Ground fault cause estimation system

Abstract

To provide a ground fault cause estimation system that enables estimation of the equipment subjected to a ground fault and its reason, that allows faster and more precise estimation of the cause of the ground fault, and that facilitates easier response to the cause of the ground fault.SOLUTION: A ground fault cause estimation system 1 comprises a computer 6 including a computer communication section 46, an interface 47, a computer memory section 44, and a computer control section 48. The computer communication section 46 can receive a zero-phase current signal that represents zero-phase current. The interface 47 can receive an electromagnetic wave signal that represents an electromagnetic wave generated due to partial discharge of electrical equipment. The computer control section 48 estimates a cause of a ground fault on the basis of a zero-phase current signal waveform representing temporal change of the zero-phase current signal and an electromagnetic wave signal waveform representing temporal change of the electromagnetic wave signal.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a ground fault cause estimation system, which is a system for estimating the cause of a ground fault. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 11-352177 (Patent Document 1) discloses a method for identifying partial discharge-degraded equipment, which identifies degradation of electrical equipment without causing a power outage to a consumer. In this method, insulation deterioration of electrical equipment installed in power equipment such as high-voltage consumer power receiving equipment is identified by detecting partial discharge signals. A first detection position for the partial discharge signal is selected inside the power equipment, and a second detection position for the partial discharge signal is selected outside the power equipment. Then, insulation deterioration of the electrical equipment is identified by comparing the partial discharge signals detected at the first and second detection positions. Note that this method can also identify contact of other objects, such as animals and plants, with the electrical equipment. In detecting partial discharge signals at the first detection position, high-frequency current transformers are attached to the ends of the service cables inside the high-voltage consumer power receiving equipment for all three phases, and the high-frequency spectrum or waveform of the zero-phase current signal is detected. In detecting partial discharge signals at the second detection position, high-frequency current transformers with the same characteristics as the above-mentioned high-frequency current transformers are attached to the ends of the service cables outside the high-voltage consumer power receiving equipment for all three phases, and the high-frequency spectrum or waveform of the zero-phase current signal is detected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-352177 Summary of the Invention [Problem to be solved by the invention]

[0004] The above method allows a fault responder, who responds to faults such as deterioration, to distinguish whether the fault is due to equipment within the power receiving equipment or external noise. However, to identify the deteriorated equipment in the power receiving equipment, the fault responder must repeatedly measure the discharge signals at each phase and each part of the high-voltage bus bar within the power receiving equipment until the fault is identified, except in cases where the fault is clearly visible, such as continuous smoke generation. The fault responder must also check the high-frequency current transformers at each phase and each part of the high-voltage bus bar. Clearly visible cases, such as smoke generation, are rare among ground faults. Furthermore, smoke generation can lead to a fire and escalate into a dangerous situation. Therefore, it is preferable to discover the fault before a situation that generates smoke occurs. Furthermore, with the above method, the person responding to the fault cannot grasp the estimated cause of deterioration of the electrical equipment in advance, so the person responding to the fault must measure the discharge signals at each phase and each part of the high-voltage bus in the power receiving equipment without any guidelines, except when the discharge signals are clearly visible. Recently, the number of ground faults has been gradually increasing, while securing personnel to deal with the faults has become difficult due to a shortage of personnel, etc. Furthermore, personnel who deal with faults are requested by those involved in the power receiving equipment to quickly identify the cause of the fault, but identifying the cause of the fault takes time if they are to do so without any guidelines.

[0005] Therefore, one of the main objects of the present invention is to provide a ground fault cause estimation system that can estimate the equipment in which a ground fault has occurred. The equipment may include continuous structures such as electric wires and high-voltage cables. The equipment may also include insulating supports such as insulators. Estimating the equipment in which a ground fault has occurred may include estimating the part of the equipment in which the fault has occurred. Furthermore, another main object of the present invention is to provide a ground fault cause estimation system that is capable of estimating the reason why a ground fault has occurred. In addition, yet another main object of the present invention is to provide a ground fault cause estimation system that can estimate the cause of a ground fault more quickly and with higher accuracy. Another main object of the present invention is to provide a ground fault cause estimation system that can more easily address the cause of a ground fault. [Means for solving the problem]

[0006] This specification discloses a ground fault cause estimation system. This ground fault cause estimation system may be a system that estimates the cause of a ground fault, which is a failure of electrical equipment due to a ground fault. The ground fault cause estimation system may include a computer. The computer may have a computer receiving unit. The computer may have a computer control unit. The computer receiving unit may be capable of receiving a zero-phase current signal that is a signal indicating a zero-phase current. The computer receiving unit may be capable of receiving an electromagnetic wave signal that is a signal indicating electromagnetic waves generated by partial discharge of the electrical equipment. The computer control unit may estimate the cause of the ground fault based on a zero-phase current signal waveform that is a waveform that indicates a change over time in the zero-phase current signal. The computer control unit may estimate the cause of the ground fault based on an electromagnetic wave signal waveform that is a waveform that indicates a change over time in the electromagnetic wave signal. [Effects of the Invention]

