Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/08—Locating faults in cables, transmission lines, or networks
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
  • G01R31/52—Testing for short-circuits, leakage current or ground faults
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
  • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
  • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
  • Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
  • Y04S10/52—Outage or fault management, e.g. fault detection or location

Definitions

• This disclosure relates to a ground fault location estimation device and a ground fault location estimation method.
• Power grids are operational systems that supply power to consumers' power receiving equipment, and are responsible for generating, transforming, transmitting, and distributing electricity. If an accident occurs in a power grid, the supply of power to consumers will be cut off. 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 then carry out restoration work. Traditionally, the location of an accident has mainly been identified visually by track maintenance workers, but this method takes a long time to identify the location of the accident in power distribution systems with lengths ranging from several kilometers to tens of kilometers.
• a ground fault One type of accident that can occur in a power system is a ground fault.
• a ground fault occurs, a zero-phase sequence current and a zero-phase sequence voltage are generated. Therefore, as described in, for example, Japanese Patent No. 4550464 (Patent Document 1), the occurrence of a ground fault can be detected by monitoring the zero-phase sequence current and voltage.
• Patent Document 1 describes a method for estimating the location of a ground fault from the resonant component contained in the zero-phase current waveform. More specifically, the method describes a method for detecting the resonance of the zero-phase current detected when a ground fault occurs, calculating the resonant frequency, and comparing the calculated resonant frequency with past data, etc., to estimate the location of the fault.
• the estimation of the ground fault location in 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 ground fault location.
• ground faults can occur due to lightning strikes, contact with birds and animals, or trees, it is expected that the ground fault impedance will change in various ways at the moment a ground fault occurs.
• a ground 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 ground fault location from such a distorted zero-phase current waveform.
• This disclosure has been made to solve these problems, and its purpose is to improve the accuracy of estimating ground fault locations using zero-phase current.
• a ground fault location estimation device for a power distribution system.
• the power distribution system is provided with a transmission line on which at least one current meter is disposed, and a power supply device that outputs a current for measuring zero-phase current to the 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 the zero-phase current of the transmission line from the current measurement results.
• the ground fault occurrence detection unit When the ground fault occurrence detection unit detects the 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 location estimation unit calculates the resonant frequency from the waveform of the zero-phase current and estimates the location of the occurrence point based on the calculated resonant frequency.
• a method for estimating the location of a ground fault in a power distribution system is provided with a transmission line on which at least one current meter is installed, and a power supply device that outputs a current for measuring the zero-phase current to the transmission line.
• the method for estimating the location of a ground fault includes the steps of: determining whether a ground fault has occurred in the power distribution system based on the zero-phase current of the transmission line detected from the current measurement results notified by the current meter; instructing the power supply device to output a measured current when a ground fault has occurred; and estimating the location of the ground fault based on the zero-phase current detected from the current measurement results notified by the current meter after the power supply device outputs the measured current.
• the estimating step calculates a resonant frequency from the waveform of the zero-phase current, and estimates the location of the occurrence based on the calculated resonant frequency.
• 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 ground fault, which is likely to result in a distorted current waveform. This improves the accuracy of estimating the location of the ground fault.
• FIG. 1 is a schematic configuration diagram of an entire system including a ground fault location estimation device and a power distribution system according to a first embodiment
• 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. 1
• FIG. 2 is a block diagram illustrating the configuration of a ground fault occurrence point estimation unit shown in FIG. 1
• FIG. 1 is a block diagram illustrating an example of the configuration of a computer system for realizing a ground fault location estimation device. 4 is a flowchart illustrating an example of a control process for estimating a ground fault point by the ground fault position estimation device according to the first embodiment.
• FIG. 1 is a conceptual diagram illustrating an outline of correlation data.
• FIG. 1 is a conceptual diagram illustrating an outline of correlation data.
• FIG. 4 is a conceptual diagram illustrating the function of a ground fault point matching unit.
• 10 is a schematic configuration diagram of an entire system including a ground fault location estimation device and a power distribution system according to a second embodiment.
• FIG. 9 is a waveform diagram schematically 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. 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.
