JP5026906B2 - Ground fault occurrence bank identification method and ground fault occurrence bank identification device - Google Patents

Description

  The present invention generates a ground fault in a distribution system such as a multiple grounding type low-voltage AC distribution line in which B-type ground wires of a plurality of banks (post transformers) supplying power to a low-voltage consumer are connected in parallel by a common ground wire. The present invention relates to a bank specifying method and a specifying device.

If the transformer class B ground wire of each bank is individually grounded, if a ground fault occurs in any of the low-voltage consumers such as houses, factories, and offices that are powered from the bank's low-voltage AC distribution line The ground fault current flows only in the B-type ground line of the bank that supplies electric power to the low-voltage consumer that generates the ground fault. In the bank where there is a ground fault in the low voltage customer in multiple banks, since the ground fault current does not flow in another bank without the ground fault occurrence, it is performed only for the bank where the ground fault occurs, and the earth leakage breaker Check the operation of a low-voltage customer with a low-voltage customer who does not have an earth leakage breaker and measure the magnitude of the ground fault current with a lead-in wire. Is identified. Furthermore, the location of the ground fault is determined by measuring the magnitude of the ground fault current on the low-voltage AC distribution line of the low-voltage customer who has been able to identify the occurrence of the ground fault (see, for example, Patent Document 1).
JP 2004-101352 A

  Class B grounding work on the neutral line or one terminal of the transformer secondary side of the bank is multiplexed by connecting the B grounding lines of each bank in parallel in addition to single grounding for each bank. There is multiple grounding. Depending on the conditions of the land where Class B grounding work is performed, it may be economically difficult to maintain the grounding resistance at a specified value with single grounding. In such a case, the B type grounding wires of a plurality of banks are connected in parallel with a common grounding wire to lower the combined grounding resistance value and keep it at a specified value.

  In a multiple grounding (overhead joint ground type) low-voltage AC distribution line with multiple banks grounded, a ground fault occurs in a low-voltage customer supplied with power from any one bank, and a ground fault current flows. In such a case, a ground fault current corresponding to the ground resistance value flows not only in the B type ground line of the ground fault occurrence bank but also in the B type ground lines of all other banks connected through the common ground line. For this reason, it is not possible to specify a bank that supplies power to low-voltage consumers in which a ground fault has occurred, and it is not possible to use the service lines or load lines of all low-voltage consumers that are supplied with power from all banks that are jointly grounded with Class B grounding. It was necessary to measure the ground fault current, and the specific range was so wide that it was difficult to identify and work on the ground fault occurrence bank.

  Further, by separating the B-type grounding of each of the plurality of banks and returning to the single grounding, it is possible to identify the bank where the ground fault occurs. In this case, not only the trouble of disconnecting the B type grounding in a plurality of banks and the trouble of returning to the original multiple grounding is required, but also in the intermittent grounding in which the ground fault is generated intermittently, Until the next ground fault occurs, there is a problem that causes the state that the class B ground resistance value is less than the specified value, and the reliability is lacking.

  An object of the present invention is to provide a ground fault occurrence bank identification method and identification apparatus that can easily identify a ground fault occurrence bank with a small number of work steps.

  The method of the present invention is a method for identifying a bank corresponding to any ground fault occurrence low voltage AC distribution line in a distribution system in which a plurality of banks of low voltage AC distribution lines are connected in parallel, and between a plurality of low voltage AC distribution lines The ground fault current is detected at each parallel connection location where no load current flows, and the phase of each detected ground fault current is measured based on the common reference time signal, and the ground current at the adjacent parallel connection location is measured. The bank corresponding to the ground fault occurrence low voltage AC distribution line is specified based on the determination of whether the phase of the fault current is the same phase or the opposite phase.