[0007] One of the main effects of the present invention is to provide a ground fault cause estimation system that can estimate the equipment in which a ground fault has occurred. Furthermore, another major effect of the present invention is to provide a ground fault cause estimation system that is capable of estimating the reason why a ground fault has occurred. In addition, yet another major effect of the present invention is to provide a ground fault cause estimation system that can estimate the cause of a ground fault more quickly and with higher accuracy. Furthermore, one of the other main effects of the present invention is that a ground fault cause estimation system is provided that can more easily address the cause of a ground fault. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a schematic diagram of a part of a ground fault cause estimation system according to an embodiment of the present invention, and private equipment as an example of an estimation target. [Figure 2] 1 is a block diagram of a ground fault cause estimation system according to an embodiment of the present invention, and a portion of private equipment. [Figure 3] FIG. 3 is a block diagram showing the zero-phase current measuring device in FIG. 2. [Figure 4] FIG. 4 is a block diagram showing an AD conversion board and an adapter in FIG. 3. [Figure 5] FIG. 3 is a block diagram showing the computer in FIG. 2. [Figure 6] 2 is a flowchart showing an example of the operation of the ground fault cause estimation system in FIG. 1. [Figure 7] 7 is a part of a flowchart showing details of the estimation of the cause of a failure in FIG. 6. [Figure 8] 7 is another part of the flowchart showing the details of the estimation of the cause of the failure in FIG. 6. [Figure 9] 6A and 6B are schematic diagrams showing an example of a zero-phase current signal waveform image and an example of a juxtaposed image displayed on the computer display unit of FIG. 5. [Figure 10] 6A and 6B are schematic diagrams showing another example of a zero-phase current signal waveform image and another example of a juxtaposed image displayed on the computer display unit of FIG. 5. [Figure 11] 7A and 7B are schematic diagrams showing still another example of a zero-phase current signal waveform image and still another example of a juxtaposed image displayed on the computer display unit of FIG. 5. [Figure 12] 6A and 6B are schematic diagrams showing another example of a zero-phase current signal waveform image and another example of a juxtaposed image displayed on the computer display unit of FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention and modifications thereof will be described with reference to the accompanying drawings. The present invention is not limited to the following embodiments and modifications.

[0010] FIG. 1 is a schematic diagram of a part of the ground fault cause estimation system 1 of this embodiment and a private installation PUF as an example of an estimation target. The ground fault cause estimation system 1 estimates the cause of a ground fault in a private equipment PUF. A ground fault is a fault caused by a ground fault. The cause of the ground fault includes the type of faulty device, which is the electrical device in the private equipment PUF that has failed, and the reason for the failure. The cause of the ground fault may include only either the type of faulty device or the reason for the fault, or may include other items.

[0011] The private facility PUF is a facility that allows consumers to receive high voltage electricity from the general electricity transmission and distribution company's facilities, and is located on the private side of the responsibility boundary REB. The private facility PUF includes a utility pole facility POL and a high-voltage power receiving facility HVR.

[0012] The utility pole installation POL includes a utility pole P, a plurality of cross arms A, an air load switch PAS, a cable head H1, a directional earth fault relay DGR, and a control cable C.

[0013] The utility pole P is erected on the ground surface GLS. Each cross arm A is fixed to a utility pole P and extends horizontally.

[0014] The air load switch PAS is a high voltage AC load switch for a directional earth fault relay DGR, and includes a switch SWR and a zero-phase sequence voltage detector ZPD. The earth fault directional relay DGR is a device that controls the air load break switch PAS. The earth fault directional relay DGR is fixed to the utility pole P near the ground GLS. The air load switch PAS is fixed to the utility pole P via an arm A. The air load switch PAS is connected to the service line LIL (typically three lines instead of one in Figure 1) of the distribution line PL, and is located adjacent to the responsibility demarcation point. More specifically, the responsibility demarcation point is the power supply side connection point of the switch SWR. The air load break switch PAS and its control device, the earth fault directional relay DGR, are designed to confine power outages and other disturbances to the private equipment PUF even if a fault occurs in the high-voltage power receiving equipment HVR, preventing a cascade of faults to the distribution line PL side (other consumers), and to maintain power reception at the private high-voltage power receiving equipment HVR without opening the circuit in the event of a fault current from other consumers. The earth fault directional relay DGR prevents the air load break switch PAS from malfunctioning (a contagious fault) due to the inflow of fault current from other consumers. The earth fault directional relay DGR is capable of Storage Over Current Ground (SOG) operation.

[0015] The cable head H1 is fixed to the utility pole P via a cross arm A that is different from the cross arm A of the air load switch PAS. The cable head H1 is located on the high-voltage power receiving equipment HVR side of the air load switch PAS, and is connected to the air load switch PAS by high-voltage wiring HC1. Generally, there are three high-voltage wirings HC1.

[0016] The control cable C is interposed between the air load switch PAS and the earth fault directional relay DGR. The control cable C transmits control signals such as various commands communicated between the air load switch PAS and the earth fault directional relay DGR, as well as earth fault currents.

[0017] The high-voltage power receiving equipment HVR is connected to the distribution line PL via the air load break switch PAS. The high-voltage power receiving equipment HVR has a housing HO that houses various electrical equipment. A high-voltage cable HC2 is drawn into the housing HO of the high-voltage power receiving equipment HVR from a cable head H1. The high-voltage cable HC2 is generally a bundle of three-phase conductors, and three high-voltage wires HC1 are gathered together at the cable head H1.

[0018] A zero-phase current transformer ZCT is installed in the high-voltage cable HC2 drawn into the high-voltage power receiving equipment HVR. The zero-phase current transformer ZCT detects earth fault current. The zero-phase current transformer ZCT may be disposed in another location such as inside the air load switch PAS.

[0019] The earth fault directional relay DGR issues an opening command to the switch SWR when it detects an earth fault current equal to or greater than a set value based on the phase relationship between the earth fault current detected by the zero-phase current transformer ZCT and the zero-phase sequence voltage detected simultaneously with the earth fault current by the zero-phase sequence voltage detector ZPD of the air load switch PAS, and the phase relationship of the zero-phase sequence voltage indicates an earth fault in the private equipment PUF. The switch SWR performs an opening operation based on the opening command, and separates the private equipment PUF from the distribution line PL side. The air load switch PAS and earth fault directional relay DGR will not open even if a fault current above a set value is detected if the phase relationship of the zero-phase sequence voltage indicates a ground fault in another consumer based on the detection of the directionality of the ground fault current. Therefore, a private equipment PUF equipped with an air load switch PAS and earth fault directional relay DGR will not open due to a fault current from another consumer (outside the premises), preventing the occurrence of a cross-connect fault and unnecessary power outages.

