Ground fault location estimation device and ground fault location estimation method

Abstract

The power distribution system (1) is provided with power transmission lines (12H, 12F) on which at least one current measuring device (15a to 15e) is arranged, and a power supply device (14) that outputs a current for measuring the zero-phase current. The zero-phase current detection unit (22) detects the zero-phase current from the current measurement results notified by the current measuring devices (15a to 15e). When the earth fault occurrence detection unit (23) detects the occurrence of an earth fault in the power distribution system (1) based on the zero-phase current, it instructs the power supply device (14) to output a current. The earth fault occurrence point estimation unit (25) estimates the occurrence point (16) of the earth fault based on a resonant frequency calculated from a waveform of the zero-phase current detected in response to the current output by the power supply device (14).

Description

[Technical field]

[0001] The present disclosure relates to a ground fault accident Position Estimator and Earth Fault accident It relates to a location estimation method. [Background technology]

[0002] An electric power system is an operational system for supplying electric power to the power receiving equipment of consumers, and is responsible for generating, transforming, transmitting, and distributing electric power. When an accident occurs in an electric power system, the supply of electric power to consumers is stopped. Therefore, it is necessary to quickly identify the cause of the accident, the section where the accident occurred, and the location of the accident, and to carry out restoration work. Conventionally, the location of the accident was generally identified mainly by visual inspection by track maintenance workers, but this method takes a long time to identify the location of the accident in an electric power distribution system with a length of several kilometers to tens of kilometers.

[0003] One type of accident that occurs in a power system is a ground fault. When a ground fault occurs, a zero-phase sequence current and a zero-phase sequence voltage are generated, and therefore, for example, Japanese Patent No. 4550464 (Patent Document 1) describes a method of detecting the occurrence of a ground fault by monitoring the zero-phase sequence current and the zero-phase sequence voltage.

[0004] Furthermore, Patent Document 1 describes a method of estimating a ground fault location from a resonance component included in a zero-phase current waveform. More specifically, the method describes a method of detecting resonance of a zero-phase current detected when a ground fault occurs, calculating the resonance frequency, and comparing the calculated resonance frequency with past data, etc., to estimate the fault location. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4550464 Summary of the Invention [Problem to be solved by the invention]

[0006] The estimation of the earth fault location according to Patent Document 1 is based on the phenomenon in which the resonant frequency of the zero-phase current changes depending on the distance from the substation to the earth fault location. However, since an earth fault may occur due to a lightning strike, contact with a bird or animal, or a tree, it is expected that the earth fault impedance will change in various ways at the moment of occurrence of the earth fault. As a result, when an earth fault occurs, there is a risk that a distorted zero-phase current waveform will be observed, and it is difficult to detect an accurate resonant frequency that reflects the distance from the earth fault location from such a distorted zero-phase current waveform.

[0007] Therefore, in the method described in Patent Document 1, there is a concern that the accuracy of estimating the ground fault location may decrease due to the inability to derive an accurate resonant frequency.

[0008] The present disclosure has been made to solve such problems, and an object of the present disclosure is to improve the accuracy of estimating a ground fault position using a zero-phase current. [Means for solving the problem]

[0009] According to an aspect of the present disclosure, there is provided a ground fault location estimation device for a power distribution system. The power distribution system is provided with a power transmission line on which at least one current meter is arranged, and a power supply device that outputs a current for measuring a zero-phase current to the power transmission line. The ground fault location estimation device includes a current measurement result collection unit, a zero-phase current detection unit, a ground fault occurrence detection unit, and a ground fault occurrence point estimation unit. The current measurement result collection unit collects current measurement results notified from the current meter. The zero-phase current detection unit detects a zero-phase current of the power transmission line from the current measurement results. When the ground fault occurrence detection unit detects an occurrence of a ground fault in the power distribution system based on the detected zero-phase current, it instructs the power supply device to output a current. The ground fault occurrence point estimation unit estimates the occurrence point of the ground fault based on the zero-phase current detected by the current measurement result collection unit and the zero-phase current detection unit in response to the output of the measured current by the power supply device. The ground fault occurrence point estimation unit calculates a resonant frequency from the waveform of the zero-phase current, and estimates the location of the occurrence point based on the calculated resonant frequency.

[0010] According to another aspect of the present disclosure, there is provided a method for estimating a location of a ground fault in a power distribution system. The power distribution system is provided with a power transmission line on which at least one current meter is arranged, and a power supply device that outputs a current for measuring a zero-phase current to the power transmission line. The method for estimating a location of a ground fault includes a step of determining whether or not a ground fault has occurred in the power distribution system based on a zero-phase current of the power transmission line detected from a current measurement result notified from the current meter, a step of instructing the power supply device to output a measurement current when the occurrence of a ground fault is detected, and a step of estimating a location of the ground fault based on the zero-phase current detected from the current measurement result notified from the current meter after the power supply device outputs the measurement current. The estimating step calculates a resonant frequency from a waveform of the zero-phase current, and estimates the location of the occurrence point based on the calculated resonant frequency. Effect of the Invention