  Here, when a ground fault current flows in one of the low-voltage AC distribution lines of the plurality of banks, the ground fault current flows to one of the low-voltage AC distribution lines in which the ground fault occurs. It is a distribution system consisting of a plurality of low-voltage AC distribution lines connected in parallel so as to flow. A single-phase AC type or a three-phase AC type low-voltage distribution line can be applied to the plurality of low-voltage AC distribution lines connected in parallel. The parallel connection location between adjacent low-voltage AC distribution lines is a location where load current does not flow. When a ground fault current flows due to the occurrence of a ground fault in any one of a plurality of parallel connection locations, this ground fault current is grounded. It also flows through other low-voltage AC distribution lines where no ground fault occurs. A ground fault current flows in each of the plurality of parallel connection locations in a magnitude and direction determined by the positional relationship with the ground fault occurrence bank. The direction of the ground fault current at each parallel connection location is detected by measuring the phase of each ground fault current detected at each parallel connection location based on a common reference time signal. When the phase of the ground fault current in each adjacent parallel connection location is the same phase, it can be determined that the ground fault current flowing in each parallel connection location is in the same direction. In addition, when the phase of the ground fault current at each adjacent parallel connection location is in reverse phase, it can be determined that the ground fault current flowing through each parallel connection location is in the reverse direction of 180 ° and is sandwiched between the adjacent parallel connection locations. It can be determined that the bank is a ground fault occurrence bank. The direction of the ground fault current at each parallel connection point can also be detected from the phase difference between the ground fault current and the line voltage of the low-voltage AC distribution line, or the phase difference between the ground fault current and the ground voltage. By measuring on the basis of the reference time signal at the time of detection, the ground fault occurrence bank can be specified only by the operation of detecting the ground fault current, and the workability of specifying the ground fault occurrence bank is improved.

  In the present invention, the reference time signal can be generated based on a pulse signal synchronized with the commercial power source of the low-voltage AC distribution line. In addition, the reference time signal can be generated based on a pulse signal from a pulse oscillation circuit that oscillates a pulse signal at a frequency obtained by dividing the commercial frequency of the low-voltage AC distribution line by an integer. Furthermore, the reference time signal can be generated based on the GPS signal of the global positioning system.

  The reference time signal generated based on the pulse signal synchronized with the commercial power source of the above-described low-voltage AC distribution line is used even if a slight frequency fluctuation occurs in the commercial power source of the low-voltage AC distribution line. Since the frequency of the ground fault current fluctuates, the ground fault current phase can always be measured with high accuracy. When the reference time signal is generated based on a pulse signal from a pulse oscillation circuit that oscillates a pulse signal having a frequency of 1 / n obtained by dividing the commercial frequency of the low-voltage AC distribution line by an integer n, the integer n is 1, Either one of 2 and 4 is desirable for measuring the ground fault current phase with high accuracy. In addition, the reference time signal generated in synchronization with the GPS signal of the global positioning system (GPS) can be used as an absolute reference time signal without error. In this case, the ground fault current phase measurement can always be performed with high accuracy. it can.

  The low-voltage AC distribution line is a multi-grounding type low-voltage AC distribution line in which multiple B class ground wires are connected in parallel with a common ground line. It is possible to identify a ground fault occurrence bank by detecting a ground fault current at each parallel connection point.

  As the low-voltage AC distribution line in this case, a single-phase AC type or three-phase AC type low-voltage distribution line connected to the high-voltage distribution line by a bank that is a pole transformer can be applied. A plurality of banks in this low-voltage AC distribution line are pole transformer systems that supply power to low-voltage consumers such as houses and factories, and transformer B class ground wires of each bank are connected by a common common ground wire and multiplexed. Grounded. When a ground fault occurs due to leakage in one bank, a ground fault current flows through the B-type ground lines and common ground lines of all banks including the bank where the ground fault occurs. The ground fault current in each bank is an alternating current, and the current direction is a repetition of the direction flowing into the bank where the ground fault occurs and the direction flowing out from the bank where the ground fault occurs. By measuring the ground fault current direction in each bank based on the reference time signal, the ground fault occurrence bank can be specified. In this case, it is desirable to detect the direction of the ground fault current in all of the plurality of banks. However, depending on the position of the ground fault occurrence bank, if the direction of the ground fault current is detected by a small number of banks, the bank in which the ground fault occurs can be specified. Such a ground fault generation bank can be specified while the multiple grounding type low-voltage AC distribution line is kept in multiple grounding. Therefore, it is possible to specify the ground fault occurrence bank with labor and time that are almost the same as in the case of the type B single grounding.

  In addition, a current transformer that detects a ground fault current is installed at each parallel connection point that is a joint ground line between multiple banks of the multiple ground type low-voltage AC distribution line, and the ground fault current is simultaneously detected at the multiple parallel connection points. And the phase (direction) of the detected ground fault current can be measured based on the reference time signal. Furthermore, it is possible to sequentially detect the ground fault current at a plurality of parallel connection locations and measure the phase (direction) based on the reference time signal. In this latter case, a single current transformer that detects the ground fault current detects the ground fault current at each parallel connection location in sequence, stores phase (direction) data for each ground fault current detection, and if necessary Can be displayed on the display and sent to a remote location.

