JP5094455B2 - Zero-phase current differential relay - Google Patents

Description

  The present invention relates to a zero-phase current differential relay using zero-phase currents at both ends of a power transmission line.

  The conventional current differential relay is composed of three phase current differential relay elements corresponding to each phase and a zero-phase current differential relay element capable of detecting one-phase failure with high sensitivity. In a conventional current differential relay, in the case of a single-phase fault in a power transmission line, if a fault current exceeding the detection sensitivity of the phase current differential relay element of each phase flows, the phase current differential corresponding to the fault phase A control signal (relay output) is output to the breaker in the fault phase by the operation of the relay element. Thereby, the power transmission line is cut off only in the failure phase, and the failure of the power transmission line is removed.

  However, the conventional current differential relay cannot detect a fault in which the fault current is less than the operation sensitivity of the current differential relay. In this case, it is possible to detect a fault by using a higher-sensitivity zero-phase current differential relay element, but the zero-phase current differential relay element cannot identify the fault phase. For this reason, a small ground fault current that does not operate with the phase current differential relay element performs a three-phase operation, which interrupts all three phases of the power transmission line. In order to improve such a problem, in the conventional power differential relay, the output of the zero-phase current differential relay element is delayed from the output of the phase current differential relay element and output.

  In addition, as a conventional technique for determining a failure phase due to a one-phase ground fault, the minimum failure voltage among the three-phase voltage and the phase in which the reference phase of the zero-phase current and the reverse-phase current on the own end side is substantially the same phase Patent Document 1 discloses a technique for determining that the phase is a one-phase ground fault when the phases match.

JP 2004-364376 A

  However, in the prior art described in Patent Document 1, depending on the system conditions, the failure current on the own end side is small, and even if the zero-phase current differential relay element operates, the determination of the one-phase ground fault cannot be performed correctly. Therefore, the determination by the self-end current may be an unnecessary restriction on the operation of the zero-phase current differential relay.

  Further, in the fault phase determination described in Patent Document 1, the zero-phase current differential relay itself requires 3 to determine whether or not it is a one-phase ground fault even though no voltage input is required. Since voltage determination such as determining the minimum voltage phase among the phase voltages is necessary, there is a problem that voltage information must be input.

  The present invention has been made in view of the above, and even when the fault current on the end side is small, a ground fault that has occurred in the power transmission line is detected in one phase ground without performing voltage determination. It is an object of the present invention to obtain a zero-phase current differential relay that can determine whether or not there is a fault and reliably determine the fault phase.

  In order to solve the above-described problems and achieve the object, the present invention provides a zero-phase current of a three-phase current on a self-end obtained from a self-current transformer and a counterpart end obtained from a counterpart current transformer. In the zero-phase current differential relay including a determination unit that determines the presence or absence of a ground fault in the power line transmission line based on a differential calculation result based on the zero-phase current of the side three-phase current, the determination unit includes the determination unit Positive-phase synthesis for obtaining a positive-phase current using each phase as a reference phase based on a synthesized current for each phase obtained by synthesizing the same-phase current of the self-side three-phase current and the counterpart-side three-phase current And a reverse phase current with each phase as a reference phase based on the combined current of each phase obtained by synthesizing the current of the same phase of the local end side three phase current and the counterpart end side three phase current A composite zero phase is obtained by synthesizing the reverse phase synthesis unit to be obtained, the zero phase current of the local end side three phase current, and the zero phase current of the counter end side three phase current. A ground fault that occurs on the power transmission line based on the positive phase current, the negative phase current, and the composite zero phase current is a one-phase ground fault. It is characterized by determining whether or not and determining the failure phase.

  According to the present invention, the difference based on the zero-phase current of the self-side three-phase current obtained from the self-current transformer and the zero-phase current of the counterpart three-phase current obtained from the counterpart current transformer. When a ground fault in the power line transmission line is detected based on the dynamic calculation result, the current of each phase obtained by synthesizing the current of the same phase of the local end side three-phase current and the counterpart end side three-phase current is obtained. Each based on the combined current of each phase obtained by combining the positive phase current with each phase based on the combined current as the reference phase and the same phase current of the self-end side three-phase current and the opposite end side three-phase current On the power transmission line based on the reverse phase current with the phase as the reference phase and the combined zero phase current of the zero phase current of the local end side three phase current and the zero phase current of the counterpart end side three phase current In order to determine whether or not the ground fault that has occurred is a one-phase ground fault, and to determine the fault phase, Even if it is a case, the zero-phase current can reliably determine whether the ground fault that has occurred in the power transmission line is a one-phase ground fault together with the fault phase, without performing voltage determination There is an effect that a differential relay can be obtained.

  Embodiments of a zero-phase current differential relay according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a configuration of a power system to which a zero-phase current differential relay according to the present invention is applied. In FIG. 1, the power system includes a power transmission line 1 connected to a power source E1 and a power source E2, and current transformers 2 (2-1 and 2-2 are shown) at both ends of the power transmission line 1. Is installed, detects the presence or absence of a failure on the power transmission line 1 by taking in the secondary current of the current transformer 2, and based on the detection result, the circuit breakers installed at both ends of the power transmission line 1 ( A zero-phase current differential relay 3 (shown as 3-1 and 3-2) that controls the power transmission line 1 by controlling the power transmission line 1 (not shown). In FIG. 1, a current transformer 2-1 is disposed on the power source E1 side, a current transformer 2-2 is disposed on the power source E2 side, and a zero-phase current differential relay 3-1 is connected to the current transformer 2-1. The secondary current is taken in, and the zero-phase current differential relay 3-2 is configured to take in the secondary current of the current transformer 2-2.

  The zero-phase current differential relay 3 is a current transformer 2 on its own end (in the case of the zero-phase current differential relay 3-1, it is the current transformer 2-1, in the case of the zero-phase current differential relay 3-2). Takes in the current from the current transformer 2-2), and uses the current value of the taken-in current as current information as a zero-phase current differential relay 3 (zero-phase in the case of the zero-phase current differential relay 3-1) The current differential relay 3-2 is provided with a communication function for transmitting to the zero-phase current differential relay 3-1) in the case of the zero-phase current differential relay 3-2. The zero-phase current differential relay 3 has a fault on the power transmission line 1 based on the current from the current transformer 2 on the own end side and the current information received from the zero-phase current differential relay 3 on the other end side. A ratio differential calculation is performed to detect the presence or absence of occurrence of a fault, and a control signal for controlling the circuit breaker is output based on the ratio differential calculation result.

  FIG. 2 is a block diagram showing a configuration of the zero-phase current differential relay 3 shown in FIG. The zero-phase current differential relay is a constituent element as one of the transmission line protection relay elements for detecting a failure on the power transmission line 1, but here, the zero-phase current difference relay is the main point of the present invention. Only the configuration relating to the dynamic relay element and its single phase operation will be described.

  In FIG. 2, the zero-phase current differential relay 3 includes an input current conversion unit 4 (showing 4A, 4B, and 4C), a transmission unit 17, a receiving unit 5, and a reception current conversion unit 6 (showing 6A, 6B, and 6C). , Current time synchronizer 7, combiner 8 (indicating 8A, 8B, 8C), positive phase combiner 11, reverse phase combiner 12, own end zero phase combiner 9, counterpart zero phase combiner 10, zero at both ends A phase combining unit 13, a zero-phase current differential relay element unit 14, a failure phase determination unit 15, and an AND circuit 16 (16A, 16B, 16C, 16BC, 16CA, and 16AB are shown) are provided.

  The input current conversion unit 4A transmits A-phase self-end current data I1A obtained by performing conversion processing on the A-phase self-end current IA of the three-phase inputs input from the self-end current transformer 2. To the unit 17 and the current time synchronization unit 7. The input current conversion unit 4B transmits the B-phase self-current data I1A obtained by performing the conversion process on the B-phase self-current IB among the three-phase inputs input from the self-current transformer 2. To the unit 17 and the current time synchronization unit 7. The input current conversion unit 4C transmits C-phase self-current data I1C obtained by performing conversion processing on the C-phase self-current IC out of the three-phase input input from the self-current transformer 2. To the unit 17 and the current time synchronization unit 7. In the conversion process, the self-current I (IA, IB, IC) of the phase from the current transformer 2 on the self-end side is taken into the zero-phase current differential relay 3 and the zero-phase current differential relay 3 This is a process of converting into current data to be handled. Specifically, the current I is captured and insulated from the secondary side of the current transformer 2, the harmonics of the captured current are removed, and the self-current I from which the harmonics have been removed is represented as digital current self-current data. Convert to I1 (indicating I1A.I1B, I1C).

  The transmission unit 17 has a communication interface with the zero-phase current differential relay 3 on the counterpart end side, and the current data I1 input from the input current conversion unit 4 is sent to the counterpart zero-phase current differential relay 3 as current information. Send. As the communication interface, for example, PCM (Pulse Code Modulation) transmission is used.

  The receiving unit 5 has a communication interface with the zero-phase current differential relay 3 on the counterpart end side, and receives current information from the transmission unit 17 of the zero-phase current differential relay 3 on the counterpart end side. The receiver 5 outputs the received current information to the received current converter 6 and notifies the current time synchronizer 7 that the current information has been received.

  The reception current conversion unit 6A extracts the A-phase self-terminal current data I1A of the counterpart zero-phase current differential relay 3 from the current information input from the reception unit 5, and synthesizes it as the A-phase counterpart current data IR1A. To the unit 8A and the counterpart zero phase synthesis unit 10. The reception current converter 6B extracts the B-phase self-terminal current data I1B of the counterpart zero-phase current differential relay 3 from the current information input from the receiver 5, and synthesizes it as B-phase counterpart current data IR1B. To the unit 8B and the mating zero phase synthesis unit 10. The reception current conversion unit 6C extracts the C-phase self-current data I1C of the counterpart zero-phase current differential relay 3 from the current information input from the reception unit 5 and synthesizes it as C-phase counterpart current data IR1C. To the unit 8C and the mating terminal zero-phase synthesis unit 10.