[0011] According to the present disclosure, the location of a ground fault can be estimated based on the resonant frequency of the zero-phase current generated by the current from the power supply device after a ground fault occurs, rather than the zero-phase current at the time of the occurrence of a ground fault, which is likely to result in a distorted current waveform, thereby improving the accuracy of estimating the location of the ground fault. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of an entire system of a ground fault position estimating device and a power distribution system according to a first embodiment. [Diagram 2] FIG. 2 is a conceptual diagram for explaining a zero-phase current that occurs when a ground fault occurs in the power distribution system shown in FIG. [Diagram 3] 2 is a block diagram illustrating a configuration of a ground fault occurrence point estimation unit shown in FIG. 1. [Figure 4] FIG. 2 is a block diagram illustrating an example of the configuration of a computer system for realizing a ground fault position estimation device. [Diagram 5] 4 is a flowchart illustrating an example of a control process for estimating a ground fault point by the ground fault position estimating device according to the first embodiment. [Figure 6] FIG. 2 is a conceptual diagram for explaining an outline of correlation data. [Figure 7] FIG. 4 is a conceptual diagram illustrating the function of a ground fault point matching unit. [Figure 8] FIG. 11 is a schematic configuration diagram of an entire system including a ground fault position estimating device and a power distribution system according to a second embodiment. [Figure 9] 9 is a waveform diagram showing a simulation result of the resonance frequency component of the zero-phase current generated when a measurement current is supplied from each power supply device 14 in FIG. 8. FIG. [Figure 10] 1 is a conceptual diagram illustrating the path of a zero-phase current when a measurement current is output from a power supply device located away from a ground fault point. [Figure 11] 1 is a conceptual diagram illustrating a path of a zero-phase current when a measurement current is output from a power supply device in the vicinity of a ground fault point. [Figure 12] 10 is a flowchart illustrating an example of a control process for estimating a ground fault point by the ground fault position estimating device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings are denoted by the same reference characters, and their description will not be repeated in principle.

[0014] Embodiment 1 FIG. 1 is a schematic configuration diagram of a ground fault position estimating device 2A and an entire system of a power distribution system according to the first embodiment.

[0015] As shown in FIG. 1, when a ground fault occurs in a power distribution system 1, a ground fault position estimation device 2A estimates the position (point) at which the ground fault occurs.

[0016] The power distribution system 1 is configured to supply power from a power distribution substation 11 to a plurality of branched feeders 12. The plurality of feeders 12 include a fault feeder 12F in which a ground fault has occurred and a healthy feeder 12H in which no ground fault has occurred. Note that, in this embodiment, a ground fault location estimation is described for the power distribution system 1 in which a plurality of branched feeders 12 are provided, but the ground fault location estimation according to this embodiment can also be applied to the range of a single feeder 12 with no branch.

[0017] Each feeder 12 is assumed to be configured by a general three-phase distribution line, but the number of phases is not limited to this. In Fig. 1, the configuration of a fault feeder 12F is illustrated as an example, but the configuration of each feeder 12 is basically the same. Each of the multiple feeders 12 corresponds to an example of a "power transmission line."

[0018] A plurality of current measuring devices 15 are arranged on the fault feeder 12F, but the arrangement positions and the number (one or more) of the current measuring devices 15 arranged on each feeder 12 are arbitrary. In the example of Fig. 1, in the fault feeder 12F where the current measuring devices 15a to 15e are arranged, a ground fault occurs at a ground fault point 16 located between the current detectors 15c and 15d. In other words, the ground fault point 16 corresponds to the "point where the ground fault occurs."

[0019] Each of the current measuring instruments 15a to 15e measures the current (three-phase current) flowing through the installation location. Each current measuring instrument 15 further has a function of storing measured data and a function of communicating with other devices. Alternatively, the current measuring instrument 15 may be configured as part of the functions of a detector that further has other functions, such as a function of measuring line voltage. The current measurement data Ida to Ide by the current measuring instruments 15a to 15e are input to the ground fault position estimation device 2A.

[0020] A power supply device 14 is further installed in the power distribution system 1 to generate a zero-phase current after the occurrence of a ground fault is detected. The power supply device 14 has a function of outputting a current for measuring the zero-phase current (hereinafter referred to as a "measurement current") in response to an output command from the ground fault position estimation device 2A. The measurement current can be, for example, a pulse current with a period of about 5 [ms] to 10 [ms], but is not limited to this embodiment.

[0021] The power supply device 14 may be arranged for the sole purpose of detecting the ground fault point, but it can also be configured by adding a function to output the above-mentioned measured current in response to an output command from the ground fault location estimation device 2A to a power supply device already installed in the power distribution system 1.

[0022] Moreover, the power supply device 14 may be provided for each feeder 12, or may be provided commonly to a plurality of feeders. In the configuration example of Fig. 1, the measurement current from the power supply device 14 flows through both the faulty feeder 12F and the healthy feeder 12H.

[0023] In addition, a healthy feeder 12H in which no ground fault has occurred has an earth capacitance 17 between itself and the ground GND. The earth capacitance 17 represents the aggregate of earth capacitances distributed in the healthy feeder 12H due to the power distribution line, customer equipment, cables, etc.

[0024] The ground fault position estimation device 2A includes a current measurement result collection unit 21, a zero-phase current detection unit 22, a ground fault occurrence detection unit 23, a data storage unit 24, and a ground fault occurrence point estimation unit 25. The ground fault position estimation device 2A is provided for each predetermined area (detection area) of the power distribution system 1, and uses current measurement data from each current meter 15 arranged in the detection area to identify the fault feeder 12F included in the detection area and estimate the ground fault point 16 in the fault feeder 12F. The ground fault position estimation device 2A illustrated in FIG. 1 is configured to include at least the feeder 12 corresponding to the fault feeder 12F in the detection area.

[0025] The current measurement result collecting unit 21 collects current measurement data Id from each current measuring device 15 arranged on each feeder 12 within the detection area of ​​the ground fault position estimation device 2A. In the configuration example of FIG. 1, the current measurement result collecting unit 21 collects current measurement data Ida to Ide from the current measuring devices 15a to 15e arranged on the fault feeder 12F. The zero-phase current detecting unit 22 calculates the zero-phase current Ipz at each current measuring device 15 from the current measurement value (current measurement data Id) collected by the current measurement result collecting unit 21.