[0020] The high-voltage cable HC2 passes through the zero-phase current transformer ZCT, passes through the cable head H2 of the high-voltage power receiving equipment HVR, and reaches the disconnector DS and power fuse F. From the power fuse F, multiple (three) in-facility cables EC1 to EC3 extend. The first in-facility cable EC1 is connected to a low-voltage switchboard LVS via an instrument transformer VT. The low-voltage switchboard LVS has a protection relay (not shown). The second intra-facility cable EC2 passes through a transformer TN and leads to a low voltage switchboard LVS. The third intra-facility cable EC3 is connected to a capacitor CA.

[0021] FIG. 2 is a block diagram of the ground fault cause estimation system 1 and a portion of the private installation PUF. The ground fault cause estimation system 1 includes a partial discharge sensor TEVS, a power supply voltage measurement device 2, a zero-phase current measurement device 4, and a computer 6. The ground fault cause estimation system 1 may also include at least one of a zero-phase current transformer ZCT and a voltage detector CM. The ground fault cause estimation system 1 may also be composed of only the power supply voltage measurement device 2, the zero-phase current measurement device 4, and the computer 6. Furthermore, at least two of the power supply voltage measurement device 2, the zero-phase current measurement device 4, and the computer 6 may be integrated. At least one of the power supply voltage measurement device 2, the zero-phase current measurement device 4, and the computer 6 may be distributed across two or more devices.

[0022] Power from substation SS is sent to high-voltage power receiving equipment HVR via distribution line PL, which has resistance RE.

[0023] The voltage detector CM detects the AC voltage of the distribution line PL. Here, the AC voltage of the distribution line PL is the voltage of the commercial power supply, i.e., the commercial power supply voltage. Here, the frequency of the commercial power supply voltage is 60 Hz. Here, the voltage detector CM is a relay. Note that the voltage detector CM may be a zero-phase current transformer similar to the zero-phase current transformer ZCT of the high-voltage power receiving equipment HVR. Also, the voltage detector CM may be placed between the resistance RE and the high-voltage power receiving equipment HVR, rather than between the substation SS and the resistance RE. Furthermore, the frequency of the commercial power supply voltage may be another value, such as 50 Hz. The power supply voltage measuring device 2 measures the AC voltage of the power distribution line PL, that is, the commercial power supply voltage, via a voltage detector CM, and generates a commercial power supply voltage signal indicative of the commercial power supply voltage. The power supply voltage measuring device 2 has a power supply voltage measuring device communication unit capable of communication. The partial discharge sensor TEVS is connected to the Internet 20 via the power supply voltage measuring device communication unit. Note that the power supply voltage measuring device 2 may be connected to at least one of a LAN (Local Area Network), a mobile phone network, and a dedicated line in order to be able to communicate with the Internet 20, instead of or in addition to the Internet 20.

[0024] FIG. 3 is a block diagram of the zero-phase current measuring device 4. The zero-phase current measuring device 4 includes a single-board computer 10, an AD conversion board 12 as an analog-to-digital conversion unit, and an adapter 14. The AD conversion is analog-to-digital conversion. The single-board computer 10 is a computer consisting of a single board. The single-board computer 10 includes a CPU 22 as a single-board computer control unit, a memory 24 as a storage unit, a DMAC 26, an interface 28, and a communication unit 29. At least one of the CPU 22, memory 24, DMAC 26, interface 28, and communication unit 29 may be integrated into a single chip. The integration of the CPU 22 and other components into a single chip is called a SoC (System on Chip). The zero-phase current measurement device 4 may also include other processing units such as a GPU (Graphics Processing Unit). Alternatively, the DMAC 26 may be omitted from the zero-phase current measurement device 4. Parts of the single-board computer 10, such as the communication unit 29, may be mounted on separate boards. Additionally, the single-board computer 10 and the AD conversion board 12 may be integrated into a single board. In such an integration, for example, the CPU 22 as a single-board computer control unit and the control unit 30 of the AD conversion board 12 may be integrated and regarded as a single control unit of the zero-phase current measurement device 4. Alternatively, the single-board computer 10 and the AD conversion board 12 may be partially or entirely divided into three or more parts.

[0025] The CPU 22 is a central processing unit that controls the memory 24 , the DMAC 26 , and the interface 28 . The memory 24 stores various types of information. The DMAC 26 is a direct memory access controller. The interface is a part that connects the single-board computer 10 to an external device, and is an SPI (Serial Peripheral Interface) in this case. The single-board computer 10 is connected to the AD conversion board 12 at the interface . As indicated by the two-dot chain line in FIG. 3, the DMAC 26 transmits information from the interface 28 directly to the memory 24 without going through a command from the CPU 22, and stores the information in the memory 24 without using the processing power of the CPU 22. The communication unit 29 is a part that connects the zero-phase current measuring device 4 to external devices so that they can communicate with each other. The communication unit 29 is connected to the Internet 20. Note that the communication unit 29 may be connected to at least one of a LAN, a mobile phone network, and a dedicated line so that it can communicate with each other, instead of the Internet 20 or in addition to the Internet 20. The interface 28 and the communication unit 29 may be integrated. Furthermore, the communication unit 29 may be capable of wireless communication or wired communication.

[0026] FIG. 4 is a block diagram of the AD conversion board 12 and the adapter 14. The AD conversion board 12 includes a control unit 30, a power supply circuit 32, a differential amplifier 34, a first wiring W1, a second wiring W2, a third wiring W3, a fourth wiring W4, a shunt resistor 35, an AD converter 36, and an interface 38.

[0027] The control unit 30 controls various parts of the AD conversion board 12 . The power supply circuit 32 supplies power to various parts of the AD conversion board 12. The voltage of the power is DC, which maintains a predetermined value. The predetermined value is, for example, 12V (volts).