  The current time synchronization unit 7 corrects the propagation delay time of the current of the counterpart zero-phase current differential relay 3 based on the notification that the current information is received from the reception unit 5, and the received current conversion unit 6 The time relationship between the counterpart current data IR1 (indicating IR1A, IR1B, IR1C) to be output and the local current data I1 output by the input current converter 4 is synchronized, and the synchronized local current data I2 (I2A, (I2B and I2C are shown) are output to the combining unit 8 and the self-end zero phase combining unit 9.

  The synthesizing unit 8 obtains a vector sum of the own end current data I2 for each phase input from the current time synchronization unit 7 and the other end current data IR1 for each phase input from the reception current conversion unit 6, The obtained vector sum is output to the normal phase synthesizing unit 11 and the negative phase synthesizing unit 12 as synthesized current data IS (indicating IAS, IBS, ICS) of the phase. The combining unit 8A outputs the vector sum of the A-phase self-terminal current data I2A and the A-phase counterpart terminal current data IR1A to the positive-phase combining unit 11 and the negative-phase combining unit 12 as the A-phase combined current IAS. The synthesizer 8B outputs the vector sum of the B-phase self-terminal current data I2B and the B-phase counterpart current data IR1B to the positive-phase synthesizer 11 and the negative-phase synthesizer 12 as a B-phase synthesized current IBS. The combining unit 8C outputs the vector sum of the C-phase self-terminal current data I2C and the C-phase counterpart terminal current data IR1C to the positive-phase combining unit 11 and the negative-phase combining unit 12 as a C-phase combined current ICS.

The positive phase combining unit 11 combines the positive phase current data I1S (I1SA, I1SB) of each phase based on the combined current data IS for each phase input from the combining unit 8 with each phase as a reference phase. , Indicating I1SC). Here, assuming that the combined current data of the A phase is IAS, the combined current data of the B phase is IBS, and the combined current data of the C phase is ICS, the positive phase current data I1SA of the combined current with the A phase as the reference phase is ,
I1SA = (IAS + IBS∠120 ° + ICS∠240 °) / 3 (Formula 1)
Can be expressed as
Further, the positive phase current data I1SB of the combined current with the B phase as the reference phase is
I1SB = (IAS∠240 ° + IBS + ICS∠120 °) / 3 (Formula 2)
Can be expressed as
Further, the positive phase current data I1SC of the combined current with the C phase as the reference phase is
I1SC = (IAS∠120 ° + IBS∠240 ° + ICS) / 3 (Formula 3)
Can be expressed as
The positive phase synthesizing unit 11 obtains the positive phase current data I1S based on each phase using the above (Equation 1) to (Equation 3), and outputs the obtained positive phase current data I1S to the failure phase determination unit 15. .

Based on the combined current data IS for each phase input from the combining unit 8, the negative phase combining unit 12 combines the negative phase current data I 2 S (I 2 SA, I 2 SB) for each phase using the respective phases as reference phases. , Indicating I2SC). Here, assuming that the combined current data of the A phase is IAS, the combined current data of the B phase is IBS, and the combined current of the C phase is ICS, the reverse phase current data I2SA of the combined current with the A phase as the reference phase is
I2SA = (IAS + IBS∠240 ° + ICS∠120 °) / 3 (Formula 4)
Can be expressed as
Further, the reverse-phase current data I2SB of the combined current with the B phase as the reference phase is
I2SB = (IAS∠120 ° + IBS + ICS∠240 °) / 3 (Formula 5)
Can be expressed as
Further, the reverse current data I2SC of the combined current with the C phase as the reference phase is
I2SC = (IAS∠240 ° + IBS∠120 ° + ICS) / 3 (Formula 6)
Can be expressed as
The reverse phase synthesis unit 12 obtains the reverse phase current data I2S based on each phase using the above (Formula 4) to (Formula 6), and outputs the obtained reverse phase current data I2S to the fault phase determination unit 15. .

  The self-end zero-phase synthesizing unit 9 synthesizes the zero-phase current of the synchronized self-end current data I <b> 2 input from the current time synchronization unit 7. The self-end zero-phase combining unit 9 outputs the combined current to the both-end zero-phase combining unit 13 and the zero-phase current differential relay element unit 14 as self-end combined zero-phase current data I0L.

  The mating terminal zero-phase combining unit 10 combines the zero-phase current of the mating terminal current data IR1 input from the reception current converting unit 6. The other end zero-phase combining unit 10 outputs the combined current as the other end combined zero-phase current data I0R to the both-ends zero-phase combining unit 13 and the zero-phase current differential relay element unit 14.

  The both-ends zero-phase synthesizing unit 13 synthesizes the own-end synthesized zero-phase current data I0L input from the own-end zero-phase synthesizing unit 9 and the other-end synthesized zero-phase current data I0R input from the other-end zero-phase synthesizing unit 10. To do. The both-ends zero-phase combining unit 13 outputs the combined current data to the failure phase determining unit 15 as combined zero-phase current data I0S.

  The zero-phase current differential relay element unit 14 includes a self-end combined zero-phase current data I0L input from the self-end zero-phase combining unit 9 and a counter-end combined zero-phase current data input from the counter-end zero-phase combining unit 10. A differential operation is performed based on I0R, and the differential operation result is output to the AND circuit 16 and output to the outside as a zero-phase current differential relay element output.

  The failure phase determination unit 15 includes normal phase current data I1S for each phase input from the normal phase synthesis unit 11, reverse phase current data I2S for each phase input from the negative phase synthesis unit 12, and zero-phase synthesis at both ends. Based on the combined zero-phase current data I0S input from the unit 13, whether or not a failure has occurred on the power transmission line 1 and the failure phase when a failure has occurred are determined. The failure phase determination unit 15 uses the determination output OA when it is determined that the phase A is a single-phase ground fault (uses “effective” in the sense that a signal for performing a control operation is output, and so on. ) And other determination outputs OB, OC, OBC, OCA, OAB are disabled (“invalid” is used in the sense that a signal for performing a control operation is not output, and so on). The failure phase determination unit 15 enables the determination output OB and disables the other determination outputs OA, OC, OBC, OCA, and OAB when determining that it is a B-phase one-phase ground fault. The failure phase determination unit 15 validates the determination output OC and invalidates the other determination outputs OA, OB, OBC, OCA, and OAB when it is determined that a C-phase one-phase ground fault has occurred.

  If the failure phase determination unit 15 determines that the two-phase ground fault has occurred in the BC phase, the failure phase determination unit 15 enables the determination output OBC and disables the other determination outputs OA, OB, OC, OCA, and OAB. When the failure phase determination unit 15 determines that a CA phase two-phase ground fault has occurred, the failure phase determination unit 15 enables the determination output OCA and disables the other determination outputs OA, OB, OC, OBC, and OAB. If the failure phase determination unit 15 determines that the AB phase two-phase ground fault has occurred, the failure phase determination unit 15 enables the determination output OAB and disables the other determination outputs OA, OB, OC, OBC, and OCA.

  The AND circuit 16 includes a determination output O (indicating OA, OB, OC, OBC, OCA, OAB) indicating the determination result of each phase input from the failure phase determination unit 15, and a zero-phase current differential relay element unit 14. Is output as the operation determination results AΦT, BΦT, CΦT, BCΦT, CAΦT, ABΦT for each phase. Note that the failure phase determination unit 15 and the AND circuit 16 described above provide the function of the determination unit in the present invention.

  Next, the operation of the zero-phase current differential relay 3 of the first embodiment will be described. The input current conversion unit 4 performs a conversion process on the current I of the phase among the three-phase inputs input from the current transformer 2 on the own end side. Self-end current data I 1 obtained by subjecting the current I of the phase to conversion processing is output to the transmitter 17 and the current time synchronizer 7. The transmission unit 17 transmits the own-end current data I1 input from the input current conversion unit 4 to the zero-phase current differential relay 3 on the other end side as current information.

  On the other hand, the receiving unit 5 receives the current information transmitted by the transmitting unit 17 of the zero-phase current differential relay 3 on the other end side, outputs the received current information to the received current converting unit 6, and receives the current information. The current time synchronization unit 7 is notified of the fact. The reception current converter 6 extracts the other end current data in the corresponding phase of the zero-phase current differential relay 3 on the other end side from the current information, and uses the extracted opposite end current data as the other end current data IR1 corresponding to the relevant phase. Output to the synthesizing unit 8 and the counterpart zero-phase synthesizing unit 10.

  The current time synchronization unit 7 corrects the propagation delay time of the current of the counterpart zero-phase current differential relay 3 based on the notification that the current information is received from the reception unit 5, and The time relationship with the own end current data I1 is synchronized, and the synchronized own end current data I2 is output to the combining unit 8 and the own end zero phase combining unit 9 corresponding to the phase.

  The synthesizing unit 8 obtains a vector sum of the self-terminal current data I2 of the phase and the counter-end current data IR1 of the phase, and uses the obtained vector sum as the synthetic current data IS of the phase and the negative phase synthesizing unit 11 The data is output to the synthesis unit 12.

  The positive phase synthesis unit 11 obtains the positive phase current data I1S of the synthesized current with each phase as the reference phase by the above (Formula 1) to (Formula 3) using the synthesized current data IS for each phase, and determines the failure phase. To the unit 15. The reverse phase synthesis unit 12 obtains the reverse phase current data I2S of the synthesized current with each phase as the reference phase by the above (Formula 4) to (Formula 6) using the composite current data IS for each phase and determines the failure phase. To the unit 15.

  The self-end zero-phase combining unit 9 combines the self-end combined zero-phase current data I0L obtained by combining the zero-phase currents of the self-end current data I2 of each phase input from the current time synchronization unit 7 with both-ends zero-phase combining. Output to the unit 13 and the zero-phase current differential relay element unit 14. The opposite end zero-phase combining unit 10 combines the opposite end combined zero-phase current data I0R obtained by combining the zero-phase currents of the opposite-end current data IR1 of each phase input from the reception current converting unit 6 into both-ends zero-phase combining. Output to the unit 13 and the zero-phase current differential relay element unit 14.

