JP2012039734A - Protection relay system of multi-terminal transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protection relay system of a multi-terminal transmission system capable of mounting and operating a ground-fault current differential protection relay and improving stability of the system even in a terminal (slave terminal) that cannot capture a bus voltage.SOLUTION: In a protection relay system of a multi-terminal transmission system including a variable power supply end or a non-power supply end other than a power supply end: a protection relay system of each terminal includes a master device circuit that performs a current differential operation and a slave device circuit that does not perform the curent differential operation and usually selects the master device circuit at the power supply end and the slave device circuit in other terminals; a transmission part of each terminal transmits local end detection information required for the current differential operation of the master device circuit; a transmission part of the power supply end further transmits a bus voltage of the power supply end; a protection relay device of the power supply end operates a local end circuit breaker according to the result of the current differential operation and transmits the result of the current differential operation to other terminals; and slave device circuits of the other terminals operate the local end circuit breaker according to the bus voltage of the power supply end and the result of the current differential operation transmitted from the power supply end side.

Description

  The present invention relates to a protective relay system for a multi-terminal power transmission system, and more particularly, to a protective relay system for a multi-terminal power transmission system that includes variable power supply terminals and non-power supply terminals and performs pause end processing.

  In a multi-terminal power transmission system, a protection relay system that performs idle end processing is known from Patent Document 1.

  In Patent Document 1, a parent device is provided in two or more terminals of each terminal of a power transmission line, each parent device performs failure determination within a protection section, and sends the result to a child device in a so-called transfer interruption format. Protect transmission lines.

  Also, some of the power transmission line terminals may be treated as dormant ends. In this case, even if one parent device is in a dormant state, the other parent device is moving, which hinders overall protection. Absent.

Japanese Patent Laid-Open No. 10-23654

  In recent years, the number of multi-terminal power transmission systems has increased due to the spread of distributed power sources, etc., but some multi-terminal power transmission systems include those that do not have a power supply behind each terminal or are small in size even if they exist There is. This is a so-called variable power supply terminal or non-power supply terminal, and there is a problem that a sufficient fault current cannot be obtained in the case of an internal failure.

  In many cases, a current differential protection relay system is used for protection here, and current information obtained by simultaneous sampling at each end of the multi-terminal is transmitted via the transmission line and used for protection calculation. To do. For example, when the zero-phase current differential method is applied for ground fault protection, calculation is performed using the zero-phase voltage and the zero-phase difference current, so voltage data and current data for all terminals are required. Such an internal failure is often determined by a protective relay device installed at the power supply end, and an operation result is transmitted to the variable power supply end or the non-power supply end to adopt a transfer interruption form.

  However, the zero-phase voltage, which is the input of the zero-phase current differential protection relay mounted on the power supply terminal as the master terminal, generally uses the bus voltage in many cases, but when the bus voltage is used In other words, the child terminals (variable power supply terminals or non-power supply terminals) other than the parent terminal cannot take in voltage.

  Further, since the transmission band for transmission is narrow, only current data and zero-phase voltage data can be transmitted to each terminal. Therefore, the ground fault current differential protection relay of each phase voltage capture method cannot be applied, and the ground fault current differential protection relay can be mounted only at the parent end where the bus voltage is captured.

  In addition, in the ground fault current differential protection relay by taking in the zero phase voltage, since it is possible to transmit the zero phase voltage data, it is possible to provide a ground fault current differential protection relay at each end. There is no idea of providing a ground fault current differential protection relay at each end due to processing capacity, and a ground fault current differential protection relay is provided only at the parent end, as with each phase voltage capture type ground fault current differential protection relay. It wasn't.

  For the above reasons, it is necessary to provide a ground fault current differential protection relay in advance at the parent end to be a representative end.

  As described above, the zero-phase voltage for a ground fault current differential protection relay often uses a bus voltage, and at terminals (child ends) other than the terminal (parent end) that takes in the bus voltage, Can't take in the voltage.

  The object of the present invention is to enable the implementation and calculation of a ground fault current differential protection relay even at a terminal (child end) that cannot take in the bus voltage, and to improve the stability of the system. The purpose is to provide a protective relay system for the grid.