[0026] Fig. 2 is a conceptual diagram for explaining the zero-phase current Ipz that occurs when a ground fault occurs in the power distribution system 1. Fig. 2 shows a flow path of the zero-phase current Ipz in a configuration in which a fault feeder 12F including a ground fault point 16 and two healthy feeders 12H1 and 12H2 are branched off, and a GPT (Grounding Potential Transformer) 18 for detecting the zero-phase voltage Vpaz is disposed near the power distribution substation 11.

[0027] As shown in Fig. 2, each feeder 12 is divided into a plurality of distribution sections by switches 13, and a current meter 15 is disposed in each distribution section. As described in Fig. 1, the ground fault point 16 is located between the current meters 15c and 15d.

[0028] In the fault feeder 12F, the zero-phase current Ipz includes a component flowing through the fault feeder 12F and a component flowing through each of the healthy feeders 12H1 and 12H2. In the fault feeder 12F, the zero-phase current flows into the ground GND at the earth fault point 16, and then flows back to the distribution line (fault feeder 12F) through the earth capacitance 17a or 17b. The earth capacitance 17a corresponds to the sum of the earth capacitance in the section upstream (distribution substation 11 or power supply device 14 side) of the earth fault point 16 in the fault feeder 12F, and the earth capacitance 17a corresponds to the sum of the earth capacitance in the section downstream of the earth fault point 16 in the fault feeder 12F.

[0029] On the other hand, in each of the healthy feeders 12H1 and 12H2, the zero-phase current that flowed into the ground GND at the ground fault point 16 flows through the earth capacitance 17c or 17d and returns to the distribution line (healthy feeders 12H1 and 12H2). The earth capacitance 17c corresponds to the sum of the earth capacitances of the entire healthy feeder 12H1, and the earth capacitance 17d corresponds to the sum of the earth capacitances of the entire healthy feeder 12H2.

[0030] Generally, the impedance of the earth capacitances 17c and 17d of the healthy feeders 12H1 and 12H2 is much smaller than the impedance of the earth fault point 16, so most of the zero-phase current Ipz flows through the fault feeder 12F. For this reason, the magnitude of the zero-phase current measured by the current meter 15 differs between the feeders 12.

[0031] In addition, in the fault feeder 12F, a zero-phase current flows into the ground fault point 16, so the direction of the zero-phase current detected by the current meters 15a to 15c arranged upstream of the ground fault point 16 is different from that detected by the current meters 15d and 15e arranged downstream of the ground fault point 16. On the other hand, in each of the healthy feeders 12H1 and 12H2, the current meters 15 detect the zero-phase current in the same direction.

[0032] Therefore, in each feeder 12, it is possible to determine whether or not a ground fault has occurred based on at least one of the magnitude of the zero-phase current and whether or not the directions of the zero-phase current are aligned. Furthermore, in the fault feeder 12F, it is possible to determine that a ground fault has occurred in a section between two current meters 15 constituting a pair in which the directions of the zero-phase current are opposite, among a plurality of pairs of adjacent two current meters 15. In the example of FIG. 2, it is possible to determine that a ground fault has occurred in a section between current meters 15c and 15d in which the zero-phase current flows in opposite directions. Alternatively, even in a feeder 12 in which only one current meter 15 is arranged, it is possible to determine whether or not a ground fault has occurred based on the magnitude of the zero-phase current.

[0033] It is known that the zero-phase current generates an oscillation component of a resonance frequency determined by the inductance component of the distribution line and the capacitance of the earth capacitance 17a. It is understood that the resonance frequency varies depending on the distance (the distribution line length) from the current supply point (the distribution substation 11 or the power supply device 14) to the earth fault point 16. For this reason, as in Patent Document 1, the position of the earth fault point can be estimated by back-calculating the distance from the resonance frequency of the zero-phase current to the above-mentioned earth fault point 16. It is noted that, when a ground fault occurs, the resonance frequency of the zero-phase current detected at each point (current meter 15) is equal. Therefore, in principle, the resonance frequency can be calculated using the current measurement data Id of any current meter 15. However, as described above, since the amplitude of the zero-phase current differs between the current meter 15, it is preferable to calculate the resonance frequency from the current measurement data Id of an appropriate current meter 15 (for example, a current detector arranged in the fault feeder 12F).

[0034] 1 again, the ground fault occurrence detection unit 23 determines whether or not a ground fault has occurred based on the direction (polarity) of the zero-phase current of each current measuring device 15 calculated by the zero-phase current detection unit 22, and when a ground fault occurs, can identify the fault feeder 12F including the ground fault point 16 from among the multiple feeders 12. Furthermore, based on the polarity of the zero-phase current of each current measuring device 15 in the fault feeder 12F, it can identify a section including the ground fault point 16 (hereinafter also referred to as a "fault section") from each section having two adjacent current measuring devices 15 at both ends.

[0035] When the ground fault occurrence detection unit 23 detects the occurrence of a ground fault, it generates an output command Szc of a measurement current (e.g., a pulse current) for generating a zero-phase current for the power supply device 14. In response to the output command Szc, the power supply device 14 outputs the measurement current, whereby a zero-phase current Ipz is generated in the fault feeder 12F.

[0036] The zero-phase current Ipz generated by the measurement current from the power supply device 14 also contains the above-mentioned resonant frequency components, and can be detected by the zero-phase current detection unit 22 using current measurement data from the current meter 15 (for example, in the fault feeder 12F). The zero-phase current Ipz at this time is input from the zero-phase current detection unit 22 to the ground fault occurrence point estimation unit 25.

[0037] In addition, when the ground fault occurrence detection unit 23 detects the occurrence of a ground fault, it further outputs identification data Dfdx including information for identifying the fault feeder 12F and information for identifying the fault section in the fault feeder 12F. The identification data Dfdx is input from the ground fault occurrence detection unit 23 to the data storage unit 24 and the ground fault occurrence point estimation unit 25.