  The both-ends zero-phase combining unit 13 outputs combined zero-phase current data I0S obtained by combining the self-end combined zero-phase current data I0L and the combined zero-phase current data I0R to the failure phase determining unit 15. The zero-phase current differential relay element unit 14 performs a differential operation based on the self-end composite zero-phase current data I0L and the counterpart end composite zero-phase current data I0R, and outputs the differential operation result to the AND circuit 16. Output to the outside as zero-phase current differential relay element output.

  The failure phase determination unit 15 determines whether a failure has occurred on the power transmission line 1 based on the positive phase current data I1S for each phase, the reverse phase current data I2S for each phase, and the combined zero phase current data I0S. And the failure phase when a failure occurs is determined.

  The determination processing operation of the failure phase determination unit 15 will be described in detail with reference to the flowchart of FIG. The failure phase determination unit 15 determines whether or not the combined zero-phase current data I0S is larger than a predetermined threshold value ε1 (step S100). Here, the threshold value ε1 is a value indicating a sensitivity equivalent to the zero-phase difference current relay element sensitivity of the zero-phase current differential relay element unit 14, or is equal to or greater than the zero-phase difference current relay element sensitivity of the zero-phase current differential relay element unit 14. To do.

  When the combined zero-phase current data I0S is larger than the threshold value ε1 (step S100, Yes), the failure phase determination unit 15 determines whether the combined zero-phase current data I0S and the reverse-phase current data I2SA for the combined current with the A phase as the reference phase. It is determined whether or not the phase difference is within the operating range. When it is determined that the phase difference between the combined zero-phase current data I0S and the reverse-phase current data I2SA with respect to the combined current with the A phase as the reference phase is not within the operating region (No in step S101), the failure phase determination unit 15 Determines whether or not the phase difference between the combined zero-phase current data I0S and the reverse-phase current data I2SB with respect to the combined current with the B phase as a reference phase is within the range of the operation region (step S102).

  When it is determined that the phase difference between the combined zero-phase current data I0S and the reversed-phase current data I2SB with respect to the combined current with the B phase as the reference phase is not within the operating region (No in step S102), the failure phase determination unit 15 Determines whether or not the phase difference between the combined zero-phase current data I0S and the reversed-phase current data I2SC with respect to the combined current with the C-phase as a reference phase is within the range of the operating region (step S103).

  When it is determined that the phase difference between the combined zero-phase current data I0S and the reversed-phase current data I2SC with respect to the combined current with the C phase as the reference phase is within the operating region (step S103, Yes), the failure phase determination unit 15 Determines whether the phase difference between the negative phase current data I2SC for the combined current with the C phase as the reference phase and the positive phase current data I1SC for the combined current with the C phase as the reference phase is within the operating range (Step S104).

  When it is determined that the phase difference between the negative phase current data I2SC with respect to the combined current with the C phase as the reference phase and the positive phase current data I1SC with respect to the combined current with the C phase as the reference phase is within the operating region (step S104) , Yes), the failure phase determination unit 15 enables only the determination output OC indicating the C-phase one-phase ground fault determination, and disables the other determination outputs OA, OB, OBC, OCA, and OAB (step S105). ).

  When it is determined that the phase difference between the negative phase current data I2SC with respect to the combined current with the C phase as the reference phase and the positive phase current data I1SC with respect to the combined current with the C phase as the reference phase is not within the operating range (step S104) , No), the failure phase determination unit 15 enables only the determination output OAB indicating the AB phase two-phase ground fault determination, and disables the other determination outputs OA, OB, OC, OBC, OCA (step S106). ).

  On the other hand, when the combined zero-phase current data I0S is less than the threshold value ε1 (step S100, No), or the phase difference between the combined zero-phase current data I0S and the reverse-phase current data I2SC with respect to the combined current with the C phase as the reference phase is When it determines with it not being in the range of an operation area | region (step S103, No), the failure phase determination part 15 determines with the ground fault not having generate | occur | produced on the power transmission line 1, and all determination output OA. , OB, OC, OBC, OCA, OAB are invalidated (step S107).

  On the other hand, when it is determined that the phase difference between the combined zero-phase current data I0S and the reverse-phase current data I2SB with respect to the combined current with the B phase as the reference phase is within the operating range (step S102, Yes), the failure phase determination The unit 15 determines whether or not the phase difference between the negative phase current data I2SB for the combined current with the B phase as the reference phase and the positive phase current data I1SB with respect to the combined current with the B phase as the reference phase is within the operating range. Is determined (step S108).

  When it is determined that the phase difference between the negative phase current data I2SB for the combined current with the B phase as the reference phase and the positive phase current data I1SB with respect to the combined current with the B phase as the reference phase is within the operating region (step S108) , Yes), the failure phase determination unit 15 enables only the determination output OB indicating the B-phase one-phase ground fault determination, and disables the other determination outputs OA, OC, OBC, OCA, OAB (step S109). ).

  When it is determined that the phase difference between the negative phase current data I2SB for the combined current with the B phase as the reference phase and the positive phase current data I1SB with respect to the combined current with the B phase as the reference phase is not within the range of the operating region (step S108) , No), the failure phase determination unit 15 enables only the determination output OCA indicating the CA phase two-phase ground fault determination, and disables the other determination outputs OA, OB, OC, OBC, OAB (step S110). ).

  On the other hand, if it is determined that the phase difference between the combined zero-phase current data I0S and the reverse-phase current data I2SA with respect to the combined current with the A phase as the reference phase is within the operating region (Yes in step S101), the failure phase determination The unit 15 determines whether or not the phase difference between the negative phase current data I2SA for the combined current with the A phase as the reference phase and the positive phase current data I1SA for the combined current with the A phase as the reference phase is within the operating range. Is determined (step S111).

  When it is determined that the phase difference between the negative phase current data I2SA for the combined current with the A phase as the reference phase and the positive phase current data I1SA with respect to the combined current with the A phase as the reference phase is within the operating region (step S111) , Yes), the failure phase determination unit 15 enables only the determination output OA indicating the A-phase one-phase ground fault determination and disables the other determination outputs OB, OC, OBC, OCA, OAB (step S112). ).

  When it is determined that the phase difference between the negative phase current data I2SA for the combined current with the A phase as the reference phase and the positive phase current data I1SA with respect to the combined current with the A phase as the reference phase is not within the operating range (step S111) , No), the failure phase determination unit 15 enables only the determination output OBC indicating the BC phase two-phase ground fault determination, and disables the other determination outputs OA, OB, OC, OCA, and OAB (step S113). ).

  As described above, the failure phase determination unit 15 determines that the combined zero-phase current data I0S is equal to or greater than the threshold value ε1, and the combined zero-phase current data I2SA is obtained by using the A-phase as a reference phase for the combined zero-phase current data I0S. Which reference phase of the reversed-phase current data I2SB of the combined current with the B phase as the reference phase and the reversed-phase current data I2SC of the combined current with the C-phase as the reference phase enters the operation region It is determined, and it is determined whether or not the phase difference between the negative phase current data I2S entering the operation region and the positive phase current data I1S of the relevant phase enters the operation region. In comparison between I1S and I2S in the phase reference, the failure phase determination unit 15 determines that the positive phase current data I1S of the phase is less than ± 90 degrees relative to the negative phase current data I2S of the phase, that is, the same phase The case where the relationship is closer to the reverse phase is determined as the operation. When the determination result is an operation output, the failure phase determination unit 15 determines that the phase is a failure phase and outputs it as a one-phase ground fault. On the other hand, when the determination result is not an operation output, since the phase corresponds to a healthy phase, two phases other than the phase are determined as a failure phase and output as a two-phase ground fault. The operation region is set to a value such that any one of the reference phases of the A phase, the B phase, and the C phase falls within the operation region.

  The AND circuit 16A outputs a logical product of the zero-phase current differential relay element output and the determination output OA of the failure phase determination unit 15 as an output AΦT, and the AND circuit 16B outputs the zero-phase current differential relay element output and the failure phase. A logical product of the determination output OB of the determination unit 15 is output as an output BΦT, and the AND circuit 16C outputs a logical product of the zero-phase current differential relay element output and the determination output OC of the failure phase determination unit 15 as an output CΦT. The AND circuit 16BC outputs a logical product of the zero-phase current differential relay element output and the determination output OBC of the failure phase determination unit 15 as an output BCΦT, and the AND circuit 16CA outputs the zero-phase current differential relay element output and A logical product with the determination output OCA of the failure phase determination unit 15 is output as an output CAΦT, and the AND circuit 16AB discusses the zero-phase current differential relay element output and the determination output OAB of the failure phase determination unit 15 The logical product is output as output ABΦT.

  Next, the correctness of the operation of the above-described zero-phase current differential relay 3 will be described with reference to FIGS. 4 and 5. FIG. 4 shows an equivalent circuit in the symmetric coordinate method in the case of a one-phase ground fault in A phase (A phase ground fault). FIG. 5 shows an equivalent circuit in the symmetric coordinate method in the case of a BC-phase two-phase ground fault (BC-phase ground fault). As shown in FIG. 4, in the case of an A-phase ground fault, almost the same phase current flows in the currents I1, I2, and I0. On the other hand, as shown in FIG. 5, in the case of the BC phase ground fault, the current I2 and the current I0 are in phase, but the currents I2 and I1 flow in opposite phases. In addition, when a power line internal failure occurs, if the power supply phases at both ends are substantially equal, the CT polarities are connected to opposite polarities at both ends, so that the phases of the currents I1, I2, and I0 are substantially equal. Therefore, in the case of an A-phase ground fault with respect to the combined current at both ends, the current indicated by the positive-phase current data I1SA, the current indicated by the negative-phase current data I2SA, and the current indicated by the combined zero-phase current data I0S are: The condition that almost the common-mode current flows is established. On the other hand, in the case of a BC phase ground fault, the current indicated by the negative phase current data I2SA and the current indicated by the combined zero phase current data I0S are in phase, but the current indicated by the negative phase current data I2S and the positive phase current data I1S. The condition that the current of the opposite phase flows is established.