  The device of the present invention is a device for identifying a bank corresponding to any ground fault occurrence low-voltage AC distribution line in a distribution system in which a plurality of banks of low-voltage AC distribution lines are connected in parallel. A ground fault current detector that detects a ground fault current flowing through the parallel connection location at each connection location, and a common reference time signal that serves as a reference for measuring the phase of each ground fault current detected at the parallel connection location The reference time signal generation unit for generating the current and the phase of the ground fault current at the adjacent parallel connection location are determined to be in phase or opposite to each other, and the bank sandwiched between the adjacent parallel connection locations determined to be in reverse phase A ground fault bank determination unit that determines a fault occurrence bank.

  Here, the reference time signal generation unit can have a structure including a superposed current transformer that superimposes a high-frequency pulse current synchronized with the commercial power source of the low-voltage AC distribution line on the parallel connection portion.

  The ground-fault current detector in the device of the present invention is a current transformer that sequentially moves to a plurality of parallel connection locations between the low-voltage AC distribution lines, or a permanent transformer one at each of the plurality of parallel connection locations. It can be set as the structure which has several current transformers installed in a line. In addition, the reference time signal generation unit includes a zero cross detection circuit that detects, for example, a zero cross of the commercial power supply voltage of the low-voltage AC distribution line, a pulse generation circuit that generates a pulse synchronized with the rising point of the zero cross of the commercial voltage, and a generated pulse. It can comprise with the superimposition current transformer made to superimpose on either of the several parallel connection places of the low voltage | pressure AC distribution line. Furthermore, the reference time signal generation unit can be applied with a GPS reception function or with a dedicated pulse oscillation circuit. In addition, the ground fault bank determination unit stores and displays whether the phase of the ground fault current at each of the plurality of parallel connection locations and the ground fault current phase of the adjacent two parallel connection locations are in phase or reverse phase. In the case of a phase, one having a function of voice display indicating that it is a ground fault occurrence bank can be applied. Furthermore, those having a function of transmitting data to be stored and displayed to a remote place such as an electric power company can be applied.

  According to the present invention, the phase and direction of the ground fault current detected at each parallel connection point between the low-voltage AC distribution lines are measured based on the reference time signal common to each parallel connection point, and at each parallel connection point, Since it is determined whether the phase of the ground fault current is in phase or opposite to each other, it is easy to operate without measuring the line voltage or ground voltage of the low voltage AC distribution line, and always generates a ground fault with high accuracy. The bank can be specified. In particular, even if a ground fault occurs in one of the multiple banks of the multi-grounding type low-voltage AC distribution line, and a ground fault current flows through the multiple banks, the bank in which the ground fault occurs can be identified with multiple grounds. Therefore, the bank ground fault countermeasure of the multi-grounding type low-voltage AC distribution line can be always accurately performed with good workability.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 shows an application to a single-phase three-wire multiple grounding type low-voltage AC distribution line 1 in which B-type grounding wires 4 of a plurality of banks B are connected in parallel by a common grounding wire 5. Class B ground wire 4 of each bank B connected to the high-voltage AC distribution line is on the low-voltage line neutral line when there is a low-voltage line on the transformer secondary side of the low-voltage column, and directly on the column when there is no low-voltage line Connected to transformer neutral wire. The number of banks B shown in FIG. 1 is 5, which are referred to as banks B1, B2, B3, B4, and B5 from the left in FIG. The ground resistance value in each of the banks B1 to B5 is a combined ground resistance value when the ground resistances of the five banks B1 to B5 are connected in parallel. When the load current does not flow in the common ground line 5 and a ground fault occurs in the low-voltage consumer of any bank, the size of each of the five banks B1 to B5 is determined by the positional relationship with the ground fault generating bank. A ground fault current flows.

  The ground fault current due to the occurrence of a ground fault is detected during periodic grounding resistance measurement of each bank B1 to B5, or due to a leakage request from a house, factory, office, etc. Done. The ground fault occurrence bank identification device 10 shown in FIG. 1 includes a ground fault current detection unit 20, a reference time signal generation unit 30, and a ground fault bank determination unit 40. Prior to the description of the ground fault occurrence bank specifying apparatus 10, how the ground fault current flows in each of the banks B1 to B5 when the ground fault bank is generated will be described.