[0038] The data storage unit 24 stores correlation data between the distance (the length of the distribution line) from a reference point (for example, the arrangement point of the power supply device 14) to the point where a ground fault occurs and the resonance frequency when a ground fault occurs. The correlation data can be created in advance using past accident data in the power distribution system 1 and / or the results of a simulation of a ground fault using a simulator.

[0039] When the data storage unit 24 receives the identification data Dfdx from the ground fault occurrence detection unit 23, that is, when a ground fault is detected, the data storage unit 24 outputs the correlation data to the ground fault occurrence location estimation unit 25.

[0040] The correlation data may be determined in advance for each feeder 12. In this case, from the correlation data of each of the multiple feeders 12, the correlation data corresponding to the fault feeder 12F indicated by the identification data Dfdx is output from the data storage unit 24. In addition, in this embodiment, the correlation data is described as being stored in advance in the data storage unit 24, but it may be input from outside the ground fault position estimation device 2A (such as a server) in response to the output from the ground fault occurrence detection unit 23.

[0041] 3, the ground fault occurrence point estimation unit 25 includes a frequency calculation unit 251 and a ground fault point comparison unit 252. After an output command is issued to the power supply device 14, the frequency calculation unit 251 calculates a resonant frequency from the waveform of the zero-phase current Ipz calculated by the zero-phase current detection unit 22. As described in Patent Document 1, the frequency calculation unit 251 can calculate the resonant frequency by applying a fast Fourier transform (FFT) or the like to the zero-phase current waveform.

[0042] The ground fault point matching unit 252 matches the correlation data with the calculated resonant frequency to obtain an estimated distance from a predetermined reference point (e.g., the power supply device 14) to the point where the ground fault occurred. The estimation result by the ground fault point matching unit 252 is output to the outside from the ground fault position estimation device 2A.

[0043] FIG. 4 is a block diagram illustrating an example of the configuration of a computer system for realizing the ground fault position estimating device 2A.

[0044] As shown in FIG. 4, computer system 40 can have a typical configuration having a display unit 41, an input unit 42, a network interface (I / F) 43, a memory 44, a CPU (Central Processing Unit) 45, a HDD (Hard Disk Drive) 46, and a bus 47.

[0045] The ground fault location estimating device 2A shown in FIG. 4 can be realized by using a computer system 40 as follows.

[0046] Specifically, the function of the current measurement result collecting unit 21 in Fig. 1 can be realized by a network interface (I / F) 43 in Fig. 4 and an analog / digital converter (A / D converter) (not shown) in the input unit 42. Also, the function of the data storing unit 24 can be realized by storing the correlation data using a partial area of ​​the HDD 46 in Fig. 4. Alternatively, when the correlation data is input from outside the ground fault position estimating device 2A, the function can be realized by the network interface 43.

[0047] Furthermore, each of the functions of the zero-phase current detection unit 22, the earth fault occurrence detection unit 23, and the earth fault occurrence point estimation unit 25 can be realized by executing a program stored in the HDD 46 or memory 44 in Figure 4 by the CPU 45 in Figure 4.

[0048] The estimation result obtained by the ground fault occurrence point estimation unit 25 can be displayed to the user using the display unit 41. Alternatively, the estimation result may be transmitted to an external device of the ground fault position estimation device 2A by the network interface 43.

[0049] Alternatively, unlike the example of FIG. 4, at least a part of the ground fault position estimating device 2A can be configured using circuits such as an FPGA (Field Programmable Gate Array) and an ASIC (Application Specific Integrated Circuit).

[0050] FIG. 5 is a flowchart illustrating an example of a control process for estimating a ground fault point by the ground fault position estimating device 2A according to the first embodiment.

[0051] As shown in Fig. 5, in step (hereinafter simply referred to as "S") 100, the ground fault position estimation device 2A determines the presence or absence of a ground fault by the ground fault occurrence detection unit 23 based on the zero-phase current sequentially acquired by the current measurement result collection unit 21 and the zero-phase current detection unit 22. In S110, the process branches depending on the determination result in S100. Specifically, when a ground fault is detected, a YES determination is made in S110, and the process proceeds to S120. On the other hand, when no ground fault is detected (NO determination in S110), the process of S120 is not executed, and the processes of S100 and S110 are repeated.

[0052] In S120, the ground fault position estimation device 2A determines the feeder (fault feeder 12F) and section (fault section) where the ground fault occurred by the ground fault occurrence detection unit 23. As described above, based on the direction (or magnitude and direction) of the zero-phase current Ipz in each current meter 15, the fault feeder 12F and the section where the ground fault occurred (hereinafter also referred to as the "fault section") divided by the two current meter 15 that sandwich the point where the ground fault occurred in the fault feeder 12F are identified. In S120, identification data Dfdx is generated.

[0053] In S130, the ground fault position estimation device 2A generates an output command Szc for the power supply device 14 by the ground fault occurrence detection unit 23. As a result, a measured current (e.g., a pulse current) of the zero-phase current is output from the power supply device 14 to the power distribution system 1 including the ground fault point 16.

[0054] In S140, the ground fault position estimation device 2A calculates the zero-phase current Ipz from the current measurement data Id in each current meter 15 by the current measurement result collector 21 and the zero-phase current detector 22 when the power supply device 14 supplies a measurement current.

[0055] In S150, the ground fault position estimating device 2A causes the ground fault occurrence point estimating unit 25 to acquire the zero-phase current from the zero-phase current detecting unit 22, and in S160, the frequency calculating unit 251 calculates the resonance frequency frs of the zero-phase current.

[0056] In S170, the ground fault position estimation device 2A causes the ground fault occurrence point estimation unit 25 to acquire correlation data including the fault section of the fault feeder 12F from the data storage unit 24.