  As described above, in the first embodiment, the zero-phase current of the self-end side three-phase current obtained from the self-end current transformer and the counter-end side three-phase current obtained from the counterpart current transformer. When a ground fault in the power line transmission line is detected based on the differential calculation result based on the zero-phase current of the current, the same-phase current of the own end side three-phase current and the other end side three-phase current is synthesized. The positive phase current with each phase as a reference phase based on the combined current (vector sum current of the same phase of the own end and the opposite end) obtained for each phase, the own end side three phase current and the opposite end side 3 The reverse phase current with each phase as the reference phase based on the combined current of each phase obtained by synthesizing the current of the same phase of the phase current, the zero phase current of the own end side three phase current and the opposite end side three phase Based on the combined zero-phase current obtained by synthesizing the zero-phase current of the current, whether or not the ground fault occurring on the power transmission line is a one-phase ground fault is determined. Since the failure phase judgment is performed, even if the local fault current is small, it occurs in the power transmission line without using the voltage input as in the conventional failure phase judgment. It is possible to reliably determine whether or not the detected ground fault is a one-phase ground fault together with the fault phase determination. Further, in the first embodiment, when the phase difference between the reference phase of the negative phase current that substantially matches the phase of the zero phase current and the positive phase current of the reference phase is within the range of the operation region, Since it is determined that a single-phase ground fault has occurred in the phase, even if the fault current on the local end side is extremely small, the voltage input is not used as in the conventional fault phase determination. The fault phase on the transmission line can be reliably detected.

  In the determination processing operation of the failure determination processing unit described with reference to the flowchart of FIG. 3, the combined zero-phase current data I0S and the predetermined threshold value ε1 are compared. Instead of comparing the data I0S with the predetermined threshold value ε1, it may be determined whether the zero-phase current differential relay element output, which is the output of the zero-phase current differential relay element unit 14, is valid or invalid. . In this case, the case where “the zero-phase current differential relay element output is valid” corresponds to the case where “the combined zero-phase current data I0S is greater than the threshold ε1”, and “the zero-phase current differential relay element output is invalid”. This corresponds to the case where “the combined zero-phase current data I0S is equal to or less than the threshold value ε1”.

Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the phase determination is performed based on the normal phase, the reverse phase, and the zero phase calculation by the symmetric coordinate method. In the second embodiment, the α current, β current, and Phase determination based on zero-phase current is performed.

  The configuration of the power system to which the zero-phase current differential relay of the second embodiment is applied is the same as that of the power system of the first embodiment shown in FIG. Instead of -1 and 3-2, zero-phase current differential relays 3a-1 and 3a-2 are used.

  FIG. 6 is a block diagram showing a configuration of the zero-phase current differential relay 3a (shown by 3a-1 and 3a-2) according to the second embodiment. The zero-phase current differential relay 3a of the second embodiment shown in FIG. 6 includes a positive-phase combining unit 11 and a negative-phase combining unit of the zero-phase current differential relay 3 of the first embodiment shown in FIG. 12 and the failure phase determination unit 15 are provided with an α current calculation unit 18, a β current calculation unit 19, and a failure phase determination unit 15a. Components having the same functions as those of the zero-phase current differential relay 3 of the first embodiment shown in FIG. 2 are given the same reference numerals, and redundant description is omitted.

The α current calculation unit 18 obtains α current data for each phase based on the combined current data IS for each phase input from the combining unit 8. Assuming that the combined current data of the A phase is IAS, the combined current data of the B phase is IBS, and the combined current data of the C phase is ICS, the α current data IαSA with the A phase as the reference phase is
IαSA = (2 × IAS-IBS-ICS) / 3 (Formula 7)
Can be expressed as The α current data IαSB with the B phase as the reference phase is
IαSB = (− IAS + 2 × IBS−ICS) / 3 (Formula 8)
Can be expressed as The α current data IαSC with the C phase as the reference phase is
IαSC = (− IAS−IBS + 2 × ICS) / 3 (Formula 9)
Can be expressed as The α current calculation unit 18 obtains α current data IαS (indicating IαSA, IαSB, and IαSC) for each phase using the above (Expression 7) to (Expression 9). The α current calculation unit 18 outputs α current data IαS for each phase to the failure phase determination unit 15a.

The β current calculation unit 19 obtains β current data for each phase based on the combined current data IS for each phase input from the combining unit 8. If the combined current data of the A phase is IAS, the combined current data of the B phase is IBS, and the combined current data of the C phase is ICS, the β current data IβSA with the A phase as the reference phase is
IβSA = (IBS−ICS) × (√3 / 3) (Formula 10)
Can be expressed as The β current data IβSB with the B phase as the reference phase is
IβSB = (ICS−IAS) × (√3 / 3) (Equation 11)
Can be expressed as The β current data IβSC with the C phase as the reference phase is
IβSC = (IAS−IBS) × (√3 / 3) (Equation 12)
Can be expressed as The β current calculation unit 19 obtains β current data IβS (indicating IβSA, IβSB, and IβSC) for each phase using the above (Formula 10) to (Formula 12). The β current calculation unit 19 outputs β current data IβS for each phase to the failure phase determination unit 15a.

  The failure phase determination unit 15 a includes α current data IαS for each phase input from the α current calculation unit 18, β current data IβS for each phase input from the β current calculation unit 19, and both-end zero phase synthesis unit 13. Based on the composite zero-phase current data I0S input from, whether or not a failure has occurred on the power transmission line 1 and the failure phase when a failure has occurred are determined. The failure phase determination unit 15a enables the determination output OA and disables the other determination outputs OB, OC, OBC, OCA, and OAB when determining that the phase A single-phase ground fault has occurred. The failure phase determination unit 15a enables the determination output OB and disables the other determination outputs OA, OC, OBC, OCA, and OAB when determining that it is a B-phase one-phase ground fault. The failure phase determination unit 15a validates the determination output OC and invalidates the other determination outputs OA, OB, OBC, OCA, and OAB when it is determined that a C-phase one-phase ground fault has occurred.

  If the failure phase determination unit 15a determines that a two-phase ground fault has occurred in the BC phase, the failure phase determination unit 15a enables the determination output OBC and disables the other determination outputs OA, OB, OC, OCA, and OAB. If the failure phase determination unit 15a determines that a CA phase two-phase ground fault has occurred, the failure phase determination unit 15a enables the determination output OCA and disables the other determination outputs OA, OB, OC, OBC, and OAB. If the failure phase determination unit 15a determines that it is an AB phase two-phase ground fault, the failure output determination unit 15a enables the determination output OAB and disables the other determination outputs OA, OB, OC, OBC, and OCA.

  Next, the operation of the zero-phase current differential relay 3a of the second embodiment will be described. The difference between the zero-phase current differential relay 3a of the second embodiment and the zero-phase current differential relay 3 of the first embodiment is that the zero-phase current differential relay 3 of the first embodiment is different. In contrast, the phase determination is performed based on the normal phase, the reverse phase, and the zero phase calculation by the symmetric coordinate method, whereas the zero phase current differential relay 3a according to the second embodiment has an α current, β by the Clark coordinate method. The phase determination based on the current and the zero-phase current is performed, and the other operations are the same as those of the zero-phase current differential relay 3 of the first embodiment. explain.

  The α current calculation unit 18 uses the combined current data IS for each phase input from the combining unit 8 to obtain the α current data IαS of each phase according to the above (Expression 7) to (Expression 9), thereby determining the failure phase determination unit. To 15a. The β current calculation unit 19 uses the combined current data IS for each phase input from the combining unit 8 to obtain the β current data IβS of each phase according to the above (Equation 10) to (Equation 12) to determine the failure phase determination unit. To 15a. The both-ends zero-phase combining unit 13 outputs combined zero-phase current data I0S obtained by combining the self-end combined zero-phase current data I0L and the combined zero-phase current data I0R to the failure phase determination unit 15a. The failure phase determination unit 15a determines whether a ground fault has occurred on the power transmission line 1 based on the α current data IαS for each phase, the β current data IβS for each phase, and the combined zero phase current data I0S. , And a fault phase when a ground fault has occurred is determined.

  The determination processing operation of the failure phase determination unit 15a will be described in detail with reference to the flowchart of FIG. It is determined whether or not the combined zero-phase current data I0S is larger than a predetermined threshold value ε1 (step S200). Here, the threshold value ε1 is a value indicating a sensitivity equivalent to the zero-phase difference current relay element sensitivity of the zero-phase current differential relay element unit 14, or is equal to or greater than the zero-phase difference current relay element sensitivity of the zero-phase current differential relay element unit 14. To do.

  When the combined zero-phase current data I0S is larger than the threshold ε1 (step 200, Yes), the failure phase determination unit 15a determines whether or not the β current data IβSA having the A phase as the reference phase is smaller than a predetermined threshold ε2. Determination is made (step S201). When it is determined that the β current data IβSA with the A phase as the reference phase is smaller than the predetermined threshold value ε2 (Yes in step S201), the failure phase determination unit 15a uses the combined zero phase current data I0S and the A phase as the reference phase. It is determined whether or not the phase difference from the α current data IαSA is within the range of the operation region (step S202). That is, it is determined whether or not the α current calculated in the reference phase of the α current with the A phase as the reference phase with respect to the current phase of the combined zero-phase current data I0S is within the operating region.

  When it is determined that the phase difference between the combined zero-phase current data I0S and the α current data IαSA using the A phase as a reference phase is within the range of the operation region (Yes in step S202), the failure phase determination unit 15a Only the determination output OA indicating the one-phase ground fault failure determination is enabled, and the other determination outputs OB, OC, OBC, OCA, OAB are disabled (step S203).

  On the other hand, when it is determined that the β current data IβSA using the A phase as a reference phase is equal to or greater than a predetermined threshold value ε2 (No in step S201), the failure phase determination unit 15a has the reverse phase of the combined zero phase current data I0S. It is determined whether or not the phase difference between the current data and the α current data IαSA with the A phase as the reference phase is within the range of the operation region (step S204). That is, it is determined whether or not the α current data IαSA calculated using the A phase as the reference phase with respect to the current in the opposite phase of the combined zero phase current data I0S is within the operating region.