  FIG. 1 shows a case where a ground fault occurs due to a ground fault in a low-voltage consumer supplied from the third bank B3 from the left in FIG. 1 among the five banks B1 to B5, and a ground fault current Ig flows. This ground fault current Ig is a commercial alternating current, and flows out from the ground fault generation bank to the ground. The ground fault current Ig3 returns from the ground to the ground fault generation bank B3 through the B-type ground line 4 of the ground fault generation bank B3. The ground fault current Ig passes through the B-type ground lines 4 of the other banks B1, B2, B4, and B5 where no ground fault has occurred, and the currents Ig1, Ig2, Ig4, and Ig5 return from the ground. The currents Ig1, Ig2, Ig4, and Ig5 return to the bank B3 where the ground fault has occurred through the common ground line 5.

  There are five connection points 11 between the common grounding wire 5 and the B-type grounding wires 4 of the banks B1 to B5, and both side lines of the connection points 11 of the three banks B2, B3, B4 are connected in parallel at the points 12a, 12b, 12c and 12d. Ground fault currents Ia, Ib, Ic, and Id described later flow through the parallel connection portions 12a to 12d of the four lines. The local fault currents Ia to Id are determined by the positional relationship between the bank in which the ground fault has occurred and the bank in which no ground fault has occurred in the direction and magnitude of the current.

  The ground fault current Ig flowing out from the ground fault occurrence bank B3 to the ground returns from the ground through all the B-type ground lines 4 of the five banks B1 to B5 connected by the common ground line 5. Since the directions of the currents Ig1 to Ig5 are the same, even if the ground fault currents Ig1 to Ig5 flowing through the B-type ground line 4 are detected, the ground fault occurrence bank is not known.

  In FIG. 1, the ground fault current Ia flowing in the parallel connection location 12a between the first bank B1 and the second bank B2 from the left end flows in the direction from the left to the right in FIG. . In FIG. 1, the ground fault current Ib flowing in the parallel connection location 12b between the second bank B2 and the third bank B3 from the left end flows in the direction from the left to the right in FIG. . This ground fault current Ib is a current obtained by joining the ground fault currents Ia from the parallel connection points 12a and is larger than the ground fault current Ia. Further, since the ground fault current Ic flowing in the parallel connection location 12c between the third bank B3 and the fourth bank B4 from the left end in FIG. 1 returns to the bank B3 where the ground fault occurs, the direction from the right to the left in FIG. Flowing into. Further, since the ground fault current Id flowing in the parallel connection point 12d between the fourth bank B4 and the fifth bank B5 from the left end in FIG. 1 returns to the bank B3 where the ground fault occurs, the direction from the right to the left in FIG. To join the ground fault current Ic. That is, the ground fault current directions of the parallel connection locations 12b and 12c sandwiching the bank B3 where the ground fault occurs are 180 ° reverse and the phase is 180 ° reverse. From this, it can be determined that the bank into which the ground fault current just flows from the adjacent bank is the ground fault occurrence bank. In the bank where no ground fault has occurred, the direction of the ground fault current flowing through the common ground line with the adjacent bank is the same, and the phase is the same.

  The ground fault occurrence bank specifying device 10 in FIG. 1 detects a ground fault current at an arbitrary adjacent parallel connection point 12 and determines whether each of the flowing directions is the same or opposite depending on whether the phase is the same phase or opposite phase. In this way, the ground fault occurrence bank is specified. The ground fault current detection unit 20 detects the ground fault current flowing through the parallel connection points 12a to 12d. The reference time signal generator 30 generates a common reference time signal CP, which is a reference for measuring the phase of each ground fault current detected at the parallel connection points 12a to 12d, and the ground fault bank determination unit 40 It is determined whether the phase of the ground fault current at the adjacent parallel connection points 12a to 12d is the same phase or opposite to each other, and the bank sandwiched between the two adjacent parallel connection points determined to be opposite in phase is determined as the ground fault occurrence bank. To do.