[0057] FIG. 6 is a conceptual diagram for explaining an outline of correlation data. As shown in Fig. 6, the resonant frequency frs can be calculated from actual data or simulation data when a ground fault occurs at each point of the distribution system 1. By defining a coordinate plane with the horizontal axis representing the resonant frequency frs and the vertical axis representing the distance Dx from a predetermined reference point (e.g., the distribution substation 11 or the power supply device 14) to the point where the ground fault occurs, it is possible to plot characteristic points defined by a combination of the resonant frequency frs and the distance Dx from the reference point corresponding to each point. The reference point corresponds to a source of current that generates a zero-phase current, and is the distribution substation 11 in the case where actual data is used, but can be either the distribution substation 11 or the power supply device 14 depending on the setting of the simulation conditions in the case where simulation data is used.

[0058] From these plotted points, a characteristic line 50 can be obtained that indicates the relationship between the resonance frequency frs and the distance Dx from the reference point. In the example of Fig. 6, the characteristic line 50 is obtained by linear approximation, but the characteristic line 50 may be obtained by approximation using a curve or an arbitrary function.

[0059] The correlation data is a data group for expressing the characteristic line 50, and can be, for example, data indicating the coordinates of (frs, Dx) at multiple points on the characteristic line 50. In this case, the distance Dx from the reference point for any resonant frequency frs of the zero-phase current within the expected range can be obtained by interpolation or extrapolation for the multiple points indicated by the correlation data.

[0060] Referring to FIG. 5 again, in S180, the ground fault location estimation device 2A estimates the ground fault point from the correlation data acquired in S170 and the resonance frequency of the zero-phase current calculated in S160 by the ground fault point collation unit 252.

[0061] FIG. 7 is a conceptual diagram for explaining the function of the ground fault point collation unit 252. As shown in FIG. 7, the ground fault point collation unit 252 can obtain the estimated distance Des (Dx = Des) from the reference point corresponding to the resonance frequency frs = fes calculated in S160 on the characteristic line 50 according to the correlation data acquired in S170. This estimated distance Des corresponds to the length of the distribution line from the reference point (for example, the current supply point by the power supply device 14) in the correlation data of FIG. 6.

[0062] The ground fault point collation unit 252 can obtain the estimated position of the ground fault point on the distribution system 1 as an estimation result by using the topology information of the distribution system 1 created in advance and the calculated estimated distance. For example, in the power transmission path passing through the accident section from the power supply device 14, which is an example of the reference point indicated by the above topology information, the point where the distance from the power supply device 14 (the length of the distribution line) = D1 can be obtained as the estimated position of the ground fault point.

[0063] Referring to FIG. 5 again, in S190, the ground fault location estimation device 2A outputs the data DRfp indicating the estimation result obtained by the ground fault point collation unit 252 to the outside. For example, when the ground fault location estimation device 2A is arranged at the manned command post of the monitoring system, the estimated position of the ground fault point can be displayed using the display unit 41 (FIG. 4) such as a display. Alternatively, when the ground fault location estimation device 2A is arranged at an unmanned substation or the like, the estimation result obtained by the ground fault point collation unit 252 can be output via the network interface 43 so as to be transmitted to an external device such as the device of the above command post. That is, the ground fault location estimation device 2A can be arranged at an arbitrary location.

[0064] As described above, the ground fault position estimation device according to the first embodiment can estimate the position of the ground fault point by using the resonant frequency calculated from the waveform of the zero-phase current generated by supplying the current of the power supply device 14 to the power distribution system 1 including the ground fault point 16 after the occurrence of a ground fault, rather than the waveform of the zero-phase current obtained when the ground fault occurs. In particular, the accuracy of estimating the position of the ground fault point can be improved by calculating an accurate resonant frequency that reflects the distance (the length of the distribution line) from the power supply device 14 that supplies the measurement current to the ground fault point 16.

[0065] Embodiment 2 8 is a schematic configuration diagram of an entire system of a ground fault location estimation device and a power distribution system according to embodiment 2. In embodiment 2, the description will focus on the parts different from embodiment 1, and therefore the description of matters common to embodiment 1 will not be repeated.

[0066] 8, a power distribution system 1 to which a ground fault position estimation device 2B according to the second embodiment is applied is provided with a plurality of power supply devices 14. For example, in the example of FIG. 8, a plurality of power supply devices 14A and 14B are provided in the power distribution system 1.

[0067] The ground fault position estimation device 2B differs from the ground fault position estimation device 2B of embodiment 1 in that, when the occurrence of a ground fault is detected, it has a function of selecting one power supply device from the multiple power supply devices 14 that outputs a current (measurement current) for measuring the zero-phase current.

[0068] In the example of FIG. 8, compared to the ground fault position estimation device 2A, the ground fault occurrence detection unit 23 of the ground fault position estimation device 2B generates an output command Szca for the power supply device 14A and an output command Szcb for the power supply device 14B separately. The output commands Szca and Szcb are selectively generated. When the output command Szca is generated, the power supply device 14A outputs a measurement current, whereas when the output command Szcb is generated, the power supply device 14B outputs a measurement current. The measurement current is, for example, a pulse current, as in the first embodiment.

[0069] Furthermore, with regard to the correlation data stored in the data storage unit 24, the correlation data for the power supply device 14 described in the first embodiment is prepared in correspondence with each of the multiple power supply devices 14. That is, in the example of Fig. 8, individual correlation data is prepared for each of the power supply devices 14A and 14B. Note that, also in the second embodiment, the correlation data may be input from outside the ground fault position estimation device 2B (such as a server) in response to an output from the ground fault occurrence detection unit 23.

[0070] Similarly to the ground fault position estimation device 2A, the ground fault position estimation device 2B can be configured by the computer system 40 illustrated in FIG. 4, or at least some of the functions can be configured using circuits such as FPGA and ASIC.