  When it is determined that the phase difference between the reverse phase data of the combined zero-phase current data I0S and the α current data IαSA with the A phase as the reference phase is within the operating range (step S204, Yes), the fault phase determination unit 15a enables only the determination output OBC indicating the BC-phase two-phase ground fault determination, and disables the other determination outputs OA, OB, OC, OCA, and OAB (step S205).

  When it is determined that the phase difference between the reverse phase data of the combined zero-phase current data I0S and the α current data IαSA using the A phase as the reference phase is not within the operating range (step S204, No), or the combined zero When it is determined that the phase difference between the phase current data I0S and the α current data IαSA using the A phase as a reference phase is not within the range of the operation region (No in step S202), the failure phase determination unit 15a uses the B phase as a reference. It is determined whether or not the β current data IβSB as a phase is smaller than a predetermined threshold value ε2 (step S206). When it is determined that the β current data IβSB with the B phase as the reference phase is smaller than the predetermined threshold value ε2 (Yes in step S206), the failure phase determination unit 15a uses the combined zero phase current data I0S and the B phase as the reference phase. It is determined whether or not the phase difference from the α current data IαSB is within the range of the operating region (step S207). That is, it is determined whether or not the α current calculated in the reference phase of the α current with the B phase as the reference phase is within the operating range with respect to the current phase of the combined zero-phase current data I0S.

  When it is determined that the phase difference between the combined zero-phase current data I0S and the α current data IαSB using the B phase as a reference phase is within the operating region (Yes in step S207), the failure phase determination unit 15a Only the determination output OB indicating the one-phase ground fault failure determination is enabled, and the other determination outputs OA, OC, OBC, OCA, OAB are disabled (step S208).

  On the other hand, when it is determined that the β current data IβSB using the B phase as a reference phase is equal to or greater than a predetermined threshold ε2 (No in step S206), the failure phase determination unit 15a has the opposite phase of the combined zero phase current data I0S. It is determined whether or not the phase difference between the current data and the α current data IαSB with the B phase as the reference phase is within the operating region (step S209). That is, it is determined whether or not the α current data IαSB calculated using the B phase as the reference phase with respect to the current in the opposite phase of the combined zero phase current data I0S is within the range of the operation region.

  When it is determined that the phase difference between the reverse phase data of the combined zero-phase current data I0S and the α current data IαSB with the B phase as the reference phase is within the range of the operation region (Yes in step S209), the fault phase determination unit 15a enables only the determination output OCA indicating the CA phase two-phase ground fault determination, and disables the other determination outputs OA, OB, OC, OBC, OAB (step S210).

  When it is determined that the phase difference between the reverse phase data of the combined zero phase current data I0S and the α current data IαSB with the B phase as the reference phase is not within the range of the operating region (No in step S209), or the combined zero When it is determined that the phase difference between the phase current data I0S and the α current data IαSB using the B phase as a reference phase is not within the range of the operation region (No in step S207), the failure phase determination unit 15a uses the C phase as a reference. It is determined whether or not the β current data IβSC as a phase is smaller than a predetermined threshold value ε2 (step S211). When it is determined that the β current data IβSC with the C phase as the reference phase is smaller than the predetermined threshold value ε2 (Yes in step S211), the failure phase determination unit 15a uses the combined zero phase current data I0S and the C phase as the reference phase. It is determined whether or not the phase difference from the α current data IαSC is within the range of the operation region (step S212). That is, it is determined whether or not the α current calculated in the reference phase of the α current with the C phase as the reference phase with respect to the current phase of the combined zero-phase current data I0S is within the operating region.

  When it is determined that the phase difference between the combined zero-phase current data I0S and the α current data IαSC with the C phase as a reference phase is within the range of the operation region (Yes in step S212), the failure phase determination unit 15a Only the judgment output OC indicating the one-phase ground fault failure judgment is validated, and the other judgment outputs OA, OB, OBC, OCA, OAB are invalidated (step S213).

  On the other hand, when it is determined that the β current data IβSC with the C phase as the reference phase is equal to or greater than the predetermined threshold value ε2 (No in step S211), the failure phase determination unit 15a determines the reverse phase of the combined zero phase current data I0S. It is determined whether or not the phase difference between the current data and the α current data IαSC using the C phase as a reference phase is within the operating region (step S214). That is, it is determined whether or not the α current data IαSC calculated using the C phase as the reference phase with respect to the current in the opposite phase of the combined zero phase current data I0S is within the operating region.

  When it is determined that the phase difference between the reverse phase data of the combined zero-phase current data I0S and the α current data IαSC with the C phase as the reference phase is within the operating range (step S214, Yes), the fault phase determination unit 15a enables only the determination output OAB indicating the AB phase two-phase ground fault determination, and disables the other determination outputs OA, OB, OC, OBC, OCA (step S215).

  On the other hand, when it is determined that the phase difference between the reverse phase data of the combined zero phase current data I0S and the α current data IαSC using the C phase as the reference phase is not within the operating range (step S214, No), When it is determined that the phase difference between the phase current data I0S and the α current data IαSC with the C phase as the reference phase is not within the range of the operation region (No in step S212), or the combined zero phase current data I0S is the threshold value ε1 In the following case (step S200, No), the failure phase determination unit 15a determines that no failure has occurred on the power transmission line 1, and determines all the determination outputs OA, OB, OC, OBC, OCA, OAB. Is invalidated (step S216).

  As described above, the failure phase determination unit 15a determines that the β current data IβS having the A phase, the B phase, or the C phase as the reference phase is equal to or less than the threshold ε2 when the combined zero-phase current data I0S is equal to or greater than the threshold ε1. When the phase difference between the α current data IαS with the phase as the reference phase and the combined zero-phase current data I0S is within the operating range (when the α current data IαS with the phase as the reference phase is close to the same phase) Is determined that the phase is a fault phase in a one-phase ground fault, and β current data IβS with A phase, B phase, or C phase as a reference phase is larger than threshold ε2 and the phase is set as a reference If the phase difference between the α current data IαS and the reverse phase of the combined zero-phase current data I0S is within the operating range (if the α current data IαS with the phase as the reference phase is close to the reverse phase) It is determined that the phase is a healthy phase in 2 ground faults. It is determined that the fault phase 2 phase. The operation region is set to a value such that any one of the reference phases of the A phase, the B phase, and the C phase falls within the operation region.

  Next, the correctness of the operation of the above-described zero-phase current differential relay 3a will be described with reference to FIGS. FIG. 8 shows an equivalent circuit in the Clarke coordinate method in the case of a phase A single-phase ground fault (A-phase ground fault). FIG. 9 shows an equivalent circuit in the Clarke coordinate method in the case of a BC-phase two-phase ground fault (BC-phase ground fault). As shown in FIG. 8, in the case of the A-phase ground fault, no current flows in the β current Iβ, and almost the same phase current flows in the α current data Iα and the current data I0. On the other hand, as shown in FIG. 9, in the case of a BC phase ground fault, a current flows through the β current data Iβ, and the α current data Iα and the current data I0 are almost in opposite phases. When the power line internal failure occurs when the power supply phases at both ends are substantially equal, the phases of α current data Iα, β current data Iβ, and current data I0 at both ends are substantially equal. Therefore, in the case of an A-phase ground fault with respect to the combined current at both ends, no current flows in the β current data Iβ, and almost the same phase current flows in the α current data Iα and the current data I0. On the other hand, in the case of a BC-phase ground fault, a condition is satisfied that a current flows in the β current data Iβ, and the α current data Iα and the current data I0 are substantially in opposite phases.

  As described above, in the second embodiment, the zero-phase current of the self-end side three-phase current obtained from the self-end current transformer and the counter-end side three-phase current obtained from the counterpart current transformer are calculated. When a ground fault in the power line transmission line is detected based on the differential calculation result based on the zero-phase current, the zero-phase current of the self-side three-phase current and the zero-phase current of the counterpart three-phase current And the combined current of each phase obtained by synthesizing the combined zero-phase current and the same-phase current of the own-end side three-phase current and the opposite-end side three-phase current (the same phase between the own end and the opposite end) The ground fault that has occurred on the power transmission line based on the α current for each phase based on the vector sum current) and the β current for each phase based on the combined current is a one-phase ground fault. Whether or not the failure current on the end side is small, as in the conventional failure phase determination Without using voltage input, it is possible to reliably determine whether or not the ground fault that has occurred in the power transmission line is a one-phase ground fault, and determine the fault phase. In the second embodiment, since the β current is near zero and the reference phase of the α current that substantially matches the phase of the zero phase current is determined as the failure phase of the one-phase ground fault. Even if the fault current on the own end side is extremely small without using the voltage input as in the conventional fault phase determination, the fault phase on the power transmission line can be reliably detected.

  In the determination processing operation of the failure determination processing unit described with reference to the flowchart of FIG. 7, the combined zero-phase current data I0S and the predetermined threshold value ε1 are compared. Instead of comparing the data I0S with the predetermined threshold value ε1, it may be determined whether the zero-phase current differential relay element output, which is the output of the zero-phase current differential relay element unit 14, is valid or invalid. . In this case, the case where “the zero-phase current differential relay element output is valid” corresponds to the case where “the combined zero-phase current data I0S is greater than the threshold ε1”, and “the zero-phase current differential relay element output is invalid”. This corresponds to the case where “the combined zero-phase current data I0S is equal to or less than the threshold value ε1”.

Embodiment 3 FIG.
A third embodiment of the present invention will be described with reference to FIGS. 10 and 11. In the second embodiment, the ground fault on the power transmission line 1 using the α current data IαS with each phase as the reference phase, the β current data IβS with each phase as the reference phase, and the combined zero-phase current I0S. The presence or absence of failure and its failure phase were identified. In the third embodiment, the β current data IβS having each phase as the reference phase and the combined zero-phase current I0S are used on the power transmission line 1 without using the α current data IαS having each phase as the reference phase. The presence / absence of a ground fault and the failure phase are identified.

  The configuration of the power system to which the zero-phase current differential relay of the third embodiment is applied is the same as that of the power system of the first embodiment shown in FIG. Instead of -1 and 3-2, zero-phase current differential relays 3b-1 and 3b-2 are used.