  The ground fault current detection unit 20 includes a current transformer CT that detects a ground fault current flowing in the parallel connection locations 12a to 12d. The number of current transformers CT to be used is arbitrary as single or plural, and in the case of a single current transformer CT, the current transformer CT is sequentially installed and used at each of the parallel connection points 12a to 12d in the four-line section. In FIG. 1, four current transformers CT1 to CT4 are shown for explaining the method of the present invention, but the number is arbitrary. Hereinafter, the four current transformers CT1 to CT4 are referred to as detection CT1 to CT4 as necessary.

  The reference time signal generation unit 30 shown in FIG. 1 generates a reference time signal CP based on a pulse signal synchronized with the commercial power supply of the bank B which is a low-voltage AC distribution line. This reference time signal generation unit 30 is synchronized with the commercial power supply of the low-voltage AC distribution line of any one bank B, for example, a zero-cross detection circuit 31 that detects a zero-cross of a commercial power supply voltage of a sine wave, and a zero-cross of the commercial voltage A pulse generation circuit 32 that generates a pulse synchronized with the rising point of the current and a superposition current transformer 33 that superimposes the generated pulse on any one of the common ground lines 5. Hereinafter, the superimposed current transformer 33 is referred to as a superimposed CT as necessary.

  FIG. 2 shows a pulse waveform superimposed by the superimposed CT and a ground fault current waveform detected by the detection CT1 to CT4. The superimposed CT detects a commercial low-voltage line voltage, generates a pulse synchronized with the rising point of the zero cross as a reference time signal CP, and superimposes it on the common ground line 5. On the other hand, the ground fault current Ia is detected by the detection CT1 of the common ground line 5, for example, installed at the parallel connection location 12a. Since the detected current is a sine wave having a commercial frequency and a superimposed pulse is input as noise, the ground fault current Ia is detected by removing the noise component with a band-pass filter or the like. The ground fault bank determination unit 40 measures the rise time of the ground fault current Ia with reference to the reference time signal CP, and calculates the current phase θ ° with respect to the reference.

  In addition, the ground fault current Ib is detected by the detection CT2 installed in the parallel connection location 12b, the rise time of the ground fault current Ib with reference to the reference time signal CP is measured by the ground fault bank determination unit 40, and the current relative to the reference is measured. The phase θ ° is calculated. Since the two ground fault currents Ia and Ib flow in the same direction, they have the same current phase θ ° and have different sizes. When the ground fault bank determination unit 40 determines that the two ground fault currents Ia and Ib are in phase, it determines that the ground fault current flows from the bank B2 to the outside of the bank B3, and the banks B1 and B2 are not the fault occurrence bank. Is determined. In FIG. 1, the ground fault currents Ia and Ib detected by the detection CT1 and CT2 are transmitted by wire to the ground fault bank determination unit 40. However, the detection current may be transmitted wirelessly. The same applies to the other detections CT3 and CT4.

  In addition, the ground fault current Ic is detected by the detection CT3 installed in another parallel connection location 12c, and the rise time of the ground fault current Ic with reference to the reference time signal CP is measured by the ground fault bank determination unit 40. The current phase with respect to is calculated. Since the ground fault current Ic is a current that flows in the opposite direction to the ground fault currents Ia and Ib, the measured current phase is shifted by 180 ° (θ ° + 180 °). When the ground fault bank determination unit 40 determines that the two ground fault currents Ib and Ic across the bank B3 are in opposite phases, the ground fault currents Ib and Ic are obtained from both the banks B2 and B4 adjacent to the bank B3. It is determined that the current flows in, and the bank B3 is specified as a ground fault occurrence bank.

  In addition, the ground fault current Id is detected by the detection CT4 installed at the parallel connection point 12d, and the rise time of the ground fault current Id with reference to the reference time signal CP is measured by the ground fault bank determination unit 40, and the current relative to the reference is measured. Calculate the phase. Since the ground fault current Id here is a current that flows in the same direction as the ground fault current Ic, the measured current phase is (θ ° + 180 °). The ground fault bank determination unit 40 determines that the two ground fault currents Ic and Id in the bank B4 are in phase, and determines that the bank B4 and further the bank B5 are not the ground fault occurrence bank.