• 1 is a conceptual diagram illustrating the path of a zero-phase current when a measurement current is output from a power supply device near a ground fault point.
• 10 is a flowchart illustrating an example of a control process for estimating a ground fault point by a ground fault position estimation device according to a second embodiment.
• FIG. 1 is a schematic configuration diagram of a ground fault location estimation device 2A and an entire system of a power distribution system according to the first embodiment.
• the ground fault location estimation device 2A estimates the location (occurrence point) of the ground fault.
• the power distribution system 1 is configured so that power is supplied from a distribution substation 11 to multiple branched feeders 12.
• the multiple 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 while this embodiment describes ground fault location estimation for a power distribution system 1 having multiple branched feeders 12, the ground fault location estimation according to this embodiment can also be applied to the range of a single feeder 12 with no branches.
• Each feeder 12 is assumed to be configured as a typical three-phase distribution line, but the number of phases is not limited to this. While Figure 1 illustrates the configuration of a fault feeder 12F, the configuration of each feeder 12 is basically the same. Each of the multiple feeders 12 corresponds to an example of a "transmission line.”
• ground fault point 16 corresponds to the "point where the ground fault occurred.”
• Each of the current measuring devices 15a to 15e measures the current (three-phase current) flowing at the installation location.
• Each current measuring device 15 also has the function of storing measured data and the function of communicating with other devices.
• the current measuring device 15 may be configured as part of a detector that also has other functions, such as measuring line voltage.
• the current measurement data Ida to Ide from the current measuring devices 15a to 15e is input to the ground fault location estimation device 2A.
• the power distribution system 1 is further equipped with a power supply device 14 for generating a zero-phase current after detecting the occurrence of a ground fault.
• the power supply device 14 has the function of outputting a current for measuring the zero-phase current (hereinafter referred to as the "measurement current") in response to an output command from the ground fault location estimation device 2A.
• the measurement current can be, for example, a pulse current with a period of approximately 5 ms to 10 ms, but is not limited to this form.
• the power supply device 14 may be arranged exclusively for detecting ground fault points, but it can also be configured by adding a function to an existing power supply device in the power distribution system 1 to output the above-mentioned measured current in response to an output command from the ground fault location estimation device 2A.
• the power supply device 14 may be provided for each feeder 12, or may be provided in common for multiple feeders. In the configuration example shown in Figure 1, the measurement current from the power supply device 14 flows through both the faulted feeder 12F and the healthy feeder 12H.
• a healthy feeder 12H in which no ground fault has occurred has a capacitance to ground 17 between it and ground GND.
• the capacitance to ground 17 represents the aggregate of the capacitance to ground distributed within the healthy feeder 12H due to the distribution lines, customer equipment, cables, etc.
• the ground fault location estimation device 2A comprises 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 location 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 located within the detection area to identify the fault feeder 12F contained within the detection area and estimate the ground fault point 16 within the fault feeder 12F.
• the ground fault location estimation device 2A illustrated in Figure 1 is configured to include at least the feeder 12 corresponding to the fault feeder 12F in its detection area.
• the current measurement result collection unit 21 collects current measurement data Id from each current meter 15 installed on each feeder 12 within the detection area of the ground fault location estimation device 2A.
• the current measurement result collection unit 21 collects current measurement data Ida to Ide from current meter 15a to 15e installed on the fault feeder 12F.
• the zero-phase current detection unit 22 calculates the zero-phase current Ipz at each current meter 15 from the current measurement value (current measurement data Id) collected by the current measurement result collection unit 21.
• Figure 2 is a conceptual diagram illustrating the zero-phase current Ipz that occurs when a ground fault occurs in the distribution system 1.
• Figure 2 shows the flow path of the zero-phase current Ipz in a configuration in which a fault feeder 12F, which includes a ground fault point 16, branches off from two healthy feeders 12H1 and 12H2, and a GPT (Grounding Potential Transformer) 18 for detecting the zero-phase voltage Vpaz is located near the distribution substation 11.
• GPT Global System for Transformer
• each feeder 12 is divided into multiple distribution sections by switches 13, and a current meter 15 is installed in each distribution section.