  FIG. 10 is a block diagram showing a configuration of a zero-phase current differential relay 3b (shown by 3b-1 and 3b-2) according to the third embodiment. In the zero-phase current differential relay 3b of the third embodiment shown in FIG. 10, the α current calculation unit 18 is deleted from the zero-phase current differential relay 3a of the second embodiment shown in FIG. A fault phase determination unit 15b is provided instead of the phase determination unit 15a. Components having the same functions as those of the zero-phase current differential relay 3a of the second embodiment shown in FIG. 6 are given the same reference numerals, and redundant descriptions are omitted.

  The failure phase determination unit 15b is based on the β current data IβS for each phase input from the β current calculation unit 19 and the combined zero phase current data I0S input from the both-end zero phase combining unit 13. 1 is determined whether or not a failure has occurred. The failure phase determination unit 15b enables the determination output OA and disables the other determination outputs OB, OC, OBC, OCA, and OAB when determining that it is the A-phase one-phase ground fault. The failure phase determination unit 15b enables the determination output OB and disables the other determination outputs OA, OC, OBC, OCA, and OAB when determining that it is a B-phase one-phase ground fault. The failure phase determination unit 15b validates the decision output OC and invalidates the other decision outputs OA, OB, OBC, OCA, and OAB when it is determined that a C-phase one-phase ground fault has occurred.

  If the failure phase determination unit 15b determines that a two-phase ground fault has occurred in the BC phase, the failure phase determination unit 15b enables the determination output OBC and disables the other determination outputs OA, OB, OC, OCA, and OAB. If the failure phase determination unit 15b determines that a CA phase two-phase ground fault has occurred, the failure phase determination unit 15b enables the determination output OCA and disables the other determination outputs OA, OB, OC, OBC, and OAB. If the failure phase determination unit 15b determines that the AB phase two-phase ground fault has occurred, the failure phase determination unit 15b enables the determination output OAB and disables the other determination outputs OA, OB, OC, OBC, and OCA.

  Next, the operation of the zero-phase current differential relay 3b according to the third embodiment will be described. The difference between the zero-phase current differential relay 3b of the third embodiment and the zero-phase current differential relay 3a of the second embodiment is that the zero-phase current differential relay 3a of the second embodiment is different. Using the α current data IαS with each phase as the reference phase, the β current data IβS with each phase as the reference phase, and the combined zero-phase current I0S, the presence / absence of a failure on the power transmission line 1 and its failure phase are determined. In contrast, the third embodiment uses the β current data IβS having each phase as the reference phase and the combined zero-phase current I0S without using the α current data IαS having each phase as the reference phase. This is to specify whether or not a failure has occurred on the power transmission line 1 and its failure phase, and the other operations are the same as those of the zero-phase current differential relay 3a of the second embodiment. Then, the failure phase determination that performs the failure phase determination process that is the difference Only the operation of the unit 15b will be described.

  The operation of fault phase determination unit 15b of zero-phase current differential relay 3b according to the third embodiment of the present invention will be described with reference to the flowchart of FIG. The failure phase determination unit 15b determines whether or not the combined zero-phase current data I0S is greater than a predetermined threshold value ε1 (step S300). Here, the threshold value ε1 is a value indicating a sensitivity equivalent to the zero-phase difference current relay element sensitivity of the zero-phase current differential relay element unit 14, or is equal to or greater than the zero-phase difference current relay element sensitivity of the zero-phase current differential relay element unit 14. To do.

  If the combined zero-phase current data I0S is equal to or less than the threshold value ε1 (step 300, No), the failure phase determination unit 15b determines that no failure has occurred on the power transmission line 1, and determines all the determination outputs OA, OB, OC, OBC, OCA, and OAB are invalidated (step S301). If the combined zero-phase current data I0S is larger than the threshold value ε1 (step 300, Yes), whether or not a one-phase ground fault has occurred in the A phase, that is, β current data IβSA using the A phase as a reference phase is determined in advance. It is determined whether or not both the β current data IβSB having the B phase as the reference phase and the β current data IβSC having the C phase as the reference phase are larger than a predetermined threshold ε3, both being smaller than the threshold value ε2 set (step S302). ). The values of the threshold values ε2 and ε3 will be described later.

  When the β current data IβSA with the A phase as the reference phase is smaller than the threshold ε2, and the β current data IβSB with the B phase as the reference phase and the β current data IβSC with the C phase as the reference phase are both greater than the threshold ε3 (step S302, Yes), the failure phase determination unit 15b determines that a one-phase ground fault has occurred in the A phase, validates only the determination output OA indicating the A phase one-phase ground fault determination, The determination outputs OB, OC, OBC, OCA, OAB are invalidated (step S303).

  Β current data IβSA with A phase as a reference phase is equal to or greater than a predetermined threshold value ε2, or at least one of β current data IβSB with B phase as a reference phase and β current data IβSC with C phase as a reference phase If one is less than or equal to the threshold value ε3 (step S302, No), the failure phase determination unit 15b determines whether or not a one-phase ground fault has occurred in the B phase, that is, β current data IβSB with the B phase as the reference phase is the threshold value. It is determined whether or not both β current data IβSA smaller than ε2 and β-phase current data IβSA with phase A as the reference phase and β-current data IβSC with phase C as the reference phase are larger than threshold ε3 (step S304).

  When the β current data IβSB with the B phase as the reference phase is smaller than the threshold ε2, and the β current data IβSA with the A phase as the reference phase and the β current data IβSC with the C phase as the reference phase are both greater than the threshold ε3 (step S304, Yes), the failure phase determination unit 15b determines that a one-phase ground fault has occurred in the B phase, enables only the determination output OB indicating the B phase one-phase ground fault determination, The determination outputs OA, OC, OBC, OCA, OAB are invalidated (step S305).

  When the β current data IβSB with the B phase as the reference phase is greater than or equal to a predetermined threshold ε2, or at least one of the β current data IβSA with the A phase as the reference phase and the β current data IβSC with the C phase as the reference phase If one is less than or equal to the threshold value ε3 (No in step S304), the failure phase determination unit 15b determines whether or not a one-phase ground fault has occurred in the C phase, that is, β current data IβSC with the C phase as the reference phase is the threshold value. It is determined whether or not both β current data IβSA smaller than ε2 and β phase data IβSA using A phase as a reference phase and β current data IβSB using B phase as a reference phase are larger than threshold ε3 (step S306).

  When the β current data IβSC with the C phase as the reference phase is smaller than the threshold ε2, and the β current data IβSA with the A phase as the reference phase and the β current data IβSB with the B phase as the reference phase are both greater than the threshold ε3 (step S306, Yes), the failure phase determination unit 15b determines that a single-phase ground fault has occurred in the C phase, enables only the determination output OC indicating the single-phase ground fault determination in the C phase, The determination outputs OA, OB, OBC, OCA, OAB are invalidated (step S307).

  Β current data IβSC with phase C as a reference phase is equal to or greater than a predetermined threshold value ε2, or at least one of β current data IβSA with phase A as a reference phase and β current data IβSB with phase B as a reference phase If one of them is equal to or less than the threshold value ε3 (No in step S306), the failure phase determination unit 15b uses β current data IβSA with the A phase as the reference phase, β current data IβSB with the B phase as the reference phase, and C phase as the reference phase. It is determined whether or not the maximum value in the β current data IβSC is β current data IβSA based on the A phase (step S308).

  The β current data IβSA with the A phase as the reference phase, the β current data IβSB with the B phase as the reference phase, and the β current data IβSC with the C phase as the reference phase have the maximum value as the β current based on the A phase When it determines with it being data I (beta) SA (step S308, Yes), the failure phase determination part 15b determines with the A phase being a healthy phase, and having detected the two-phase ground fault in BC phase, and the two-phase ground of BC phase Only the judgment output OBC indicating the fault determination is validated, and the other judgment outputs OA, OB, OC, OCA, OAB are invalidated (step S309).

  The β current data IβSA with the A phase as the reference phase, the β current data IβSB with the B phase as the reference phase, and the β current data IβSC with the C phase as the reference phase have the maximum value as the β current based on the A phase When it is determined that the data is not the data IβSA (No in step S308), the failure phase determination unit 15b determines the β current data IβSA with the A phase as the reference phase, the β current data IβSB with the B phase as the reference phase, and the C phase. It is determined whether or not the maximum value in the β current data IβSC as the reference phase is β current data IβSB based on the B phase (step S310).

  Β current data IβSA with phase A as the reference phase, β current data IβSB with phase B as the reference phase, and β current data IβSC with phase C as the reference phase have a maximum value of β current with reference to phase B When it determines with it being data I (beta) SB (step S310, Yes), the failure phase determination part 15b determines that the B phase is a healthy phase and the two-phase ground fault has occurred in the CA phase, and the two phases of the CA phase Only the determination output OCA indicating the fault determination is enabled, and the other determination outputs OA, OB, OC, OBC, OAB are disabled (step S311).

  Β current data IβSA with phase A as the reference phase, β current data IβSB with phase B as the reference phase, and β current data IβSC with phase C as the reference phase have a maximum value of β current with reference to phase B When it is determined that the data is not IβSB (No in step S310), that is, β current data IβSA with the phase as the reference phase, β current data IβSB with the B phase as the reference phase, and β current data with the C phase as the reference phase When it is determined that the maximum value in IβSC is β current data IβSC based on the C phase, the failure phase determination unit 15b indicates that the C phase is a healthy phase and a two-phase ground fault has occurred in the AB phase. Only the determination output OAB indicating the AB phase two-phase ground fault determination is validated, and the other judgment outputs OA, OB, OC, OBC, OCA are invalidated (step S312).

Next, the justification of the failure determination process of the failure phase determination unit 15b described above will be described. First, the case of the A-phase one-phase ground fault (A-phase ground fault) will be described. In the case of an A-phase ground fault, a fault current flows in the A-phase current IA input to the zero-phase current differential relay 3b, and a load current flows in the B-phase and C-phase current IB and IC. Flowing. Since the combined current at both ends is taken, only the fault current remains in the combined current when passing through at both ends, such as the load current, and the following (Equation 13) and ((Equation 14) hold.
IAS = If (Formula 13)
IBS = ICS = 0 (Formula 14)
Note that IAS is A-phase combined current data, IBS is B-phase combined current data, ICS is C-phase combined current data, and If is the sum of fault currents at both ends.