  The ground fault current detection at the four parallel connection points 12a to 12c can be performed simultaneously or sequentially. When performing simultaneously, detection CT1-CT4 is installed in each parallel connection location 12a-12c, it determines whether a current phase is an in-phase and an antiphase with each track | line, and specifies a ground fault generation bank. When performing sequentially, it can carry out, for example using only one detection CT1. Further, the two detection CT1 and CT2 are simultaneously used to determine whether or not the bank B2 is a ground fault occurrence bank. If it is determined that the bank is not a ground fault occurrence bank, the two sets are moved to another bank B. It is also effective. In addition, the order of ground fault current detection and phase measurement in the five banks B1 to B5 is not limited to the above example, but is arbitrary. If the ground fault current detection and phase measurement are first performed in the ground fault occurrence bank B3 and the two ground fault currents Ib and Ic are out of phase and are determined to be the ground fault occurrence bank, The ground fault current detection and phase measurement are not necessarily required. In this case, it is desirable to perform ground fault current detection and phase measurement in another bank for higher accuracy.

  The reference time signal generation unit 30 shown in FIG. 1 responds to this fluctuation even if the same slight fluctuation occurs in the commercial power supply frequency of the bank B which is a low-voltage AC distribution line and the frequency of the ground fault current flowing through the common ground line 5. Thus, the frequency of the reference time signal CP synchronized with the commercial power supply fluctuates. Therefore, even if the order of the ground fault current detection and the phase measurement in each of the banks B1 to B5 is temporally different, the phase measurement of the ground fault current can always be determined with high accuracy and whether it is in phase or reverse phase.

  As the reference time signal generating unit 30, in addition to the pulse superimposition type shown in FIG. 1, for example, a type using the GPS receiver 35 shown in FIG. 3 or a type using the pulse oscillation circuit 37 shown in FIG. .

  The reference time signal generator 30 shown in FIG. 3 receives a GPS signal transmitted from a GPS satellite of the global positioning system (GPS) by the GPS receiver 35 through the antenna 36. A reference time signal CP synchronized with the received GPS signal is generated and transmitted to the ground fault bank determination unit 40. The ground fault bank determination unit 40 uses the reference time signal CP generated from the GPS signal as an absolute time to measure the ground fault current phase.

  In the case of the GPS reference time method of FIG. 3, the phase of the ground fault current is simultaneously measured at two or more locations at the same time. For example, as shown in FIG. 3, a detection CT1 is installed at a parallel connection location 12a, and a ground fault bank determination unit 40, a phase data receiver 41, and a reception antenna 42 are attached to the detection CT1. A detection CT4 is installed at another parallel connection location 12d, and a phase data transmitter 43 and a transmission antenna 44 are attached to this detection CT4. A reference time signal CP at the same time is generated by the GPS receiver 35 at each of the parallel connection points 12a and 12d. For example, as shown in FIG. 4, the rise time of the ground fault current Ia of the detected CT1 with reference to the reference time signal CP1 of 12:00:00 is measured, the current phase θ1 ° with respect to the reference is calculated, and the phase Data is transmitted to the ground fault bank determination unit 40 by wire. Similarly, the rise time of the ground fault current Id of the detected CT4 with reference to the reference time signal CP1 of 12:00:00 is measured, the current phase (θ1 ° + 180 °) with respect to the reference is calculated, and the phase data is obtained. Wireless transmission is performed from the transmitter 43 and the transmission antenna 44 to the reception antenna 42 and the receiver 41 of the ground fault bank determination unit 40, and wired transmission is performed from the receiver 1 to the ground fault bank determination unit 40. In this case, the ground fault bank determination unit 40 determines that the ground fault currents at the two parallel connection points 12a and 12d are in reverse phase, determines that the bank B1 and the bank B5 are not the ground fault occurrence bank, and determines that the bank B1 and the bank B It is determined that there is a ground fault occurrence bank inside B5. Similarly, for example, the current phase (θ2 ° + 180 °) of the ground fault current Ia of the detected CT1 with respect to the reference time signal CP2 of 12:00:01 is calculated, and the same reference of 12:00:01 is calculated. The current phase θ2 ° of the ground fault current Id of the detection CT4 with respect to the time signal CP2 is calculated. Also in this case, the ground fault bank determination unit 40 determines that the ground fault currents at the two parallel connection locations 12a and 12d are in reverse phase, and determines that there is a ground fault occurrence bank inside the banks B1 and B5. In FIG. 3, one ground fault bank determination unit 40 determines whether the ground fault currents at the two parallel connection locations are in-phase or reverse phase. One ground fault bank is provided at each of the two parallel connection locations. A fault bank determination unit may be installed, and data may be communicated with each other, and each ground fault bank determination unit may determine whether the two ground fault currents are in phase or reverse phase.