  In the present invention, in a protective relay system of a multi-terminal power transmission system including a variable power supply terminal or a non-power supply terminal in addition to a power supply terminal, the protective relay device of each terminal includes a parent device circuit that performs a current operation calculation and a current differential calculation. In general, the parent device circuit is selected at the power supply terminal, the child device circuit is selected at the other terminals, and the transmission section of each terminal is necessary for the current differential operation of the parent device circuit. Self-end detection information is transmitted, the power-end transmission section further transmits the power-end bus voltage, and the power-end protection relay device operates the self-end breaker with the current differential calculation result of the parent device circuit At the same time, the current differential calculation result is transmitted to the other terminal, and the slave device circuit of the other terminal is determined from the power supply end bus voltage sent from the power supply end side and the current differential calculation result. To operate.

  In addition, the transmission unit of each terminal transmits information that its own terminal is a dormant terminal, and the protection relay device of each terminal uses the information of the dormant terminal to determine the priority order with the power supply terminal being the first. Accordingly, it is determined whether the self-end is the parent device circuit or the child device circuit.

  In addition, the transmission unit of the power supply terminal transmits the power supply bus voltage even when a protective relay device other than the power supply terminal selects the parent device circuit, and the protective relay device of the terminal that selects the parent device circuit Operates the self-end circuit breaker with the current differential calculation result of the parent device circuit and transmits the current differential calculation result to the other terminal, and the child device circuit of the other terminal automatically determines from the current differential calculation result. Operate the end breaker.

In addition, the transmission part of each terminal transmits information including transmission abnormality information,
When the slave device circuit of the other terminal uses the power supply end bus voltage sent from the power supply end side, illegal operation of the protective relay using the power supply end bus voltage is prevented using information on the transmission abnormality.

  According to the apparatus of the present invention, the ground fault current differential protection relay can be mounted and operated even at a terminal (child end) that cannot take in the bus voltage, and the stability of the system can be improved. It is possible.

The figure which shows the protection relay and protection sequence logic with which an arithmetic processing part is provided. The figure which shows an example of the multi-terminal power transmission system to which a protection relay system is applied. The figure which shows a signal transmission system | strain when employ | adopting a current differential protection relay system. The figure which shows the transmission format of the signal transmitted via a signal transmission path. The figure which shows the transmission format of the signal which a power supply end sends out. The figure which shows the transmission format of the signal which terminal terminals other than a power supply terminal send out. Overview of conventional protection system The figure which shows the protection relay system configuration of a representative end. The figure which shows the protection relay system structure of terminals other than a representative end. Overview of conventional protection system

  Examples of the present invention will be described below.

  FIG. 2 shows an example of a multi-terminal power transmission system to which the protective relay system of the present invention is applied. This figure shows an example of a three-terminal configuration in which the A end Ta, the B end Tb, and the C end Tc are connected to the power transmission line L. The A end Ta includes the rear power source 1, but the B end Tb and C The end Tc is a non-power source end 2 or a variable power source end 3. For this reason, the A-terminal Ta includes a bus voltage detector BPD that detects the bus voltage, but the B-terminal Tb and the C-terminal Tc where the rear power supply is not established do not include the bus-voltage detector BPD.

  FIG. 3 shows a signal transmission system when a current differential protection relay system is employed to protect such a multi-terminal power transmission line. In FIG. 3, reference numeral 8 denotes a signal transmission device provided at each terminal, which transmits a signal using the signal transmission path 4 between the terminals Ta, Tb, and Tc. Each terminal includes a protective relay device RY, and the protective relay device RY includes a transmission unit 5 and an arithmetic processing unit 6. Using the above configuration, a current signal detected at each terminal is transmitted through the signal transmission path 4 and a current differential calculation is performed by the arithmetic processing unit 6 to realize a current differential protection relay system. Yes.

FIG. 4 shows a transmission format of a signal transmitted through the signal transmission path 4. However, here, the information used for the protective relay calculation and various displays is mainly described, and the synchronization signal portion and the like are excluded. The main information transmitted in the transmission format is as follows for each frame F1-F7.
F1: Control information such as a pause end F2: Device open / close information such as a self-end circuit breaker, line switch F3: Current differential protection calculation result information (87S for ground fault detection, 87G for short circuit detection)
F4: Ground fault detection signal 51 (ground fault overcurrent relay)
F5: Each terminal current (each phase current, zero phase current)
F6: Each terminal voltage (each phase voltage, zero phase voltage)
F7: Transmission failure information In addition, in realizing the above transmission, the background of the transmission format is that the transmission band of the transmission format has been widened by improving the processing capability of the CPU constituting the protective relay device. In addition to the phase current and zero phase voltage, the zero phase current and each phase voltage could be added. In this example, a digital protection control device using the zero-phase current differential method is described as an example. However, depending on the purpose of protection control, transmission, reactive power, apparent power, and frequency may be added to the transmission format. good.