• the ground fault point 16 is located between current meters 15c and 15d.
• the zero-phase current Ipz includes a component that flows through the fault feeder 12F and a component that flows through each of the healthy feeders 12H1 and 12H2.
• the zero-phase current flows into ground GND at the earth fault point 16, then passes through earth capacitance 17a or 17b and flows back to the distribution line (fault feeder 12F).
• Earth capacitance 17a corresponds to the sum of the earth capacitances in the section upstream of the earth fault point 16 in the fault feeder 12F (towards the distribution substation 11 or power supply 14), and earth capacitance 17a corresponds to the sum of the earth capacitances in the section downstream of the earth fault point 16 in the fault feeder 12F.
• earth capacitance 17c corresponds to the sum of the earth capacitances of all healthy feeders 12H1
• earth capacitance 17d corresponds to the sum of the earth capacitances of all healthy feeders 12H2.
• 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 faulty feeder 12F. For this reason, the magnitude of the zero-phase current measured by the current meter 15 differs between the feeders 12.
• the current measuring instruments 15 detect zero-phase current in the same direction.
• each feeder 12 it is possible to determine whether a ground fault has occurred based on at least one of the magnitude of the zero-phase current and whether the direction of the zero-phase current is consistent. Furthermore, in the fault feeder 12F, it is possible to determine that a ground fault has occurred in the section between two current meters 15 that form a pair of adjacent pairs of current meters 15, where the zero-phase current flows in opposite directions. In the example of Figure 2, it is possible to determine that a ground fault has occurred in the section between current meters 15c and 15d, where the zero-phase current flows in opposite directions. Alternatively, even in a feeder 12 where only one current meter 15 is installed, it is possible to determine whether a ground fault has occurred based on the magnitude of the zero-phase current.
• the zero-phase current generates an oscillation component at a resonant frequency determined by the inductance component of the distribution line and the capacitance of the earth capacitance 17a. It is understood that this resonant frequency varies depending on the distance (distribution line length) from the current supply point (distribution substation 11 or power supply unit 14) to the earth fault point 16. Therefore, as in Patent Document 1, the location of the earth fault point can be estimated by back-calculating the distance to the above-mentioned earth fault point 16 from the resonant frequency of the zero-phase current. When a ground fault occurs, the resonant frequency of the zero-phase current detected at each point (current meter 15) will be the same.
• the resonant frequency can be calculated using the current measurement data Id from any current meter 15.
• the appropriate current meter 15 for example, the current detector installed on the fault feeder 12F.
• the ground fault occurrence detection unit 23 determines whether 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, it can identify the fault feeder 12F containing 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 within the fault feeder 12F, it can identify the section containing the ground fault point 16 (hereinafter also referred to as the "fault section”) from each section having two adjacent current measuring devices 15 at both ends.
• the fault section section containing the ground fault point 16
• the ground fault occurrence detection unit 23 When the ground fault occurrence detection unit 23 detects the occurrence of a ground fault, it generates an output command Szc for the power supply device 14 to output a measurement current (e.g., a pulse current) to generate a zero-phase current. In response to the output command Szc, the power supply device 14 outputs the measurement current, thereby generating a zero-phase current Ipz in the fault feeder 12F.
• a measurement current e.g., a pulse current
• 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 (e.g., 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 location estimation unit 25.
• the ground fault accident detection unit 23 detects the occurrence of a ground fault accident, it further outputs identification data Dfdx including information identifying the fault feeder 12F and information identifying the fault section within the fault feeder 12F.
• the identification data Dfdx is input from the ground fault accident detection unit 23 to the data storage unit 24 and the ground fault accident occurrence location estimation unit 25.
• the data storage unit 24 stores correlation data between the distance (length of the distribution line) from a reference point (e.g., the location of the power supply unit 14) to the point where a ground fault occurs and the resonant frequency when a ground fault occurs.
• This correlation data can be created in advance using past accident data in the distribution system 1 and/or the results of a ground fault simulation using a simulator.