[0028] The differential amplifier 34 is connected to the zero-phase-sequence current transformer ZCT. More specifically, the differential amplifier 34 is connected to a first lead wire L1 and a second lead wire L2 extending from the zero-phase-sequence current transformer ZCT. The first lead wire L1 is connected to the differential amplifier 34 via a first wiring W1. The second lead wire L2 is connected to the differential amplifier 34 via a second wiring W2. Here, the second lead wire L2 is grounded via the ground G. The third wiring W3 and the fourth wiring W4 coming out of the differential amplifier 34 are each connected to an AD converter 36. The differential amplifier 34 amplifies the voltage between the first wiring W1 and the second wiring W2 and transmits it to the AD converter 36 as a voltage between the third wiring W3 and the fourth wiring W4. In other words, the differential amplifier 34 amplifies the signal between the first wiring W1 and the second wiring W2 and transmits it to the AD converter 36. The differential amplifier 34 operates within a predetermined voltage range. The predetermined voltage is, for example, 5 V for the third wiring W3 relative to the fourth wiring W4. The shunt resistor 35 is interposed between the first wiring W1 and the second wiring W2. The shunt resistor 35 converts the current flowing from the first lead wire L1 and the second lead wire L2 into a voltage. The resistance value of the shunt resistor 35 is adjusted according to the range of the current flowing through the shunt resistor 35, i.e., the secondary current of the zero-phase current transformer ZCT, when the gain of the differential amplifier 34 and the analog input range of the AD converter 36 are determined. Appropriately adjusting the resistance value of the shunt resistor 35 suppresses waveform clipping in the waveform showing the time-dependent change in the current value of the zero-phase current transformer ZCT. This waveform is more realistic and suitable for estimating the cause of a ground fault. Waveform clipping is a phenomenon in which the absolute value of the current value in the waveform showing the time-dependent change in the current value of the zero-phase current transformer ZCT is kept below a predetermined threshold, differing from the actual value. The shunt resistor 35 may be a variable resistor whose resistance value is changeable in order to more appropriately accommodate the current transformation ratios of various zero-phase current transformers ZCT.

[0029] The AD converter 36 converts the analog voltage change between the third wiring W3 and the fourth wiring W4 into a digital voltage change. In other words, the AD converter 36 converts the analog signal between the third wiring W3 and the fourth wiring W4 into a digital signal. The interface 38 is connected to the interface 28 of the single-board computer 10. The control unit 30 transmits the digital signal of the AD converter 36 to the single-board computer 10 via the interface 38.

[0030] The adapter 14 is connected to the power supply circuit 32 of the AD conversion board 12. The adapter 14 is connected to a commercial AC power supply, converts the commercial power supply into a DC of a predetermined value, and supplies the DC to the power supply circuit 32. The adapter 14 may be integrated into the power supply circuit 32. An isolation transformer may be disposed between the adapter 14 and the commercial power supply. The provision of such an isolation transformer suppresses malfunction of the AD conversion board 12 due to common-mode current. Common-mode current is a current of the same phase in the first lead wire L1 and the second lead wire L2, and may be generated by the ground G. Without an isolation transformer, the common-mode current flows through the first and second wires W1 and W2, the differential amplifier 34, the third and fourth wires W3 and W4, the power supply circuit 32, and the adapter 14 in the AD conversion board 12, before reaching the commercial power supply. In contrast, the provision of an isolation transformer eliminates the common-mode current. Furthermore, the common-mode current is also eliminated when an insulating electronic component is disposed on the AD conversion board 12 instead of or in addition to the isolation transformer.

[0031] The partial discharge sensor TEVS is a sensor for measuring partial discharges that detects TEV (Transient Earth Voltage). The partial discharge sensor TEVS generates an electromagnetic wave signal based on a change in capacitance caused by receiving electromagnetic waves generated by partial discharges with a metal plate-shaped electrode, and detects the TEV based on the state of the electromagnetic wave signal. The partial discharge sensor TEVS outputs an electromagnetic wave signal waveform corresponding to the received discharge electromagnetic waves. Note that the partial discharge sensor TEVS may detect the TEV using a means other than the electrode, or may detect the TEV based on a means other than a change in capacitance. The partial discharge sensor TEVS is fixed to the inner surface of the housing HO of the high-voltage power receiving equipment HVR. Note that the partial discharge sensor TEVS may also be fixed to the outer surface of the housing HO of the high-voltage power receiving equipment HVR. The partial discharge sensor TEVS has a partial discharge sensor communication unit capable of communication. The partial discharge sensor TEVS is connected to the Internet 20 via the partial discharge sensor communication unit. Note that the partial discharge sensor TEVS may be connected to at least one of a LAN, a mobile phone network, and a dedicated line in order to be able to communicate with the Internet 20, instead of or in addition to the Internet 20.

[0032] FIG. 5 is a block diagram showing the computer 6. The computer 6 has a computer display unit 40, a computer input unit 42, a computer memory unit 44, a computer communication unit 46 as part of the computer receiving unit, an interface 47 as another part of the computer receiving unit, and a computer control unit 48.

[0033] The computer display unit 40 displays information. For example, the computer display unit 40 is at least one of a display and a lamp. The computer input unit 42 accepts input of information. For example, the computer input unit 42 is at least one of a keyboard and a pointing device. The computer display unit 40 and the computer input unit 42 may be integrated into a touch-sensor display. Computer storage 44 stores information. For example, computer storage 44 may be a random access memory and / or a temporary or non-transitory computer-readable storage medium.

[0034] The computer communication unit 46 communicates information via the Internet 20. For example, the computer communication unit 46 is at least one of wired and wireless communication devices. Note that the computer 6 may be communicatively connected to at least one of a LAN, a mobile phone network, and a dedicated line instead of or in addition to the Internet 20. The interface 47 receives an electromagnetic wave signal from the partial discharge sensor TEVS. The computer communication unit 46 and the interface 47 may be integrated or may be separated into three or more independent parts. The computer control unit 48 controls the computer display unit 40, the computer input unit 42, the computer storage unit 44, and the computer communication unit 46. For example, the computer control unit 48 is a CPU. An estimation program is stored in the computer memory unit 44. The estimation program is executed by the computer control unit 48. An estimation program read from a non-transitory computer-readable storage medium is formed in the computer memory unit 44. The non-transitory computer-readable storage medium records the estimation program. The estimation program has a function of estimating the cause of a failure in the high-voltage power receiving equipment HVR. The estimation program contains a set of instructions that cause the function described below to be performed. Note that the estimation program may be stored in the computer memory unit 44 by a method other than reading from a non-transitory computer-readable storage medium. For example, the estimation program may be non-temporarily formed in the computer memory unit 44 when the computer memory unit 44 is manufactured.