  FIG. 1 shows a protection relay and protection sequence logic included in the arithmetic processing unit 6 of FIG. The arithmetic processing unit 6 is installed in common at each terminal, but is switched between operating as the circuit of FIG. 7a or operating as the circuit of FIG. The detailed operation will be described with reference to FIG. 7. In short, the output of the AND circuits A3, A4, and A5 is selected in the arithmetic processing unit 6 of the terminal whose own terminal representative signal X is "1", and the negation circuit The output of N1 and N2 is blocked. In the following description, the A terminal Ta will be described as a representative end. Since the own end representative end signal X is “0” at the B end Tb and the C end Tc where the own end is not the representative end, the arithmetic processing unit 6 blocks the outputs of the AND circuits A3, A4, A5. Then, the outputs of the negation circuits N1 and N2 are selected.

  The reason why the A end Ta is the representative end is that the power supply end has a power source behind it, and a more reliable protective relay operation can be expected when the power transmission line fails. As is clear from this result, the A terminal Ta, which is the representative end, executes the protective relay operation as shown in FIG. 7a, and the other B terminal Tb and C terminal Tc execute the protective relay operation as shown in FIG. 7b. . Hereinafter, the protective relay operation of each terminal will be described.

First, the representative end A end Ta will be described. For the transmission line failure determination here, four protective relay operations and one received signal are used. These are as follows.
87S: Current differential protection relay for short circuit detection. The current of all terminals and the bus voltage information of the representative end are input.
87G: Current differential protection relay for ground fault detection. The current of all terminals and the bus voltage information of the representative end are input.
27: Undervoltage relay. The bus voltage at the representative end is used as input.
64: Ground fault overvoltage relay. The bus voltage at the representative end is used as input.
51 Reception: Operation signal of the overcurrent relay 51 at the other end.

  Thus, in order for the representative end to execute the protection relay operation and the protection sequence logic at the representative end, in addition to the information captured at the representative end, information on other terminals obtained via the transmission path 4 ( Current, operation signal of the overcurrent relay 51 at the other end).

  Using these signals, when the AND circuit A4 is finally established, the circuit breaker is tripped at the representative terminal Ta. This is when the OR circuit OR1 is established. There are two conditions for establishing the OR circuit OR1, namely, establishment of the AND circuit A1 and establishment of the AND circuit A2. The former conditions are the occurrence of a short-circuit fault in the transmission line, the short-circuit detection current differential protection relay 87S operation, the undervoltage detection 27 at the representative end, and the overcurrent detection (51 reception) associated with a short-circuit at another terminal. is there. The latter conditions are the occurrence of a ground fault in the transmission line, the operation of the ground fault detection current differential protection relay 87G, and the ground fault overvoltage detection 64 at the representative end.

  The circuit breaker tripping operation at the representative end may be provided with the above-mentioned logic. However, in order to ensure the operation at the other terminals, the representative end uses the AND circuit A3 to detect the short circuit detection current. The operation signal of the differential protection relay 87S is transmitted, and the operation signal of the ground fault detection current differential protection relay 87G is transmitted using the AND circuit A5.

Next, the B end Tb and the C end Tc other than the representative end will be described. In this case, two protective relay operations and two received signals are used for power transmission line failure determination. These are as follows.
51: Overcurrent relay. The current at the end is used as input.
27: Undervoltage relay. The bus voltage at the representative end is used as input.
87S reception: Current differential protection relay operation for short-circuit detection at the representative end.
87G reception: Current differential protection relay operation for ground fault detection at the representative end.

Using these signals, when the negative circuit N2 is finally established, the representative terminal Ta
Circuit breaker tripping of the B terminal Tb and the C terminal Tc other than the above is when the OR circuit OR2 is established. There are two conditions for establishing the OR circuit OR2: the establishment of the AND circuit A6 and the 87G reception (current differential protection relay operation for ground fault detection at the representative end). The former conditions are the occurrence of a short-circuit fault in the transmission line, the 87S reception (current differential protection relay operation for short-circuit detection at the representative end), and the undervoltage relay 27 operation at its own end. As is clear from this, the breaker tripping at the B end Tb and the C end Tc other than the representative end is a so-called transfer interruption upon receiving the determination result of the representative end.