  The reference time signal generator 30 shown in FIG. 5 oscillates a pulse signal having a frequency of 1 / n obtained by dividing the commercial frequency of the low-voltage AC distribution line by an integer n by a single high-frequency pulse oscillation circuit 37, and synchronizes with this pulse signal. The ground reference bank determination unit 40 uses the reference time signal CP thus made. In this case, it is desirable from the point of view of accuracy and practical use that n = 1 or n = 2 to transmit the pulse signal at the zero cross of the commercial voltage.

  The above embodiment is a ground fault bank that is applied to a multiple grounding type low voltage AC distribution line in which B type grounding wires of a plurality of banks that supply power to low voltage consumers such as houses and factories are connected in parallel with a common grounding wire. The identification method and the ground fault bank identification device. The present invention can be applied not only to the multiple grounding type low voltage AC distribution line.

It is a circuit diagram which shows the outline | summary of the low voltage | pressure AC distribution line which shows embodiment of the ground fault generation bank specific device which concerns on this invention. FIG. 2 is a voltage / current waveform diagram for explaining a ground fault current phase measuring method by the ground fault occurrence bank identification device of FIG. 1. It is a circuit diagram which shows the outline | summary of the low voltage | pressure AC distribution line which shows other embodiment. It is a ground fault current waveform diagram for demonstrating the ground fault current phase measuring method by the ground fault generation bank specific apparatus of FIG. It is a circuit diagram which shows the outline | summary of the low voltage | pressure AC distribution line which shows other embodiment.

Explanation of symbols

1 Low voltage AC distribution line 4 Grounding line 5 Joint grounding line B Bank (post transformer)
Ia to Id Ground fault current 10 Ground fault generation bank identification device 12a to 12d Parallel connection point 20 Ground fault current detection unit 30 Reference time signal generation unit 31 Zero cross detection circuit 32 Pulse generation circuit 33 Superimposed current transformer 35 GPS receiver 36 Antenna 37 Transmitter circuit 40 Ground fault bank determination unit CP Reference time signal CT Current transformer

Claims (7)

A method for identifying a bank corresponding to any ground fault occurrence low voltage AC distribution line in a distribution system in which a plurality of banks of low voltage AC distribution lines are connected in parallel,
Detecting a ground fault current in each of the parallel connection points where the load current between the plurality of low-voltage AC distribution lines does not flow, measuring the phase of each detected ground fault current based on a common reference time signal, A method for identifying a ground fault occurrence bank, comprising: identifying a bank corresponding to a ground fault generating low-voltage AC distribution line based on determination of whether a phase of a ground fault current at an adjacent parallel connection point is in phase or reverse phase.   The ground fault occurrence bank identification method according to claim 1, wherein the reference time signal is generated based on a pulse signal synchronized with a commercial power source of the low-voltage AC distribution line.   The ground fault occurrence bank identification method according to claim 2, wherein the pulse signal is superimposed on a plurality of the parallel connection locations.   2. The ground according to claim 1, wherein the reference time signal is generated based on a pulse signal from a pulse oscillation circuit that oscillates a pulse signal at a frequency obtained by dividing a commercial frequency of the low-voltage AC distribution line by an integer. How to identify the bank where the tangle occurred.   The ground fault occurrence bank identification method according to claim 1, wherein the reference time signal is generated based on a GPS signal of a global positioning system. An apparatus for identifying a bank corresponding to any ground fault occurrence low voltage AC distribution line in a distribution system in which low voltage AC distribution lines of a plurality of banks are connected in parallel,
A ground-fault current detection unit that detects a ground-fault current that flows through the parallel connection point at each of the parallel connection points between the low-voltage AC distribution lines, and measures the phase of each ground-fault current detected at the parallel connection point. A reference time signal generation unit that generates a common reference time signal serving as a reference for determining whether the phase of the ground fault current at the adjacent parallel connection point is in phase or opposite to each other, A ground fault occurrence bank identifying device, comprising: a ground fault bank determination unit that determines a bank sandwiched between parallel connection locations as a ground fault occurrence bank.   The ground fault generation according to claim 6, wherein the reference time signal generation unit includes a superimposed current transformer that superimposes a high-frequency pulse current synchronized with a commercial power source of the low-voltage AC distribution line on the parallel connection portion. Bank specific device.

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