[0071] Next, the selection of multiple power supply devices will be described with reference to Figures 9 to 11. Here, a case is assumed in which, in power distribution system 1, power supply device 14B is located near ground fault point 16, and power supply device 14A is located some distance away from ground fault point 16, as shown in Figure 8.

[0072] Fig. 9 is a waveform diagram that shows a schematic simulation result of the resonant frequency component of the zero-phase current generated when a measurement current is supplied from each power supply device 14 in Fig. 8. Fig. 9 shows a waveform diagram of the resonant current component in which the fundamental wave component has been removed and only the vibration component has been extracted from the simulation result of the zero-phase current generated when a predetermined current pulse (measurement current) is output from each of the power supply devices 14A and 14B under the condition that the ground fault point 16 in Fig. 8 is grounded in a circuit model simulating the power distribution system 1.

[0073] 9, when a resonant current waveform 101 obtained when a current pulse is output from the power supply device 14A is compared with a resonant current waveform 102 obtained when a current pulse is output from the power supply device 14B, the two have the same frequency but a difference in amplitude, and the amplitude of the resonant current waveform 102 (power supply device 14B) is smaller than that of the resonant current waveform 101 (power supply device 14B). Therefore, it can be seen that calculating the resonant frequency using the resonant current waveform 101 is easier than calculating the resonant frequency using the resonant current waveform 102, and the calculation accuracy of the resonant frequency is also improved.

[0074] FIG. 10 shows a conceptual diagram illustrating the path of a zero-phase current when a current pulse (measurement current) is output from power supply device 14A.

[0075] As shown in FIG. 10, the power supply device 14A is located upstream (on the distribution substation 11 side) of the branch point of the fault feeder 12F and the healthy feeders 12H1 and 12H2, and is located relatively far from the ground fault point 16.

[0076] The zero-phase current Ipz generated by the current pulse (measurement current) output from the power supply unit 14A results in a current (Ipz1) flowing through the faulty feeder 12F and currents (Ipz2, Ipz3) flowing through the healthy feeders 12H1 and 12H2 being generated in parallel, and the frequency (resonant frequency) of the vibration component changes depending on the position of the ground fault point 16.

[0077] Therefore, the zero-phase current can be considered to flow through a parallel circuit of a first impedance corresponding to each of the healthy feeders 12H1 and 12H2 from the power supply device 14A and a second impedance from the power supply device 14A to the ground fault point 16 of the fault feeder 12F.

[0078] The oscillation of the zero-phase current occurs due to the exchange of energy between the first impedance and the second impedance. Therefore, in the example of Fig. 10, it can be understood that the path length through which the zero-phase current flows is relatively long, and the inductance component of the distribution line is also large.

[0079] In contrast to this, FIG. 11 shows a conceptual diagram illustrating the path of the zero-phase current when a current pulse (measurement current) is output from power supply device 14B.

[0080] As shown in FIG. 11, the power supply device 14B is disposed near the ground fault point 16 in the fault feeder 12F.

[0081] Almost all of the zero-phase current Ipz generated by the current pulse (measurement current) output from the power supply device 14B flows into the ground fault point 16, and the inductance component of the power distribution line in the path of the zero-phase current becomes very small. In this case, energy exchange between the impedances connected in parallel as shown in Fig. 10 is unlikely to occur. As a result, it can be seen that resonance is less likely to occur in the case of Fig. 11 than in the case of Fig. 10.

[0082] As a result, as shown in FIG. 9, a simulation result is obtained in which the resonant current waveform 102 (power supply device 14A) has a larger amplitude than the resonant current waveform 101 (power supply device 14B).

[0083] It is known that the resonance sharpness (Q value) in an LC circuit depends on the inductance component L and the capacitance component C, and is proportional to √(L / C). Since the resonance sharpness increases when the inductance component of the power distribution line in the path of the zero-phase current is large, it can be understood that the calculation of the resonance frequency becomes easier and more accurate.

[0084] Therefore, when multiple power supply devices 14 are arranged, it is understood that one power supply device (hereinafter also referred to as a "selected power supply device") that outputs a measurement current should be selected based on the positional relationship between each power supply device 14 and the ground fault point 16, so as to avoid using a power supply device 14 that is too close to the ground fault point 16. In the example of Figures 8 to 11, it is understood that when a ground fault occurs in the section between current measuring instruments 15d and 15e, the measurement current should be output from power supply device 14A located farther away, not from nearby power supply device 14B.

[0085] Referring to FIG. 8 again, as described in the first embodiment, the ground fault accident occurrence detection unit 23 can identify the accident feeder 12F and the accident section within the accident feeder 12F based on the direction of the zero-phase current detected by each ammeter 15 of each feeder 12. Therefore, based on the configuration of the power distribution system 1, for each section of each feeder 12, a selection power supply device can be predetermined from a plurality of power supply devices 14. For example, power selection list data indicating the selection power supply device for each section of each feeder 12 can be stored in advance in the data storage unit 24.

[0086] Then, the ground fault accident occurrence detection unit 23 can read out selection data Dsl indicating the selection power supply device corresponding to the accident section indicated by the specific data Dfdx by referring to the power selection list data stored in the data storage unit 24. The ground fault accident occurrence detection unit 23 can output an output command Szc to one of the plurality of power supply devices 14 based on the selection data Dsl read from the data storage unit 24. In the example of FIG. 8, when selection data Dsl designating the power supply device 14A is returned from the data storage unit 24 for the accident section (including the ground fault accident point 16) between the ammeters 15d and 15e of the accident feeder 12F, the ground fault accident occurrence detection unit 23 will generate an output command Szca for the power supply device 14A.

[0087] FIG. 12 is a flowchart for explaining an example of the control process for estimating the ground fault accident point by the ground fault accident position estimation device according to the second embodiment.