  Here, the operation of the undervoltage relay 27 is confirmed. This is to detect short circuit reliably by matching with 87S reception (current differential protection relay operation for short circuit detection of representative terminal), but at B terminal Tb and C terminal Tc other than representative terminal Ta Since the bus voltage is not detected, the bus voltage information transmitted from the A terminal Ta is used for this confirmation. That is, as shown in FIG. 6, the undervoltage relay 27 is configured to receive information on each phase voltage of the frame F6 in the A-end transmission format of FIG. In addition, the transmission failure detection signal of the frame F7 is input, and the operation of the undervoltage relay 27 is blocked at the time of transmission failure.

  More specifically, the undervoltage relay 27 operates by detecting a voltage drop, and the flip-flop FF is set under a matching condition that does not detect a transmission failure. The undervoltage relay 27 does not operate and the voltage is not lowered. The flip-flop FF is reset under a coincidence condition that does not detect a defect to obtain a final output. With this device, the A-end bus voltage obtained via the transmission line can be used even at the B-end Tb and the C-end Tc where the bus-bar voltage cannot be taken in. As a result, an accident detection judgment using the voltage element is made. Therefore, the device reliability can be improved.

  In addition, when using transmission data, it is necessary to consider abnormality of transmission data. For example, when it is assumed that the transmission data becomes abnormal during the transmission of each phase voltage data, there is a concern about malfunction / malfunction. As one of the countermeasures, it is recommended to apply logic that takes into account malfunctions and malfunctions in the event of transmission abnormalities to protective relays that use voltage data. In the normal current differential method, the terminal that has become inactive is zeroed to prevent unnecessary operation. However, regarding the undervoltage relay 27 using the voltage data, if the voltage value is zeroed, the protective relay becomes unnecessary, so another countermeasure is required. For this reason, in the protective relay using voltage data, by combining the condition of transmission abnormality with each phase voltage, the pre-holding of the undervoltage relay 27 condition is carried out in the case of transmission abnormality, and the normal operation is performed when there is no abnormality. By establishing logic so as to be possible, it was possible to provide a protection function equivalent to that of a device by taking in line voltage (LPD).

  The circuit breaker tripping operation at the B end Tb and the C end Tc may be provided with the above-described logic. However, in order to ensure the operation at the representative end, 51 (overcurrent) is provided via the negative circuit N1. Transmit the operation signal of the relay.

  In the above-described multi-terminal protection relay system, information of each terminal is transmitted and used mutually. For this purpose, the transmission format of FIG. Have been used. FIG. 5a shows a transmission format sent out by Ta as a representative end, and FIG. 5b shows a transmission format sent out by B end Tb and C end Tc other than the representative end Ta.

  First, the transmission format Fa transmitted by Ta as the representative end will be described. In FIG. 5, ◯ means information used for the protection operation, Δ means reference information for display, and X means nonuse information.

  In the case of the representative end Ta, information on the idle end of the frame F1, operation information (87S, 87G) of the current differential protection relay of the frame F3, each phase voltage (including zero phase) of the frame F6, and transmission of the frame F7 The defect information is information used for the protection operation, and the frame F4 is not used (there is no information to be loaded). Information is placed in other frames, but use on the receiving side is only reference information. In the case of the B end Tb and the C end Tc, the information on the idle end of the frame F1, the operation information of the overcurrent relay 51 of the frame F4, and the current information of the frame F5 are information used for the protection operation, and the frame F3, F6 is not used. There is no information to put in these frames. Information is put on the frame F2, but it is only for reference. In this frame, the terminal F1 pause end information is transmitted with each terminal carrying the state of the accident.

  The protection relay system for a multi-terminal power transmission system according to the present invention can perform a reliable protection operation as described above even when it has a variable power supply end or a non-power supply end. And when a representative end turns into a dormant end, a driving | running can be continued by changing into the following driving | operation modes.

  Next, an operation when the representative end is changed will be described. In addition, there are several conditions for the representative end to be the dormant end, such as inspection of the protective relay device and opening of the circuit breaker. Here, it is possible to continue operation of the protective relay system at the time of inspection of the protective relay device. This will be explained. In addition, since the protection relay system of the multi-terminal power transmission system targeted in the present invention assumes the case of having a variable power supply end or a non-power supply end, the representative end that is the only power supply end is a condition that the circuit breaker is open. In the state where it becomes a dormant end, the continuous operation of the protective relay operation by changing the representative end cannot be performed.