[0035] The computer 6 is communicably connected to the power supply voltage measuring device 2, the zero-phase current measuring device 4, and the partial discharge sensor TEVS via a computer communication unit 46 and the Internet 20. The zero-phase current measuring device 4 is connected to the zero-phase current transformer ZCT. The computer 6 is installed, for example, in an area managed by an organization that inspects private equipment PUFs and responds to faults. At least one of the power supply voltage measuring device 2, the zero-phase current measuring device 4, and the partial discharge sensor TEVS may be connected to the computer 6 directly or via a LAN. Alternatively, at least two of the power supply voltage measuring device 2, the zero-phase current measuring device 4, and the partial discharge sensor TEVS may be connected to an independent communication device on the private equipment PUF side, and the communication device may be connected to the computer 6 via the Internet 20. The communication device may perform part of the processing performed by the computer 6. When all of the power supply voltage measuring device 2, the zero-phase current measuring device 4, and the partial discharge sensor TEVS are connected to the computer 6 directly or via a LAN, the computer 6 may be installed on the private equipment PUF side.

[0036] The power supply voltage measuring device 2 is capable of outputting a commercial power supply voltage signal waveform, which is the waveform of a commercial power supply voltage signal. The commercial power supply voltage signal waveform indicates changes in the commercial power supply voltage over time. The computer 6 is capable of receiving the commercial power supply voltage signal waveform from the power supply voltage measuring device 2. The computer control unit 48 stores the commercial power supply voltage signal waveform received at the interface 47 in the computer storage unit 44. The zero-phase current transformer ZCT is capable of outputting a zero-phase current waveform. The zero-phase current I0 is an in-phase current observed when there is a circuit imbalance due to a ground fault or the like. The zero-phase current waveform indicates the change in the zero-phase current I0 over time. The zero-phase current measuring device 4 is capable of AD converting the zero-phase current waveform and outputting a zero-phase current signal waveform corresponding to the zero-phase current waveform. The computer 6 is capable of receiving the zero-phase current signal waveform from the zero-phase current measuring device 4. The computer control unit 48 stores the zero-phase current signal waveform received by the computer communication unit 46 in the computer memory unit 44. The partial discharge sensor TEVS outputs an electromagnetic wave signal over time, thereby outputting an electromagnetic wave signal waveform that indicates the change in the electromagnetic wave signal over time. The computer 6 can receive the electromagnetic wave signal waveform from the partial discharge sensor TEVS. The computer control unit 48 stores the electromagnetic wave signal waveform received by the computer communication unit 46 in the computer storage unit 44.

[0037] The computer control unit 48 can compare the electromagnetic wave signal waveform with the commercial power voltage signal waveform while matching the time of the electromagnetic wave signal waveform with the time of the commercial power voltage signal waveform in order to determine the phase of the commercial power voltage waveform that corresponds to a specific portion of the electromagnetic wave signal waveform. Furthermore, the computer control unit 48 can compare the electromagnetic wave signal waveform with the zero-phase-sequence current signal waveform to achieve more accurate estimation of the cause of the ground fault. The computer control unit 48 may also compare the electromagnetic wave signal waveform with the zero-phase-sequence current waveform. The computer control unit 48 may also compare the electromagnetic wave signal waveform with the zero-phase-sequence current signal waveform while matching the time of the electromagnetic wave signal waveform with the time of the zero-phase-sequence current signal waveform. The cause of the ground fault is estimated based on integrated processing of the output signals of the zero-phase current transformer ZCT as a sensor for the zero-phase current I0 and the partial discharge sensor TEVS as a sensor for the electromagnetic waves or TEV of partial discharge (Sensor Fusion). The fused sensors may further include a power supply voltage measuring device 2 as a sensor for the commercial power supply voltage signal waveform.

[0038] An example of the operation of such a ground fault cause estimation system 1 will be described below.

[0039] FIG. 6 is a flowchart relating to this operation example. The computer control unit 48, which executes the estimation program, constantly acquires and stores in the computer storage unit 44 for monitoring purposes the zero-phase current signal waveform associated with the zero-phase current transformer ZCT, the electromagnetic wave signal waveform associated with the partial discharge sensor TEVS, and the commercial power voltage signal waveform (step S1). The commercial power voltage signal waveform is compared with the electromagnetic wave signal waveform to determine the phase of the commercial power voltage in the electromagnetic wave signal waveform. The comparison of the commercial power voltage signal waveform with the electromagnetic wave signal waveform is performed while the timing of acquisition of the commercial power voltage signal by the power supply voltage measurement device 2 is synchronized with the timing of acquisition of the electromagnetic wave signal by the partial discharge sensor TEVS. To achieve more accurate synchronization, a synchronization signal transmitter that transmits a synchronization signal to the power supply voltage measurement device 2 and the partial discharge sensor TEVS may be provided independently, or in at least one of the power supply voltage measurement device 2 and the partial discharge sensor TEVS, or in another device. The synchronization may be achieved between the timing of acquisition of the commercial power voltage signal and / or the electromagnetic wave signal and the timing of acquisition of the zero-phase current signal by the zero-phase current measurement device 4. In order to perform the synchronization more accurately, at least two of the power supply voltage measuring device 2, the zero-phase current measuring device 4, and the partial discharge sensor TEVS may be integrated into one device. When a fluctuation of a predetermined threshold or more occurs in at least one of the zero-phase current signal waveform, the electromagnetic wave signal waveform, and the commercial power voltage signal waveform, the computer control unit 48 may store the waveform in the computer storage unit 44. The computer control unit 48 may also erase the stored zero-phase current signal waveform, the electromagnetic wave signal waveform, and the commercial power voltage signal waveform that are older than a predetermined time.