[0088] As shown in FIG. 12, the ground fault accident position estimation device 2B performs, by S100 to S120 similar to those in FIG. 5, the detection determination of the ground fault accident based on the zero-phase current and the determination of identifying the accident feeder 12F and the accident section at the time of the ground fault accident occurrence by the ground fault accident occurrence detection unit 23.

[0089] When the ground fault position estimation device 2B identifies the fault section in the fault feeder 12F in S120, the ground fault occurrence detection unit 23 notifies the data storage unit 24 of the determination result identifying the fault section in S210. Furthermore, the ground fault position estimation device 2B acquires the selection result of the power supply device 14 corresponding to the fault section by the data storage unit 24 referring to the above-mentioned power supply selection list data in S220. The selection result is notified to the ground fault occurrence detection unit 23 from the data storage unit 24.

[0090] In S130, the ground fault position estimation device 2B generates a measurement current output command for the power supply device 14 selected in S220. When one power supply device 14 that received the output command generated in S130 outputs the measurement current, the processes of S130 to S190 similar to those in FIG. 5 are executed.

[0091] In the second embodiment, as in the first embodiment, a resonant frequency is calculated based on a zero-phase current waveform generated by a measurement current output from one power supply device (selected power supply device) (S140 to S160). Furthermore, in S170, correlation data (FIG. 5) corresponding to the power supply device 14 selected in S220 is extracted, and the distance (length of the power distribution line) from a predetermined reference point (for example, the power supply device 14 that generated the measurement current) is estimated from the resonant frequency, thereby making it possible to estimate the ground fault point as in the first embodiment (S180).

[0092] As described above, the ground fault location estimation device according to the second embodiment can select a power supply device that outputs a current for measuring the zero-phase current in consideration of the positional relationship with the fault section (the length of the power distribution line) when a ground fault occurs. In this way, in addition to the effects described in the first embodiment, the accuracy of detection of the resonant frequency can be improved, thereby improving the accuracy of estimation of the ground fault point.

[0093] In the second embodiment, the number and locations of the multiple power supply devices 14 in the power distribution system 1 are arbitrary, but for each point in the power distribution system 1, taking into account the distance between each power supply device 14 (the length of the distribution line), it is possible to predetermine one power supply device to be used for estimating the ground fault point in this embodiment for each point (e.g., each section of each feeder 12).

[0094] 8 and 12 have described an example in which power source selection list data stored in advance in the data storage unit 24 is used, but the power source selection list data may be input from outside the ground fault position estimation device 2B (such as a server) in response to the output from the ground fault occurrence detection unit 23. Alternatively, information specifying the power source device 14 to be selected corresponding to the detected fault section may be input to the ground fault position estimation device 2B from outside the ground fault position estimation device 2B without using a power source selection list.

[0095] In addition, since the actual configuration of the power distribution system 1 is a complex combination of branches of the feeders 12 illustrated in Figures 1 and 8, it is difficult to strictly formulate the relationship between the resonant frequency and the length of the power distribution line. However, as described in Figure 6, by using past accident record data and / or simulation data to prepare in advance characteristic curve 50 for each power supply path (feeder 12) in the power distribution system 1, it is possible to apply the estimation of the ground fault point described in this embodiment.

[0096] Note that the control processing for estimating the ground fault point shown in Figures 5 and 12 is merely an example, and it is possible to add, change, delete, or otherwise modify the processing as desired within the scope that achieves the same effect.

[0097] As described above, the ground fault location estimation device according to the present embodiment can be provided for each predetermined area (detection area) of the power distribution system 1, and in some cases, it is also possible to arrange the area within the range without feeder branching (for example, for each feeder after branching in FIGS. 1 and 8) as the detection area. In the estimation of the ground fault location within a single feeder 12 (transmission line) without branching, after detecting the ground fault based on the zero-phase current, the specific processing (S120) of the accident feeder 12F described in Embodiments 1 and 2 is unnecessary, and it is possible to instruct the output of the measured current to a specific power supply device 14 in response to the detection of the ground fault.

[0098] Also, in the estimation of the ground fault location within a single feeder 12 (transmission line), it is possible to estimate the ground fault point based on the estimated distance (the total length of the distribution line) from a predetermined reference point based on the resonance frequency without requiring specific information about the accident feeder 12F. On the other hand, in the power distribution system 1 provided with a plurality of branched feeders 12, since there may be a point where the distance from the reference point is the same for each feeder 12, it is necessary to estimate the ground fault location by combining the specific information of the accident feeder 12F.

[0099] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0100] 1 distribution system, 2A, 2B fault location estimation device, 11 distribution substation, 12 feeder, 12F fault feeder, 12H1, 12H, 12H2 healthy feeder, 13 switch, 14, 14A, 14B power supply device, 15, 15a, 15c, 15d, 15e current meter, 16 earth fault point, 17 earth capacitance, 17a, 17c, 17d earth capacitance, 21 current measurement result collection unit, 22 zero-phase current detection unit, 23 fault occurrence detection unit, 24 data storage unit, 25 fault occurrence location estimation unit, 40 computer system, 50 characteristic line, 101, 102 resonant current waveform, 251 frequency calculation unit, 252 earth fault point comparison unit, DRfp data (estimation result), Dfdx specific data, Dsl selection data, Dx Distance, GND ground, Id, Ida~Ide current measurement data, Ipz zero-phase current, Szc, Szca, Szcb output command, frs resonance frequency.