• the data storage unit 24 When the specific data Dfdx is input from the ground fault occurrence detection unit 23, i.e., when a ground fault is detected, the data storage unit 24 outputs the correlation data to the ground fault occurrence location estimation unit 25.
• the correlation data may be determined in advance for each feeder 12.
• the correlation data corresponding to the fault feeder 12F indicated by the specific data Dfdx is output from the data storage unit 24.
• the correlation data is described as being stored in advance in the data storage unit 24, but it may also be input from outside the ground fault location estimation device 2A (such as a server) in response to the output from the ground fault occurrence detection unit 23.
• the ground fault occurrence location estimation unit 25 is composed of a frequency calculation unit 251 and a ground fault point matching unit 252.
• the frequency calculation unit 251 calculates the resonant frequency from the waveform of the zero-phase current Ipz calculated by the zero-phase current detection unit 22.
• 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.
• FFT fast Fourier transform
• the ground fault point matching unit 252 matches the correlation data with the calculated resonant frequency to determine the estimated distance from a predetermined reference point (e.g., power supply unit 14) to the point where the ground fault occurred.
• the estimation result by the ground fault point matching unit 252 is output externally from the ground fault location estimation device 2A.
• Figure 4 is a block diagram illustrating an example configuration of a computer system for implementing the ground fault location estimation device 2A.
• the computer system 40 can have a typical configuration, including a display unit 41, an input unit 42, a network interface (I/F) 43, memory 44, a CPU (Central Processing Unit) 45, an HDD (Hard Disk Drive) 46, and a bus 47.
• I/F network interface
• CPU Central Processing Unit
• HDD Hard Disk Drive
• the ground fault location estimation device 2A shown in Figure 4 can be implemented as follows using a computer system 40.
• the function of the current measurement result collection unit 21 in FIG. 1 can be realized by the network interface (I/F) 43 in FIG. 4 and an analog-to-digital converter (A/D converter) (not shown) in the input unit 42.
• the function of the data storage unit 24 can be realized by storing correlation data using a partial area of the HDD 46 in FIG. 4.
• this function can be realized by the network interface 43.
• the functions of the zero-phase current detection unit 22, the ground fault occurrence detection unit 23, and the ground fault occurrence location estimation unit 25 can be realized by the CPU 45 in FIG. 4 executing programs stored in the HDD 46 or memory 44 in FIG. 4.
• the estimation results obtained by the ground fault occurrence location estimation unit 25 can be displayed to the user using the display unit 41.
• the estimation results may be transmitted to an external device of the ground fault location estimation device 2A via the network interface 43.
• At least a portion of the ground fault location estimation device 2A can be configured using circuits such as an FPGA (Field Programmable Gate Array) and an ASIC (Application Specific Integrated Circuit).
• FPGA Field Programmable Gate Array
• ASIC Application Specific Integrated Circuit
• Figure 5 is a flowchart illustrating an example of control processing for estimating a ground fault point by the ground fault position estimation device 2A according to embodiment 1.
• step (hereinafter simply referred to as "S") 100 the ground fault location estimation device 2A determines whether or not a ground fault has occurred using 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.
• S110 processing branches depending on the determination result in S100. Specifically, if a ground fault is detected, a YES determination is made in S110 and processing proceeds to S120. On the other hand, if no ground fault is detected (a NO determination is made in S110), processing in S120 is not executed, and processing in S100 and S110 is repeated.
• the ground fault location estimation device 2A uses the ground fault occurrence detection unit 23 to determine the feeder (fault feeder 12F) and section (fault section) where the ground fault occurred. As described above, based on the direction (or magnitude and direction) of the zero-phase current Ipz at each current meter 15, the fault feeder 12F and the section where the ground fault occurred (hereinafter also referred to as the "fault section") separated by the two current meters 15 that sandwich the point where the ground fault occurred within the fault feeder 12F are identified. In S120, identification data Dfdx is generated.
• the ground fault location estimation device 2A generates an output command Szc to the power supply device 14 using the ground fault occurrence detection unit 23.
• the power supply device 14 outputs a measured zero-phase current (e.g., a pulse current) to the power distribution system 1 including the ground fault point 16.