[0040] When the predetermined timing arrives (Yes in step S2), the computer control unit 48 causes the computer display unit 40 to display a zero-phase current signal waveform image WI1, which is an image of the zero-phase current signal waveform relating to the specific time, and a juxtaposed image WI2, which is an image in which the electromagnetic wave signal waveform and the commercial power voltage signal waveform are juxtaposed for comparison (step S3). Examples of the zero-phase current signal waveform image WI1 and the juxtaposed image WI2 are shown in Figures 9 and onwards. On the other hand, if the predetermined timing has not arrived (No in step S2), the computer control unit 48 returns to start and continues step S1. The specified timing and specific time are, for example, the time from the time of power outage to a specified time (e.g., 1 second) after a power outage request is made by a consumer of a private equipment PUF, or the time from the time of power loss information detection to a specified time after a power outage request is made by a general electricity transmission and distribution company equipment, or the time specified by input when the operator of computer 6 makes a specified input to computer input unit 42. The following describes the case where a power outage occurs. Note that, in the event of a power outage, the computer 6 may automatically display on the computer display unit 40 a zero-phase current signal waveform image WI1 and a juxtaposed image WI2 of an electromagnetic wave signal waveform and a commercial power voltage signal waveform for a specific time.

[0041] If the zero-phase current I0 is not detected, and the electromagnetic waves are not detected, and the TEV is not detected (Yes in step S4), the computer control unit 48 determines that the cause of the power outage is at least one of a short-circuit fault, an open-phase fault, a blown fuse, and a breaker operation (step S5). Note that not detecting the zero-phase current I0 may include the zero-phase current I0 being equal to or less than a specific threshold, and non-detection of other items can be similarly changed. On the other hand, if the zero-phase current I0 is detected and the TEV is not detected (No in step S4 and Yes in step S6), the computer control unit 48 determines that the cause of the power outage is at least one of a cable failure and an off-site failure (step S7). On the other hand, if the zero-phase current I0 is detected and the TEV is detected (No in step S4 and No in step S6), the computer control unit 48 determines that the cause of the power outage is a failure of the electrical equipment related to the high-voltage power receiving equipment HVR (step S8) and estimates the cause of the failure (step S9).

[0042] Fig. 7 is a part of a flowchart relating to the details of estimating the cause of a fault. Fig. 8 is another part of the flowchart relating to the details of estimating the cause of a fault, and shows a continuation of Fig. 7. Note that the cause of a fault may be estimated by an operator who views the zero-phase current signal waveform image WI1 and the juxtaposed image WI2.

[0043] As shown in FIG. 9, if the zero-phase current signal waveform after the power outage is continuous, has a uniform amplitude (magnitude of the zero-phase current I0) except for the relatively large inrush current immediately after the power outage, and has a frequency proportional to the commercial power voltage frequency, and if the maximum value M1 in the electromagnetic wave signal waveform after the power outage is located at a time within the phase section P1 from -180° to 0° of the commercial power voltage frequency (Yes in step S11 of FIG. 7), the computer control unit 48 estimates that the cause of the failure is metal contact (step S12). Metal contact occurs when metal comes into contact with electrical equipment in a high-voltage power receiving facility (HVR), such as contact with electrical equipment on a crane truck. If metal contact is the cause, the equipment that has failed is the equipment that has come into contact with metal, and the reason for the failure is metal contact. Therefore, the person responsible for dealing with the failure simply needs to look for metal or electrical equipment that has come into contact with metal. The computer control unit 48 may determine whether a part or all of the portion of the electromagnetic wave signal waveform that is equal to or greater than a predetermined threshold falls within the phase section P1. Such a determination method may also be used appropriately in other cases. Furthermore, the computer control unit 48 may determine the electromagnetic wave signal waveform based on the type of shape of the electromagnetic wave signal waveform, instead of or in addition to determining the phase of the commercial power supply voltage.

[0044] Furthermore, as shown in Fig. 10, if the zero-phase current signal waveform after the power outage is intermittent, has non-uniform amplitude, and has a frequency higher than the commercial power voltage frequency, and if the maximum value M2 in the electromagnetic wave signal waveform after the power outage is located at a time within the phase section P2 of the commercial power voltage frequency from 0° to +180° (No in step S11 of Fig. 7 and Yes in step S13 of Fig. 7), the computer control unit 48 estimates that the cause of the fault is poor insulation of the high-voltage cable (step S14 of Fig. 7). The zero-phase current signal waveform has a needle-like waveform due to its high frequency. Poor insulation of a high-voltage cable indicates that the equipment causing the failure is a high-voltage cable and the cause of the failure is poor insulation, such as water tree deterioration. Water tree deterioration is a phenomenon in which tree-shaped electrical paths form in the insulation of a high-voltage cable. In the case of poor insulation of a high-voltage cable, the person responding to the failure only needs to inspect the high-voltage cable HC2 and other cables in the numerous electrical equipment.

[0045] On the other hand, if the zero-phase current signal waveform after the power outage is continuous, has non-uniform amplitude, and has a frequency higher than the commercial power voltage frequency, and if the maximum value M3 in the electromagnetic wave signal waveform after the power outage is located within the phase interval P3 from +180° to −180° of the commercial power voltage (No in step S13 of FIG. 7 and Yes in step S15 of FIG. 8), the computer control unit 48 estimates that the cause of the fault is discharge in the electrical insulating oil sealed in the electrical equipment, such as the transformer TN or the capacitor CA (step S16 of FIG. 8). The zero-phase current signal waveform has a needle-like waveform due to its high frequency. Furthermore, the zero-phase current signal waveform in the case of discharge in the electrical insulating oil is similar to the zero-phase current signal waveform associated with insulation failure in a high-voltage cable. Since the zero-phase current signal waveform is used as the basis for estimation together with the electromagnetic wave signal waveform, these cases can be distinguished with higher accuracy. To further improve accuracy, the cause of the fault may be estimated to be discharge in the electrical insulating oil by taking into consideration that the integral value of the zero-phase current signal waveform is equal to or greater than a predetermined threshold (high integral value). If the integral value of the zero-phase current signal waveform is equal to or greater than a predetermined threshold, the continuity of the zero-phase current I0 can be taken into consideration with higher accuracy. Discharge in electrical insulating oil indicates that the equipment in which the fault occurred is electrical insulating oil and the cause of the failure is discharge, for example, at least one of an internal failure of a transformer and an internal failure of a capacitor. In the case of discharge in electrical insulating oil, the person responding to the fault should inspect the electrical equipment that uses electrical insulating oil, such as the transformer TN and capacitor CA.