  When the protective relay device at the representative end Ta is inspected and treated as a dormant end, the B end is assumed to be the representative end according to priority, as will be described later with reference to FIG. The fact that the representative end Ta has become a pause end is described in the frame F1 in FIG. 4 and is notified to the other end, and the terminal representative end signal of the circuit in FIG. X is changed to “1” or “0”. In this case, the local end representative signal X is changed from “1” to “0” at the A end, and the circuit configuration is as shown in FIG. At the B end, the local representative end signal X is changed from “0” to “1”, and the circuit configuration is as shown in FIG. The C end remains as in FIG. 7b.

  Even in this state, the A-end transmission unit (FIGS. 3 and 5a) forms the transmission format (FIG. 5) as before, and continues to send all the information detected at the A-end. That is, the format is formed in the state where F3 of the frame in FIG. 5a changes to x, F4 changes to ○, and the handling of F5 changes from Δ to ○, and signal transmission is continued. Therefore, the information necessary for the protective relay operation at the B end, which has become the new representative end, is secured, and there is no problem in the protective relay operation.

  Further, regarding the A end of the resting end, it is necessary to perform the tripping operation of the circuit breaker in response to the transfer interruption signal from the representative end although it is being inspected. In order to make this possible, it is possible to use the part other than the circuit in FIG. 7b as an inspection target and make use of the circuit in FIG. 7b, or to enter the forced interruption during the pause end inspection and on condition of receiving the transfer interruption signal. It is done.

  Next, as another example of transmitting the other end information and utilizing it for the protection relay operation, an example of a ground fault detection current differential protection relay 87G will be described.

  In the apparatus configuration of FIG. 1, a ground fault detection current differential protection relay 87G, which is a main element for detecting an internal failure of the multi-terminal power transmission system, is configured as shown in FIG. As specific processing of 87G, current data sampled at the same time at each terminal in FIG. 2 is collected at the representative terminal Ta by the transmission device 8, and a vector sum (zero phase current) of each terminal current is used by using this data. Current differential protection is performed in the processing unit 6a using the operation amount and the scalar sum as the suppression amount. In FIG. 8, the difference current calculation unit 30 performs this process. As for the phase characteristics, when the phase comparison unit 31 performs the calculation with the zero-phase voltage and the zero-phase difference current and exceeds the operating range, the relay operation is performed.

  In FIG. 8, the zero-phase voltage used in the phase comparison unit 31 is selected by the representative end selection circuit 32 and used. The representative end selection circuit 32 has the zero-phase voltage 33 detected at each terminal and the pause information 34 of each terminal, and the priority selection circuit 35 selects the zero-phase voltage at one terminal in the order of superiority. In the illustrated priority selection circuit 35, priorities are set in the order of A end, B end, and C end.

  Thereby, since the A end (parent end) is the representative end at the beginning, the zero-phase voltage of the A end is input to the phase comparison unit 31 of the 87 G relay at the A end, and the A end (representative end) failure determination is performed. Can be used. If the A end, which is the representative end, is suspended, the B end (child end) with the next highest priority is selected as the representative end, and the 87G relay at the B end can be used. As the zero-phase voltage, the B zero-phase voltage is input and can be used for failure determination at the B end (representative end). Hereinafter, even when the C end is selected, the 87G relay at the C end can be used. The zero-phase voltage used as the zero-phase voltage is input, and the C-end (representative end) is connected. Can be used for failure determination.

  However, in the condition where the bus voltage at the B end and the C end cannot be obtained, the continuous operation can be performed by using the A-end voltage via the transmission line instead of the zero-phase voltage 33.

  The concept of the dominant line selection circuit 34 is used for switching the zero-phase voltage used in the 87G relay here, but may be a condition for generating the self-end representative terminal signal X in FIG. That is, the selection logic based on the priority order can be used as the logic for determining the representative end from the pause end information reported by each terminal.

  Further, by enabling transmission of each phase voltage data, it is possible to apply a relay of voltage elements that could not be implemented until now in a system that takes in the bus voltage. In the protection relay device using the voltage data of FIG. 1, an undervoltage relay is described as an example. However, depending on the use of protection control and the contents of the transmission format, it can be applied to various protection relays for voltage elements and current elements. Also good.