• the ground fault location estimation device 2A calculates the zero-phase current Ipz from the current measurement data Id in each current meter 15 using the current measurement result collection unit 21 and the zero-phase current detection unit 22.
• the ground fault location estimation device 2A acquires the zero-phase current from the zero-phase current detection unit 22 using the ground fault occurrence location estimation unit 25, and in S160, the frequency calculation unit 251 calculates the resonant frequency frs of the zero-phase current.
• the ground fault location estimation device 2A uses the ground fault occurrence location estimation unit 25 to acquire correlation data including the fault section of the fault feeder 12F from the data storage unit 24.
• FIG. 6 is a conceptual diagram for explaining an outline of correlation data.
• the resonant frequency frs can be calculated from actual data or simulation data when a ground fault occurs at each point in the distribution system 1.
• a predetermined reference point e.g., the distribution substation 11 or the power supply device 14
• characteristic points defined by the combination of the resonant frequency frs and the distance Dx from the reference point can be plotted for each point.
• the reference point corresponds to the source of the current that generates the zero-phase current, and in the case where actual data is used, it is the distribution substation 11.
• simulation data it can be either the distribution substation 11 or the power supply device 14 depending on the simulation conditions.
• a characteristic line 50 can be obtained that represents the relationship between the resonant frequency frs and the distance Dx from the reference point.
• the characteristic line 50 is obtained by linear approximation, but the characteristic line 50 may also be obtained by approximation using a curve or an arbitrary function.
• the correlation data is a group of data used to represent the characteristic line 50, and can be, for example, data indicating the coordinates (frs, Dx) at multiple points on the characteristic line 50.
• the distance Dx from the reference point can be determined for any resonant frequency frs of the zero-phase current within the expected range.
• the ground fault location estimation device 2A uses the ground fault point matching unit 252 to estimate the ground fault point from the correlation data acquired in S170 and the resonant frequency of the zero-phase current calculated in S160.
• FIG. 7 is a conceptual diagram illustrating the function of the ground fault point matching unit 252.
• This estimated distance Des corresponds to the length of the power distribution line from the reference point (e.g., the point where current is supplied by the power supply device 14) in the correlation data of FIG.
• the ground fault point matching unit 252 can use the topology information of the power distribution system 1 created in advance and the calculated estimated distance to determine the estimated location of the ground fault point on the power distribution system 1 as an estimation result. For example, on the power transmission route that passes through the fault section from the power supply unit 14, which is an example of a reference point indicated by the topology information, the point at distance D1 from the power supply unit 14 (length of the distribution line) can be determined as the estimated location of the ground fault point.
• the ground fault position estimation device 2A outputs data DRfp indicating the estimation result obtained by the ground fault point matching unit 252 to the outside at S190.
• the ground fault position estimation device 2A is located in a manned control center of a monitoring system
• the estimated position of the ground fault point can be displayed using a display unit 41 (FIG. 4), such as a display.
• the estimation result obtained by the ground fault point matching unit 252 can be output via the network interface 43 so as to be transmitted from the ground fault position estimation device 2A to external equipment, such as equipment in the control center.
• the ground fault position estimation device 2A can be located anywhere.
• the ground fault location estimation device of embodiment 1 can estimate the location of the ground fault point using a resonant frequency calculated from the waveform of the zero-phase current generated by supplying current from the power supply device 14 to the power distribution system 1 including the ground fault point 16 after the ground fault occurs, rather than the waveform of the zero-phase current obtained when the ground fault occurs.
• a resonant frequency calculated from the waveform of the zero-phase current generated by supplying current from the power supply device 14 to the power distribution system 1 including the ground fault point 16 after the ground fault occurs, rather than the waveform of the zero-phase current obtained when the ground fault occurs.
• the accuracy of estimating the location of the ground fault point can be improved.
• 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.
• the explanation will focus on the parts that are different from embodiment 1, and therefore, the explanation of matters that are common to embodiment 1 will not be repeated.
• a power distribution system 1 to which a ground fault location estimation device 2B according to embodiment 2 is applied is provided with a plurality of power supply devices 14.