That is, according to the above (Expression 10) to (Expression 12), (Expression 13), and (Expression 14), the β current data IβSA with the A phase as the reference phase, the β current data IβSB with the B phase as the reference phase, and the C phase Β current data IβSC with reference phase as
IβSA = (IBS-ICS) × (√3 / 3) = 0
IβSB = (ICS−IAS) × (√3 / 3) = − If (√3 / 3)
IβSC = (IAS−IBS) × (√3 / 3) = If (√3 / 3)
Thus, the β current data IβS with the failure phase as the reference phase is “0”, and the failure current flows in the healthy phase of the β current. Therefore, three conditions of “IβSA <ε2”, “IβSB> ε3”, and “IβSC> ε3” are satisfied. Here, the threshold value ε3 is a value that can be detected by a current at which the zero-phase current differential relay element output operates (becomes valid) due to an internal failure of the power transmission line 1. The threshold value ε2 is a value that does not cause erroneous detection due to an error of the current transformer, and is a value that can be clearly distinguished from a value smaller than the threshold value ε3.

In addition, three conditions of “IβSA <ε2”, “IβSB> ε3”, “IβSC> ε3”, “IβSB <ε2”, “IβSA> ε3”, “IβSC> ε3”, which are the conditions of the one-phase ground fault. If any of the three conditions “IβSC <ε2”, “IβSA> ε3”, and “IβSB> ε3” is not satisfied, a two-phase ground fault occurs. For example, in the case of a BC-phase two-phase ground fault (BC-phase ground fault), a load current flows through the A-phase self-current IA, and the B-phase and C-phase self-currents IB and IC Fault current flows. Since the combined current at both ends is taken, only the fault current remains in the combined current when passing through at both ends, such as the load current, and the following (Equation 15) holds.
IAS = 0 (Formula 15)
Note that IAS is A-phase combined current data. From (Equation 10) to (Equation 12) and (Equation 15), if the current data of the current flowing between the B phase and the C phase is IBCS, the β current data IβSA with the A phase as the reference phase and the B phase as the reference phase Β current data IβSB and β current data IβSC with the C phase as a reference phase are
IβSA = (IBS-ICS) × (√3 / 3) = IBCS (√3 / 3)
IβSB = (ICS−IAS) × (√3 / 3) = ICS (√3 / 3)
IβSC = (IAS−IBS) × (√3 / 3) = − IBS (√3 / 3)
Here, since the relation of “effective value of IBCS> effective value of IBS = effective value of ICS” is established, β current data IβA with the A phase as the reference phase and β current data IβB, C with the B phase as the reference phase For the three current data of β current data IβC with the phase as the reference phase, the reference phase indicating the maximum current data is a healthy phase of the two-phase ground fault. Thus, the failure phase determination process can be executed by determining the effective value of the β current data IβS for each phase.

  As described above, in the third embodiment, the zero-phase current of the self-end three-phase current obtained from the self-current transformer and the counterpart three-phase current obtained from the counterpart current transformer When a ground fault in the power line transmission line is detected based on the differential calculation result based on the zero-phase current, the zero-phase current of the self-side three-phase current and the zero-phase current of the counterpart three-phase current And the combined current of each phase obtained by synthesizing the combined zero-phase current and the same-phase current of the own-end side three-phase current and the opposite-end side three-phase current (the same phase between the own end and the opposite end) Based on the β current for each phase based on the vector sum current), it is determined whether the ground fault occurring on the power transmission line is a one-phase ground fault and determining the fault phase. Therefore, even if the local fault current is small, voltage input is not used as in the conventional fault phase determination. Ground fault occurring in the power transmission line can be reliably fault phase determination and isolation of whether or not disabled 1 Aichi 絡故. In the third embodiment, the failure phase of the one-phase ground fault is determined based on the level of the effective value of the β current for each phase, and the two-phase ground fault is determined based on the maximum value of the β current for each phase. Since the fault phase is determined, the fault phase on the power transmission line can be ensured without using voltage input as in the conventional fault phase determination even when the fault current on the local end side is extremely small. Can be detected. Further, by using the Clarke coordinates, the phase shift calculation necessary for the calculation of the positive phase current and the negative phase current of the symmetric coordinates becomes unnecessary, and the processing can be simplified.

  In the determination processing operation of the failure determination processing unit described with reference to the flowchart of FIG. 11, the composite zero-phase current data I0S and the predetermined threshold value ε1 are compared. Instead of comparing the data I0S with the predetermined threshold value ε1, it may be determined whether the zero-phase current differential relay element output, which is the output of the zero-phase current differential relay element unit 14, is valid or invalid. . In this case, the case where “the zero-phase current differential relay element output is valid” corresponds to the case where “the combined zero-phase current data I0S is greater than the threshold ε1”, and “the zero-phase current differential relay element output is invalid”. This corresponds to the case where “the combined zero-phase current data I0S is equal to or less than the threshold value ε”.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described with reference to FIGS. In the previous first to third embodiments, the presence / absence of the occurrence of the one-phase ground fault or the two-phase ground fault on the power transmission line 1 and the phase in which the fault occurred are specified. In the fourth embodiment, Whether or not a one-phase ground fault or two-phase ground fault has occurred on the power transmission line 1 and only the phase in which the one-phase ground fault has occurred are specified.

  The configuration of the power system to which the zero-phase current differential relay of the fourth embodiment is applied is the same as that of the power system of the first embodiment shown in FIG. Instead of -1 and 3-2, zero-phase current differential relays 3c-1 and 3c-2 are used.

  FIG. 12 is a block diagram showing a configuration of a zero-phase current differential relay 3c (shown by 3c-1 and 3c-2) according to the fourth embodiment. In the zero-phase current differential relay 3c of the fourth embodiment shown in FIG. 12, the AND circuits 16BC, 16CA, and 16AB are deleted from the zero-phase current differential relay 3b of the third embodiment shown in FIG. The AND circuit 163 is added, and a failure phase determination unit 15c is provided instead of the failure phase determination unit 15b. Components having the same functions as those of the zero-phase current differential relay 3b according to the third embodiment shown in FIG. 10 are given the same reference numerals, and redundant descriptions are omitted.

  The failure phase determination unit 15c is based on the β current data IβS for each phase input from the β current calculation unit 19 and the combined zero phase current data I0S input from the both-end zero phase combining unit 13. 1 is determined whether or not a failure has occurred. The failure phase determination unit 15c enables the determination output OA and disables the other determination outputs OB, OC, and O3Φ when determining that the A-phase one-phase ground fault has occurred. The failure phase determination unit 15c enables the determination output OB and disables the other determination outputs OA, OC, and O3Φ when determining that the B-phase one-phase ground fault has occurred. The failure phase determination unit 15c enables the determination output OC and disables the other determination outputs OA, OB, and O3Φ when determining that the C-phase one-phase ground fault has occurred. If the failure phase determination unit 15c determines that a failure other than the one-phase ground fault has occurred, the failure phase determination unit 15c enables the determination output O3Φ and disables the other determination outputs OA, OB, and OC.

  The AND circuit 163 performs a three-phase operation on a logical product of the determination output O3Φ indicating the three-phase operation input from the failure phase determination unit 15c and the zero-phase current element output input from the zero-phase current differential relay element unit 14. The determination result is output as 3ΦT.

  Next, the difference between the zero-phase current differential relay 3c of the fourth embodiment of the present invention and the zero-phase current differential relay 3b of the third embodiment is that the zero-phase current of the third embodiment is the same. Whereas the differential relay 3b specifies the fault phase in the two-phase ground fault, the zero-phase current differential relay 3c of the fourth embodiment does not specify the fault phase in the two-phase ground fault. This is to output the presence / absence of a three-phase operation, and the other operations are the same as those of the zero-phase current differential relay 3b of the third embodiment. Only the operation of the failure phase determination unit 15c will be described.

  With reference to the flowchart of FIG. 13, the operation of failure phase determination unit 15c of zero-phase current differential relay 3c according to the fourth embodiment of the present invention will be described. The failure phase determination unit 15c determines whether or not the combined zero-phase current data I0S is larger than a predetermined threshold value ε1 (step S400), and when the combined zero-phase current data I0S is equal to or less than the threshold value ε1 (No in step S400). The failure phase determination unit 15c determines that no failure has occurred on the power transmission line 1, and invalidates all the determination outputs OA, OB, OC, and O3Φ (step S401).

  When the combined zero-phase current data I0S is larger than the threshold ε1 (step 400, Yes), the failure phase determination unit 15c determines that the β current data IβSA with the A phase as the reference phase is smaller than the predetermined threshold ε2 and the B phase. It is determined whether or not both the β current data IβSB having the reference phase as the reference phase and the β current data IβSC having the C phase as the reference phase are larger than a predetermined threshold value ε3 (step S402). If the current data IβSA is smaller than the threshold value ε2, and both the β current data IβSB with the B phase as the reference phase and the β current data IβSC with the C phase as the reference phase are larger than the threshold ε3 (Yes in step S402), the failure phase determination The unit 15c determines that a single-phase ground fault has occurred in the A phase, validates only the determination output OA indicating the single-phase ground fault failure determination of the A phase, and outputs other determination outputs O. B, OC, and O3Φ are invalidated (step S403).

  Β current data IβSA with A phase as a reference phase is equal to or greater than a predetermined threshold value ε2, or at least one of β current data IβSB with B phase as a reference phase and β current data IβSC with C phase as a reference phase Is equal to or less than the threshold ε3 (No in step S402), the failure phase determination unit 15c determines that the β current data IβSB having the B phase as the reference phase is smaller than the threshold ε2 and the β current data IβSA having the A phase as the reference phase and It is determined whether or not both β current data IβSC with phase C as the reference phase is larger than threshold value ε3 (step S404), β current data IβSB with phase B as the reference phase is smaller than threshold value ε2 and A phase is the reference. When both the β current data IβSA having the phase C and the β current data IβSC having the C phase as the reference phase are larger than the threshold value ε3 (Yes in step S404), the failure phase determination unit 15 Determines that a one-phase ground fault has occurred in the B phase, enables only the judgment output OB indicating the one-phase ground fault fault judgment of the B phase, and invalidates the other judgment outputs OA, OC, and O3Φ. (Step S405).