[0046] On the other hand, if the zero-phase current signal waveform after the power outage is continuous, the amplitude gradually increases, and the frequency is proportional to the commercial power voltage frequency, as shown in Figure 12, and the maximum value M4 in the electromagnetic wave signal waveform after the power outage is located at a time within 0° and the phase section P4 adjacent to 0° of the commercial power voltage (No in step S15 of Figure 8 and Yes in step S17 of Figure 8), the computer control unit 48 estimates that the cause of the failure is contact with plants (step S18 of Figure 8). Plant contact indicates that the faulty equipment is electrical equipment (which may include electric wires and insulators) that has come into contact with plants, and the reason for the failure is (a ground fault caused by) plant contact, such as at least one of contact with vines and contact with trees. In the case of plant contact, the person responding to the fault should simply inspect the electrical equipment that the plant has come into contact with.

[0047] The computer control unit 48 can estimate causes of faults other than the above four types based on the combination of the zero-phase current signal waveform obtained by a test in which a ground fault is intentionally caused, the electromagnetic wave signal waveform, and the commercial power supply voltage signal waveform. Furthermore, the computer control unit 48 may estimate causes of faults other than the above four types by combining the patterns of the zero-phase current signal waveform and the electromagnetic wave signal waveform obtained by tests such as intentionally causing a ground fault.

[0048] The above-described ground fault cause estimation system 1 is a system that estimates the cause of a ground fault, which is a failure of electrical equipment due to a ground fault. The ground fault cause estimation system 1 includes a computer 6. The computer 6 has a computer communication unit 46, an interface 47, a computer storage unit 44, and a computer control unit 48. The computer communication unit 46 is capable of receiving a zero-phase current signal that is a signal indicating a zero-phase current I0. The interface 47 is capable of receiving an electromagnetic wave signal that is a signal indicating electromagnetic waves generated by partial discharge in electrical equipment. The computer storage unit 44 is capable of storing the zero-phase current signal and the electromagnetic wave signal. The computer control unit 48 estimates the cause of the ground fault based on a zero-phase current signal waveform that is a waveform that indicates the time-dependent change in the zero-phase current signal and an electromagnetic wave signal waveform that is a waveform that indicates the time-dependent change in the electromagnetic wave signal. Therefore, by using two types of information, the zero-phase current signal waveform and the electromagnetic wave signal waveform, for estimation, a ground fault cause estimation system 1 is provided that can estimate the electrical equipment in which a ground fault has occurred. Furthermore, by using these two types of information for estimation, a ground fault cause estimation system 1 is provided that can estimate the reason why a ground fault has occurred. Furthermore, by using these two types of information for estimation, a ground fault cause estimation system 1 is provided that can estimate the cause of a ground fault more quickly and with greater accuracy. In addition, the person responding to the fault can prepare restoration equipment and tools based on the estimated cause, and secure workers according to the cause of the fault to deal with the fault. Therefore, the ground fault cause estimation system 1 makes it easier to respond to the cause of the ground fault and can prevent or quickly resolve power outages.

[0049] The ground fault cause estimation system 1 also includes a zero-phase-sequence current measuring device 4 that acquires a zero-phase-sequence current signal from the zero-phase-sequence current transformer ZCT. The zero-phase-sequence current measuring device 4 transmits the zero-phase-sequence current signal to the computer communication unit 46. Therefore, the zero-phase-sequence current signal is acquired from the zero-phase-sequence current transformer ZCT by a dedicated device. Therefore, the ground fault cause estimation system 1 can estimate the cause of the ground fault more quickly and with higher accuracy. Furthermore, the zero-phase current measuring device 4 includes an AD conversion board 12, a communication unit 29, a CPU 22, a DMAC 26, and a memory 24. The AD conversion board 12 converts the output related to the zero-phase current I0 from the zero-phase current transformer ZCT into a zero-phase current signal. The communication unit 29 transmits the zero-phase current signal to the computer communication unit 46. The CPU 22 can control the communication unit 29. The DMAC 26 stores the zero-phase current signal in the memory 24 without being controlled by the CPU 22. Therefore, by directly storing information in the memory 24 by the DMAC 26, the burden on the CPU 22 is reduced and loss of information related to the zero-phase current I0 is suppressed. Furthermore, variation in the sampling period in AD conversion is suppressed. Therefore, the ground fault cause estimation system 1 can estimate the cause of the ground fault with higher accuracy. Furthermore, the zero-phase-sequence current measuring device 4 includes an AD conversion board 12 that converts the output related to the zero-phase-sequence current I0 from the zero-phase-sequence current transformer ZCT into a zero-phase-sequence current signal. The AD conversion board 12 has a shunt resistor 35. The shunt resistor 35 can be a variable resistor. In this case, adjustments can be made in the zero-phase-sequence current measuring device 4 to acquire a zero-phase-sequence current signal with higher accuracy depending on the conditions of the high-voltage power receiving equipment HVR, including the current transformation ratio of the zero-phase-sequence current transformer ZCT. Therefore, the ground fault cause estimation system 1 can estimate the cause of the ground fault with higher accuracy. In addition, the zero-phase current measuring device 4 includes an AD conversion board 12 that converts the output related to the zero-phase current I0 from the zero-phase current transformer ZCT into a zero-phase current signal. The AD conversion board 12 may include insulating electronic components. In this case, the generation of a common-mode current from the zero-phase current transformer ZCT to the AD conversion board 12 is suppressed. Therefore, a zero-phase current signal with higher accuracy is acquired. Therefore, the ground fault cause estimation system 1 can estimate the cause of the ground fault with higher accuracy.