• a plurality of power supply devices 14A and 14B are provided in the power distribution system 1.
• the ground fault location estimation device 2B differs from the ground fault location estimation device 2B according to embodiment 1 in that, when a ground fault is detected, it has the function of selecting one power supply device from multiple power supply devices 14 that outputs a current (measurement current) for measuring the zero-phase current.
• the ground fault occurrence detection unit 23 of the ground fault location estimation device 2B separately generates an output command Szca for the power supply device 14A and an output command Szcb for the power supply device 14B.
• the output commands Szca and Szcb are generated selectively.
• the power supply device 14A outputs a measurement current
• the power supply device 14B outputs a measurement current.
• the measurement current is, for example, a pulse current.
• correlation data for each of the multiple power supply units 14 described in embodiment 1 is prepared. That is, in the example of FIG. 8, individual correlation data is prepared for each of the power supply units 14A and 14B. Note that, in embodiment 2 as well, correlation data may be input from outside the ground fault location estimation device 2B (such as a server) in response to output from the ground fault occurrence detection unit 23.
• the ground fault location estimation device 2B can be configured using the computer system 40 illustrated in FIG. 4, or at least some of its functions can be configured using circuits such as FPGAs and ASICs.
• Figure 9 is a waveform diagram that schematically shows the simulation results of the resonant frequency component of the zero-phase current that occurs when a measurement current is supplied from each power supply unit 14 in Figure 8.
• Figure 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 results of the zero-phase current that occurs when a predetermined current pulse (measurement current) is output from each of power supply units 14A and 14B under the condition that the earth fault point 16 in Figure 8 is grounded in a circuit model that simulates the power distribution system 1.
• Figure 10 shows a conceptual diagram explaining the path of the zero-phase current when a current pulse (measurement current) is output from power supply unit 14A.
• the power supply unit 14A is located upstream (towards the distribution substation 11) 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.
• the zero-phase current Ipz generated by the current pulse (measurement current) output from power supply unit 14A results in the current (Ipz1) flowing through faulty feeder 12F and the currents (Ipz2, Ipz3) flowing through healthy feeders 12H1 and 12H2 occurring in parallel, and the frequency of the vibration component (resonant frequency) changes depending on the position of the earth fault point 16.
• the zero-phase current can be considered to flow through a parallel circuit consisting of a first impedance from power supply 14A corresponding to each of healthy feeders 12H1 and 12H2, and a second impedance from power supply 14A to the ground fault point 16 of fault feeder 12F.
• Figure 11 shows a conceptual diagram explaining the path of the zero-phase current when a current pulse (measurement current) is output from power supply unit 14B.
• power supply unit 14B is located near the ground fault point 16 on fault feeder 12F.
• the simulation results show that the resonant current waveform 102 (power supply device 14A) has a larger amplitude than the resonant current waveform 101 (power supply device 14B).
• the resonance sharpness (Q value) of an LC circuit depends on the inductance component L and 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 zero-phase current path is large, it can be seen that this makes it easier and more accurate to calculate the resonance frequency.
• the selected power supply device one power supply device that outputs the 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.
• the measurement current should be output from the distant power supply device 14A, rather than the nearby power supply device 14B.
• the ground fault occurrence detection unit 23, as described in embodiment 1, can identify the fault feeder 12F and the fault section within the fault feeder 12F based on the direction of the zero-phase current detected by each current meter 15 of each feeder 12. Therefore, based on the configuration of the power distribution system 1, a selected power supply device can be predetermined from multiple power supplies 14 for each section of each feeder 12. For example, power supply selection list data indicating the selected power supply device for each section of each feeder 12 can be stored in advance in the data storage unit 24.
• the ground fault accident detection unit 23 can read out selection data Dsl indicating the selected power supply corresponding to the fault section indicated by the specific data Dfdx.
• the ground fault accident detection unit 23 can output an output command Szc to one of the multiple power supply units 14 based on the selection data Dsl read out from the data storage unit 24.
• the selection data Dsl specifying power supply unit 14A is returned from the data storage unit 24 for the fault section (including the ground fault point 16) between current meters 15d and 15e of the fault feeder 12F, causing the ground fault accident detection unit 23 to generate an output command Szca for power supply unit 14A.
