distribution line, and the power supply system may include N switches located on each electrical path of the N branch distribution lines, where N may be a natural number greater than or equal to 2, and when the distributed power source is disconnected from the power system, the detection device may identify a target branch distribution line among the N branch distribution lines, which is the branch distribution line in which a short circuit or a ground fault has occurred, and if the number of target branch distribution lines is less than N, may open a target switch among the N switches, which is the switch corresponding to the target branch distribution line, and then start up the distributed power source.

[0163] A power supply system according to a seventh aspect of the present invention may include the detection device according to any one of the first to sixth aspects and the distributed power source.

[0164] A detection method according to an eighth aspect of the present invention is a detection method for detecting the occurrence of a fault in a power supply system that supplies three-phase AC power to power receiving equipment through a distribution line and includes a distributed power source connectable to a power grid, and includes the steps of: supplying an inspection signal having an inspection frequency different from the commercial frequency of the power grid to the distribution line while the distributed power source is disconnected from the power grid; determining whether or not a short circuit has occurred in the power supply system based on at least one of an inspection frequency component of a voltage of a specified phase in the distribution line and an inspection frequency component of a current of the specified phase in the distribution line that are generated as the inspection signal is supplied to the distribution line; and determining whether or not a ground fault has occurred in the power supply system based on at least one of an inspection frequency component of a zero-phase sequence voltage in the distribution line and an inspection frequency component of a zero-phase sequence current in the distribution line that are generated as the inspection signal is supplied to the distribution line.

[0165] [Additional Notes] One aspect of the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of one aspect of the present invention. [Explanation of symbols]

[0166] 1,1P power supply system 100,100P detection device 102,102P control unit 1021 Short circuit determination unit 1022 Ground fault detection unit 1023 Self-sustaining operation determination unit 1024 Switching control section 110 Power Distribution Line 112, 112_1~112_N Branch distribution lines 191 Voltage Sensor 192, 192_1 to 192_N Current Sensor 193 Zero-phase voltage sensor 194, 194_1~194_N Zero-phase current sensor 210 Distributed power generation 220, 220_1~220_N Switches SYS power system CB circuit breaker RF, RF_1 to RF_N power receiving equipment TS test signal TS2 Second test signal

Claims

1. A detection device that supplies three-phase AC power to power receiving equipment through a distribution line and detects the occurrence of a fault in a power supply system that includes a distributed power source connectable to a power grid, In a state in which the distributed power source is disconnected from the power grid, The detection device includes: supplying an inspection signal having an inspection frequency different from a commercial frequency of the power system to the distribution line; determining whether or not a short circuit has occurred in the power supply system based on at least one of an inspection frequency component of a voltage of a predetermined phase in the distribution line and an inspection frequency component of a current of the predetermined phase in the distribution line, which are generated when the inspection signal is supplied to the distribution line; a detection device that determines whether or not a ground fault has occurred in the power supply system based on at least one of an inspection frequency component of a zero-phase sequence voltage in the distribution line and an inspection frequency component of a zero-phase sequence current in the distribution line, which are generated when the inspection signal is supplied to the distribution line.

2. In a state in which the distributed power source is disconnected from the power grid, The detection device includes: A determination result as to whether a short circuit has occurred in the power supply system; and The detection device according to claim 1 , wherein the distributed power sources are activated based on a determination result of whether or not a ground fault has occurred in the power supply system.

3. In a state in which the distributed power source is disconnected from the power grid, The detection device according to claim 1 , further comprising: a second test signal having a second test frequency different from the power frequency, the second test signal being applied to the ground.

4. The detection device of claim 3 , wherein the second test frequency is different from the test frequency.

5. In a state in which the distributed power source is disconnected from the power grid, The detection device includes:

4. The detection device according to claim 3, wherein whether or not a ground fault has occurred in the power supply system is determined further based on at least one of a second test frequency component of a zero-phase sequence voltage in the distribution line and a second test frequency component of a zero-phase sequence current in the distribution line, which are generated when the second test signal is supplied to the ground.

6. the distributed power source is capable of supplying the power to N power receiving facilities connected to N branch distribution lines branching in parallel from the distribution line, the power supply system includes N switches located on respective electric paths of the N branch distribution lines; N is a natural number greater than or equal to 2, In a state in which the distributed power source is disconnected from the power grid, The detection device includes: Identifying a target branch distribution line among the N branch distribution lines, which is the branch distribution line in which a short circuit or a ground fault has occurred; 2. The detection device according to claim 1, wherein, when the number of the target branch distribution line is less than N, the detection device opens a target switch that corresponds to the target branch distribution line among the N switches, and then starts up the distributed power source.

7. The detection device according to claim 1 ; A power supply system comprising the distributed power source.

8. A detection method for detecting the occurrence of a fault in a power supply system that supplies three-phase AC power to a power receiving facility through a distribution line and includes a distributed power source connectable to a power grid, the method comprising: In a state in which the distributed power source is disconnected from the power grid, supplying an inspection signal having an inspection frequency different from a commercial frequency of the power grid to the power distribution line; determining whether a short circuit has occurred in the power supply system based on at least one of an inspection frequency component of a voltage of a predetermined phase in the distribution line and an inspection frequency component of a current of the predetermined phase in the distribution line, which are generated when the inspection signal is supplied to the distribution line; determining whether or not a ground fault has occurred in the power supply system based on at least one of an inspection frequency component of a zero-phase sequence voltage in the distribution line and an inspection frequency component of a zero-phase sequence current in the distribution line, which are generated as the inspection signal is supplied to the distribution line.

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