[0050] Furthermore, the ground fault cause estimation system 1 is equipped with a partial discharge sensor TEVS that acquires an electromagnetic wave signal. The partial discharge sensor TEVS transmits the electromagnetic wave signal to the interface 47. Therefore, the electromagnetic wave signal is acquired by a dedicated device. Therefore, the ground fault cause estimation system 1 can estimate the cause of the ground fault more quickly and with higher accuracy. Furthermore, the partial discharge sensor TEVS has metal plate-shaped electrodes. Therefore, the electromagnetic waves generated by partial discharges in electrical equipment can be measured with sufficient accuracy with a simple configuration. Therefore, the ground fault cause estimation system 1 can more easily estimate the cause of a ground fault with sufficient accuracy. Furthermore, the computer communication unit 46 can receive a commercial power voltage signal, which is a signal indicating the voltage of the commercial power supply. The computer storage unit 44 can store the commercial power voltage signal. The computer control unit 48 compares the electromagnetic wave signal waveform with the commercial power voltage signal waveform, which is a waveform indicating the time-dependent change in the commercial power voltage signal, to determine the phase of the commercial power voltage in the electromagnetic wave signal waveform, and estimates the cause based on the zero-phase current signal waveform and the electromagnetic wave signal waveform whose phase has been determined. Thus, the electromagnetic wave signal waveform can be analyzed more accurately using the phase of the commercial power voltage as an index. Therefore, the ground fault cause estimation system 1 can more accurately estimate the cause of the ground fault. In addition, the ground fault cause estimation system 1 further includes a power supply voltage measurement device 2 that acquires a commercial power supply voltage signal. The power supply voltage measurement device 2 transmits the commercial power supply voltage signal to the computer communication unit 46. Therefore, the commercial power supply voltage signal is acquired by a dedicated device. Therefore, the ground fault cause estimation system 1 can estimate the cause of the ground fault more quickly and with higher accuracy. [Explanation of symbols]

[0051] 1··Earth fault cause estimation system, 2··Power supply voltage measurement device, 4··Zero-phase current measurement device, 6··Computer, 12··AD conversion board (analog-digital conversion section), 22··CPU (control section), 24··Memory (storage section), 26··DMAC (direct memory access controller), 29··Communication section, 35··Shunt resistor, 44··Computer memory section, 46··Computer communication section (computer receiving section), 47··Interface (computer receiving section), 48··Computer control section, HVR··High-voltage power receiving equipment, TEVS··Partial discharge sensor, ZCT··Zero-phase current transformer.

Claims

1. A ground fault cause estimation system that estimates the cause of a ground fault, which is a failure of electrical equipment due to a ground fault, It is equipped with a computer the computer includes a computer receiving unit and a computer control unit; the computer receiving unit is capable of receiving a zero-phase current signal that is a signal indicating a zero-phase current and an electromagnetic wave signal that is a signal indicating an electromagnetic wave generated by partial discharge of the electrical equipment, The computer control unit estimates the cause based on a zero-phase current signal waveform that is a waveform showing a change over time of the zero-phase current signal and an electromagnetic wave signal waveform that is a waveform showing a change over time of the electromagnetic wave signal. A ground fault cause estimation system characterized by:

2. Further, a zero-phase current measuring device is provided which acquires the zero-phase current signal from a zero-phase current transformer, The zero-phase current measuring device transmits the zero-phase current signal to the computer receiving unit.

2. The ground fault cause estimation system according to claim 1.

3. the zero-phase current measuring device includes an analog-to-digital conversion unit, a communication unit, a control unit, a direct memory access controller, and a storage unit; the analog-to-digital converter converts an output relating to the zero-phase current from the zero-phase current transformer into the zero-phase current signal; the communication unit transmits the zero-phase current signal to the computer receiving unit; the control unit is capable of controlling the communication unit, The direct memory access controller stores the zero-phase current signal in the storage unit without being controlled by the control unit.

3. The ground fault cause estimation system according to claim 2.

4. the zero-phase-sequence current measuring device includes an analog-to-digital converter that converts an output related to the zero-phase-sequence current from the zero-phase-sequence current transformer into the zero-phase-sequence current signal; the analog-to-digital conversion unit has a shunt resistor, The shunt resistor is a variable resistor.

3. The ground fault cause estimation system according to claim 2.

5. the zero-phase-sequence current measuring device includes an analog-to-digital converter that converts an output related to the zero-phase-sequence current from the zero-phase-sequence current transformer into the zero-phase-sequence current signal; The analog-to-digital conversion unit has an insulating electronic component.

3. The ground fault cause estimation system according to claim 2.

6. Further, a partial discharge sensor for acquiring the electromagnetic wave signal is provided, The partial discharge sensor transmits the electromagnetic wave signal to the computer receiver.

2. The ground fault cause estimation system according to claim 1.

7. The partial discharge sensor has a metal plate-shaped electrode.

7. The ground fault cause estimation system according to claim 6.

8. the computer receiving unit is capable of receiving a commercial power voltage signal that is a signal indicating the voltage of the commercial power supply; The computer controller comparing the electromagnetic wave signal waveform with a commercial power supply voltage signal waveform that indicates a time-dependent change in the commercial power supply voltage signal, and determining the phase of the commercial power supply voltage in the electromagnetic wave signal waveform; The cause is estimated based on the zero-phase current signal waveform and the electromagnetic wave signal waveform whose phase has been grasped.

2. The ground fault cause estimation system according to claim 1.

9. Further, a power supply voltage measuring device for acquiring the commercial power supply voltage signal is provided, The power supply voltage measuring device transmits the commercial power supply voltage signal to the computer receiving unit.

9. The ground fault cause estimation system according to claim 8.

10. the computer further comprises a computer storage unit; The computer storage unit is capable of storing the zero-phase current signal and the electromagnetic wave signal.

2. The ground fault cause estimation system according to claim 1.

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