• Figure 12 is a flowchart illustrating an example of control processing for estimating a ground fault point using a ground fault location estimation device according to embodiment 2.
• the ground fault location estimation device 2B performs steps S100 to S120, similar to those in FIG. 5, using the ground fault occurrence detection unit 23 to detect and determine a ground fault based on the zero-phase current, and to determine the fault feeder 12F and the fault section when a ground fault occurs.
• the ground fault occurrence detection unit 23 When the ground fault location estimation device 2B identifies the fault section within 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, in S220, the data storage unit 24 references the above-mentioned power source selection list data to obtain the selection result of the power supply device 14 corresponding to the fault section. The selection result is notified from the data storage unit 24 to the ground fault occurrence detection unit 23.
• the ground fault location estimation device 2B generates a measurement current output command for the power supply device 14 selected in S220.
• the resonant frequency is calculated based on the zero-phase current waveform generated by the measured current output from one power supply (selected power supply) (S140-S160). Furthermore, in S170, correlation data ( Figure 5) corresponding to the power supply 14 selected in S220 is extracted, and the distance (length of the distribution line) from a predetermined reference point (e.g., the power supply 14 that generated the measured current) can be estimated from the resonant frequency, thereby estimating the ground fault point, as in the first embodiment (S180).
• a predetermined reference point e.g., the power supply 14 that generated the measured current
• the ground fault location estimation device when a ground fault occurs, it is possible to select a power supply device that outputs a current for measuring the zero-phase current, taking into account its positional relationship with the fault section (the length of the distribution line). This not only achieves the effects explained in embodiment 1, but also improves the accuracy of detecting the resonant frequency, thereby improving the accuracy of estimating the ground fault point.
• the number and locations of the multiple power supply devices 14 within the distribution system 1 are arbitrary, but for each point within the 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).
• Figures 8 and 12 illustrate an example in which power source selection list data stored in advance in the data storage unit 24 is used
• the power source selection list data may be input from outside the ground fault location estimation device 2B (such as a server) in response to output from the ground fault occurrence detection unit 23.
• information specifying the power source device 14 to be selected corresponding to the detected fault section may be input to the ground fault location estimation device 2B from outside the ground fault location estimation device 2B.
• control processes for estimating the ground fault point shown in Figures 5 and 12 are merely examples, and it is possible to add, change, delete, or otherwise modify the processes as desired within the scope of achieving the same effect.
• the ground fault location estimation device can be installed in each predetermined area (detection area) of the power distribution system 1, and in some cases, it can also be placed as a detection area within an area where there are no feeder branches (for example, each feeder after branching in Figures 1 and 8).
• the process of identifying the fault feeder 12F (S120) described in embodiments 1 and 2 is not required, and a specific power supply device 14 can be instructed to output a measurement current in response to the detection of a ground fault.
• Distribution system 2A, 2B. Fault location estimation device, 11. Distribution substation, 12. Feeder, 12F. Fault feeder, 12H1, 12H, 12H2. Healthy feeders, 13. Switch, 14, 14A, 14B. Power supply unit, 15, 15a, 15c, 15d, 15e. Current measuring device, 16. Earth fault point, 17. Capacitance to earth, 17a, 17c, 17d. Capacitance to earth, 21. Current measurement result collection unit, 22. Zero-phase current detection unit, 23.
• Fault occurrence detection unit unit 24 data storage unit, 25 fault location estimation unit, 40 computer system, 50 characteristic line, 101, 102 resonant current waveform, 251 frequency calculation unit, 252 earth fault point matching unit, DRfp data (estimation result), Dfdx specific data, Dsl selection data, Dx distance, GND ground, Id, Ida to Ide current measurement data, Ipz zero-phase current, Szc, Szca, Szcb output command, frs resonant frequency.

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• 2024
  • 2024-04-26 WO PCT/JP2024/016554 patent/WO2025225014A1/ja active Pending
  • 2024-04-26 JP JP2024565988A patent/JP7682407B1/ja active Active

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