  According to the present invention described above, the following effects can be expected. First, according to the conventional technique, the terminal that has become inactive is zeroed to prevent unnecessary operation. When the A terminal that implements the 87G relay becomes the idle terminal, the calculation cannot be performed, and the current value is zeroed and a lock signal is transmitted to each terminal through the transmission device to prevent unnecessary operations. Was. In this respect, since the device according to the present invention performs protective relay calculation by transmitting voltage / current data at a plurality of terminals, 87G relay calculation can be performed at each end even in a system using bus voltage acquisition.

  Further, in the conventional specification, the representative end where the 87G relay is provided is determined in advance and the operation information is transmitted to each end. However, in the present invention, the 87G relay is provided at each end, and a pause at each end is detected. As a result, a method for selecting a representative end was established. Thereby, it is possible to follow the conventional idea and improve the stability of the system.

  Furthermore, by enabling transmission of each phase voltage data, it is possible to apply a relay of a voltage element such as an undervoltage relay, which could not be implemented until now, to improve the stability of the system. It is possible.

  Since multi-terminal power transmission systems including variable power supply terminals or non-power supply terminals are increasing, it can be widely used as a protective relay system in this case.

1: Back power supply 2: Non-power supply end 3: Variable power supply end 4: Signal transmission path 5: Transmission unit 6: Arithmetic processing unit 8: Signal transmission device L: Transmission line Ta: A end Tb: B end Tc: C end RY : Protection relay device BPD: Bus voltage detector F1: Control information such as pause end F2: Opening / closing information of equipment such as self-breaker and line switch F3: Calculation result information of current differential protection relay device (earth fault detection For short circuit detection)
F4: Ground fault detection signal 51 (ground fault overcurrent relay)
F5: Each terminal current (each phase current, zero phase current)
F6: Each terminal voltage (each phase voltage, zero phase voltage)
F7: Transmission failure information A1-A6: AND circuit N1, N2: negative circuit OR1, OR2: OR circuit X: own terminal representative signal 27: undervoltage relay 51: overcurrent relay 64: ground fault overvoltage relay 87S: short circuit detection Current differential protection relay 87G: Current differential protection relay for ground fault detection

Claims (4)

In a protective relay system for multi-terminal power transmission systems that include variable power supply terminals or non-power supply terminals in addition to power supply terminals,
The protective relay device of each terminal includes a parent device circuit that performs current operation calculation and a child device circuit that does not perform current differential operation. Normally, the parent device circuit is selected at the power supply terminal, and the child device is selected at the other terminals. Select the circuit,
The transmission unit of each terminal transmits self-end detection information necessary for the current differential calculation of the parent device circuit,
The transmission section at the power supply further transmits the power supply bus voltage,
The protective relay device at the power supply terminal operates the self-breaker with the current differential calculation result of the parent device circuit, and transmits the current differential calculation result to another terminal.
The protection device for the multi-terminal power transmission system is characterized in that the slave device circuit of the other terminal operates a self-end circuit breaker from the power supply end bus voltage sent from the power supply end side and the current differential calculation result. Relay system. In the protective relay system of the multi-terminal power transmission system according to item 1,
The transmission unit of each terminal transmits information that its own end is a pause end,
The protective relay device of each terminal determines whether the self-end is a parent device circuit or a sub-device circuit according to the priority order determination that places the power supply end as the first using the information on the sleep end. A protective relay system for multi-terminal power transmission systems. In the protective relay system of the multi-terminal power transmission system according to item 1,
The transmission unit at the power supply end transmits the power supply bus voltage even when the protective relay device other than the power supply end selects the parent device circuit,
The protective relay device of the terminal that has selected the parent device circuit operates the self-breaker with the current differential calculation result of the parent device circuit, and transmits the current differential calculation result to the other terminals.
A protection relay system for a multi-terminal power transmission system, wherein the slave device circuit of the other terminal operates the self-end circuit breaker from the current differential calculation result. In the protective relay system of the multi-terminal power transmission system according to item 1,
The transmission part of each terminal transmits information including transmission abnormality information.
When the power supply terminal bus voltage sent from the power supply terminal side is used, the slave device circuit of the other terminal uses the information of the transmission abnormality to prevent unauthorized operation of the protective relay using the power supply bus voltage. A protective relay system for multi-terminal power transmission systems.

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