Claims

1. A ground fault location estimation device for a power distribution system, comprising a power transmission line on which a plurality of current measuring instruments for measuring the three-phase current flowing through the installation location are arranged, and a power supply device that outputs a current for measuring the zero-sequence current to the power transmission line, A current measurement result collection unit that collects current measurement results notified from the aforementioned multiple current measuring instruments, A zero-sequence current detection unit that detects the zero-sequence current of the power transmission line from the current measurement results, A ground fault detection unit, which detects the occurrence of a ground fault in the power distribution system based on the detected zero-sequence current, instructs the power supply unit to output the current, The system includes a ground fault location estimation unit that estimates the location of the ground fault based on the zero-sequence current detected by the current measurement result collection unit and the zero-sequence current detection unit in response to the output of the current from the power supply unit, The ground fault location estimation unit calculates a resonant frequency from the waveform of the zero-sequence current and estimates the location of the fault based on the calculated resonant frequency, and is a ground fault location estimation device.

2. The ground fault location estimation device according to claim 1, wherein the ground fault detection unit estimates the location of the fault location according to the estimated distance from a predetermined reference point based on the resonant frequency to the fault location.

3. The aforementioned power distribution system is provided with a plurality of branched transmission lines. The power supply unit is provided in each of the transmission lines, or in common for the plurality of transmission lines. When the occurrence of the ground fault is detected, the ground fault detection unit further determines which of the plurality of transmission lines the fault location is located in, based on the zero-sequence current detected in each of the current measuring instruments. The ground fault location estimation device according to claim 1, wherein the ground fault location estimation unit estimates the location of the fault location according to information indicating the faulty transmission line among the plurality of transmission lines that includes the fault location, and the estimated distance from the power supply unit to the fault location based on the resonant frequency.

4. The aforementioned power distribution system has multiple power supply units located in different locations. The ground fault location estimation device according to claim 1, wherein when the ground fault occurrence detection unit detects the occurrence of the ground fault, it further determines which of the plurality of sections, which are divided by the arrangement positions of the plurality of current measuring instruments, the occurrence point is included in, based on the polarity of each zero-sequence current detected in accordance with each of the current measuring instruments, and instructs one of the plurality of power supply devices selected according to the location of the fault section in which the occurrence point is included among the plurality of power transmission lines to output the current.

5. The aforementioned power distribution system is provided with a plurality of branched transmission lines. Multiple current measuring instruments are installed in each of the aforementioned power transmission lines. When a ground fault is detected, the ground fault detection unit further determines which of the plurality of transmission lines the fault location is located in, based on the polarity of each zero-sequence current detected in each of the current measuring instruments. The ground fault location estimation device according to claim 4, wherein the ground fault location estimation unit estimates the location of the fault according to information indicating the faulty transmission line among the plurality of transmission lines that includes the fault location, and the estimated distance from the power supply unit to the fault location based on the resonant frequency.

6. The power supply device is installed in a distribution substation of the distribution system, and is a ground fault location estimation device according to any one of claims 1 to 5.

7. The ground fault location estimation device according to any one of claims 1 to 5, wherein the power supply device is configured to output the current to each phase of the three-phase distribution line of the power transmission line.

8. A method for estimating the location of a ground fault in a power distribution system, comprising a power transmission line on which a plurality of current measuring instruments for measuring the three-phase current flowing through the installation location are arranged, and a power supply device that outputs a current for measuring the zero-sequence current to the power transmission line, The steps include determining whether or not a ground fault has occurred in the distribution system based on the zero-sequence current of the transmission line detected from the current measurement results notified by the plurality of current measuring instruments, When the occurrence of the aforementioned ground fault is detected, the power supply device is instructed to output the aforementioned current; The system includes the step of estimating the location of the ground fault based on the zero-sequence current detected from the current measurement result notified by the current measuring instrument after the output of the current by the power supply device, The aforementioned estimation step is, A method for estimating the location of a ground fault, comprising calculating a resonant frequency from the waveform of the zero-sequence current and estimating the location of the fault based on the calculated resonant frequency.

9. The ground fault location estimation method according to claim 8, wherein the estimation step involves estimating the location of the occurrence point according to the estimated distance from a predetermined reference point based on the resonant frequency to the occurrence point.

10. The aforementioned power distribution system is provided with a plurality of branched transmission lines. The power supply unit is provided in each of the transmission lines, or in common for the plurality of transmission lines. The above determination step, when the occurrence of the ground fault is detected, further determines which of the plurality of transmission lines the fault location is located in, based on the zero-sequence current detected in each of the current measuring instruments. The ground fault location estimation method according to claim 8, wherein the estimation step involves estimating the location of the fault point according to information indicating the fault transmission line among the plurality of transmission lines that includes the fault point, and the estimated distance from the power supply unit to the fault point based on the resonant frequency.

11. The aforementioned power distribution system has multiple power supply units installed in different locations. The above determination step, when the occurrence of the ground fault is detected, further determines which of the multiple sections, separated by the arrangement positions of the multiple current measuring instruments, the location of the fault is included in, based on the polarity of each zero-sequence current detected in relation to each of the multiple current measuring instruments. The ground fault location estimation method according to claim 8, wherein the instruction step involves instructing one of the plurality of power supply devices selected according to the location of the fault section including the point of occurrence among the plurality of power transmission lines to output the current.

12. The aforementioned power distribution system is provided with a plurality of branched transmission lines. Multiple current measuring instruments are installed in each of the aforementioned power transmission lines. The above determination step, when a ground fault is detected, further determines which of the plurality of transmission lines the fault location is located in, based on the polarity of each zero-sequence current detected in each of the current measuring instruments. The ground fault location estimation method according to claim 11, wherein the estimation step involves estimating the location of the fault point according to information indicating the fault transmission line including the fault point among the plurality of transmission lines, and the estimated distance from the power supply unit to the fault point based on the resonant frequency.

13. The ground fault location estimation method according to any one of claims 8 to 12, wherein the instruction step is to instruct the power supply device to output the current to each phase of the three-phase distribution line of the power transmission line.

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