  When the β current data IβSB with the B phase as the reference phase is greater than or equal to a predetermined threshold ε2, or at least one of the β current data IβSA with the A phase as the reference phase and the β current data IβSC with the C phase as the reference phase Is equal to or less than the threshold ε3 (No in step S404), the failure phase determination unit 15c determines that the β current data IβSC having the C phase as the reference phase is smaller than the threshold ε2 and the β current data IβSA having the A phase as the reference phase It is determined whether or not both the β current data IβSB with the B phase as the reference phase is larger than the threshold ε3 (step S406), the β current data IβSC with the C phase as the reference phase is smaller than the threshold ε2 and the A phase is the reference If both the β current data IβSA for the phase and the β current data IβSB for the B phase as the reference phase are larger than the threshold value ε3 (Yes in step S406), the failure phase determination unit 15 Determines that a single-phase ground fault has occurred in the C phase, enables only the judgment output OC indicating the single-phase ground fault judgment of the C phase, and invalidates the other judgment outputs OA, OB, and O3Φ. (Step S407).

  Β current data IβSC with phase C as a reference phase is equal to or greater than a predetermined threshold value ε2, or at least one of β current data IβSA with phase A as a reference phase and β current data IβSB with phase B as a reference phase If the threshold is ε3 or less (step S406, No), the failure phase determination unit 15c determines that a failure other than the one-phase ground fault has occurred, enables the determination output O3Φ indicating the three-phase operation, and others. The determination outputs OA, OB, OC are invalidated (step S408).

  As described above, the failure phase determination unit 15c omits the two-phase ground fault determination process of the failure phase determination unit 15b of the third embodiment, and the combined zero-phase current data I0S is larger than the threshold ε1. It is determined that a failure has not occurred in the power transmission line 1, and if the failure that has occurred is not any one of the A-phase, B-phase, and C-phase one-phase ground faults, the failure phase is identified It outputs only that a failure has occurred.

  As described above, in the fourth embodiment, the zero-phase current of the self-side three-phase current obtained from the self-current transformer and the counterpart three-phase current obtained from the counterpart current transformer When a ground fault in the power line transmission line is detected based on the differential calculation result based on the zero-phase current, the zero-phase current of the self-side three-phase current and the zero-phase current of the counterpart three-phase current And the combined current of each phase obtained by synthesizing the combined zero-phase current and the same-phase current of the own-end side three-phase current and the opposite-end side three-phase current (the same phase between the own end and the opposite end) Based on the β current for each phase based on the vector sum current), it is determined whether the ground fault occurring on the power transmission line is a one-phase ground fault and determining the fault phase. Therefore, even if the local fault current is small, voltage input is not used as in the conventional fault phase determination. Ground fault occurring in the power transmission line can be reliably fault phase determination and isolation of whether or not disabled 1 Aichi 絡故. In the fourth embodiment, since the fault phase of the one-phase ground fault is determined based on the effective value level of the β current for each phase, voltage input is performed as in the conventional fault phase determination. Without using, even if the fault current on the end side is extremely small, the fault phase on the power transmission line can be reliably detected.

  In addition, in the case of a one-phase ground fault, each phase operation is performed with a fault phase specified. In the case of a two-phase ground fault, a three-phase operation is performed without specifying a fault phase. Only the effective value level of the phase is determined, and the processing can be simplified.

  In the determination processing operation of the failure determination processing unit described with reference to the flowchart of FIG. 13, the combined zero-phase current data I0S and the predetermined threshold value ε1 are compared. Instead of comparing the data I0S with the predetermined threshold value ε1, it may be determined whether the zero-phase current differential relay element output, which is the output of the zero-phase current differential relay element unit 14, is valid or invalid. . In this case, the case where “the zero-phase current differential relay element output is valid” corresponds to the case where “the composite zero-phase current data I0S is greater than the threshold value ε1”, and “the zero-phase current differential relay element output is invalid”. The case corresponds to the case where “the combined zero-phase current data I0S is equal to or less than the threshold ε”.

  As described above, the zero-phase current differential relay according to the present invention is useful as an invention for cutting off only the faulty phase when a power transmission line fails.

It is a figure which shows the structure of the system for electric power to which the zero phase current differential relay in this invention is applied. FIG. 3 is a block diagram illustrating a configuration of a zero-phase current differential relay according to the first embodiment. 3 is a flowchart for explaining an operation of a fault phase determination unit of the zero-phase current differential relay of the first embodiment. It is a figure which shows the equivalent circuit by the symmetrical coordinate method in the case of A phase ground fault. It is a figure which shows the equivalent circuit by the symmetrical coordinate method in the case of BC phase ground fault. FIG. 6 is a block diagram illustrating a configuration of a zero-phase current differential relay according to a second embodiment. 6 is a flowchart for explaining an operation of a fault phase determination unit of the zero-phase current differential relay of the second embodiment. It is a figure which shows the equivalent circuit by the Clarke coordinate method in the case of A phase ground fault. It is a figure which shows the equivalent circuit by the Clarke coordinate method in the case of BC phase ground fault. FIG. 6 is a block diagram illustrating a configuration of a zero-phase current differential relay according to a third embodiment. 10 is a flowchart for explaining an operation of a fault phase determination unit of the zero-phase current differential relay of the third embodiment. FIG. 6 is a block diagram illustrating a configuration of a zero-phase current differential relay according to a fourth embodiment. 10 is a flowchart for explaining an operation of a fault phase determination unit of the zero-phase current differential relay of the fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power transmission line 2-1 and 2-2 Current transformer 3, 3a, 3b, 3c Zero phase current differential relay 4A, 4B, 4C Input current conversion part 5 Reception part 6A, 6B, 6C Reception current conversion part 7 Current time synchronization unit 8A, 8B, 8C Combining unit 9 Self-end zero-phase combining unit 10 Counter-end zero-phase combining unit 11 Positive-phase combining unit 12 Reverse-phase combining unit 13 Zero-phase combining unit 14 Zero-phase current differential relay element unit 15, 15a, 15b, 15c Failure phase determination unit 16A, 16B, 16C, 16BC, 16CA, 16AB, 163 AND circuit 17 Transmission unit 18 α current calculation unit 19 β current calculation unit

Claims (5)

Based on the differential calculation result based on the zero-phase current of the three-phase current of the self-end obtained from the self-current transformer and the zero-phase current of the three-phase current of the counter end obtained from the current transformer of the counterpart In the zero-phase current differential relay with a determination unit that determines the presence or absence of a ground fault in the power line transmission line,
The determination unit
A positive phase for obtaining a positive phase current using each phase as a reference phase based on a synthesized current for each phase obtained by synthesizing a current of the same phase of the self-end side three-phase current and the counterpart end side three-phase current A synthesis unit;
Reverse phase for obtaining a reverse phase current using each phase as a reference phase based on a combined current for each phase obtained by synthesizing the same phase current of the self-end side three-phase current and the counterpart end side three-phase current A synthesis unit;
Both-ends zero-phase synthesis unit for obtaining a combined zero-phase current by synthesizing the zero-phase current of the self-end side three-phase current and the zero-phase current of the counterpart end-side three-phase current;
With
Based on the positive phase current, the negative phase current, and the combined zero phase current, it is determined whether or not a ground fault that has occurred on the power transmission line is a one-phase ground fault and the fault phase can be determined. Zero phase current differential relay characterized by The determination unit
Based on the combined zero-phase current and the negative-phase current in each phase, it is determined whether the ground fault is a one-phase ground fault,
When it is determined that the ground fault is not a one-phase ground fault, it is determined that the ground fault is a two-phase ground fault due to two phases other than the phase determined not to be the ground fault. The zero-phase current differential relay according to 1. Based on the differential calculation result based on the zero-phase current of the three-phase current of the self-end obtained from the self-current transformer and the zero-phase current of the three-phase current of the counter end obtained from the current transformer of the counterpart In the zero-phase current differential relay with a determination unit that determines the presence or absence of a ground fault in the power line transmission line,
The determination unit
A β current calculation unit for obtaining a β current for each phase based on a combined current of each phase obtained by combining the current of the same phase of the self-end side three-phase current and the counterpart end side three-phase current;
Both-ends zero-phase synthesis unit for obtaining a combined zero-phase current by synthesizing the zero-phase current of the self-end side three-phase current and the zero-phase current of the counterpart end-side three-phase current;
With
Based on the β current and the combined zero-phase current, it is determined whether or not a ground fault that has occurred on the power transmission line is a one-phase ground fault and whether or not a fault phase can be determined. Differential relay. The determination unit determines whether or not the ground fault is a one-phase ground fault based on the level of the β current for each phase.
When it is determined that the ground fault is not a one-phase ground fault, it is determined that the two-phase ground fault is caused by two phases other than the phase having the maximum level in the β current in each phase. The zero-phase current differential relay according to claim 3. The determination unit
An α current calculation unit for obtaining an α current for each phase based on a combined current of each phase obtained by combining the current of the same end side three-phase current and the opposite end side three-phase current;
Further comprising
The determination unit
A first determination process for determining whether the ground fault is a ground fault in the own phase based on the level of the β current;
When it is determined by the first determination process that the ground fault is likely to be a one-phase ground fault, the ground fault is based on the phase difference between the in-phase component of the composite zero-phase current and the α current. A second determination process for determining whether the fault fault is a one-phase ground fault and whether the fault phase can be determined;
When it is determined by the first determination process that the ground fault is not likely to be a single-phase ground fault, based on the phase difference between the current in the opposite phase of the combined zero-phase current and the α current, A third determination process for determining whether or not it is a two-phase ground fault other than the phase determined not to be a one-phase ground fault;
5. The zero-phase current differential relay according to claim 3, wherein each determination process is performed for each phase. 6.

Images