JP2017195716A - Power transmission line protection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a power transmission line protection system which can be protected by a simple circuit structure.SOLUTION: An electric power substation includes a plurality of power transmission circuits 5 and 7 connected to a power incoming circuit 1 through a transformer 3 and a power transmission bus bar 4, and comprises: a current transformer 10 that detects a current of the power incoming circuit 1; an overcurrent relay 12 for a backup protection that is operated by the current of the current transformer 10; a current transformer 20 that detects the current of the power transmission circuit 5; an overcurrent relay 21 that is operated by the current of the current transformer 20 and protects the power transmission circuit 5; a current transformer 30 that detects the current of the power transmission circuit 7; and an overcurrent relay 31 that is operated by the current of the current transformer 30 and protects the power transmission circuit 7. The overcurrent relay 21 includes a fault monitoring function that outputs a fault detection signal when the electric power substation itself is broken down. In a case where a short circuit accident occurs in the power transmission circuit 5 when braking down the overcurrent relay 21, the accident is detected by the overcurrent relay 12 for a backup protection, a circuit breaker 6 as a circuit breaker to be executed the backup protection is specified on the basis of the fault detection signal, and the circuit breaker 6 is tripped.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power transmission line protection system.

  In conventional low-voltage substations, for example, load supply substations, there is no protection when the load supply line protection relay fails, so if an accident occurs, the upper-level transformer protection relay functions as a backup protection relay. There was a problem that a high-order transformer, etc., tripped, and other healthy load supply lines were also blacked out, causing a wide range of supply problems. On the other hand, by installing a trip device that utilizes a transformer protection relay, by taking in the operating state (open / closed state) of the circuit breaker of the load supply line (transmission line) to be protected, On the other hand, a power transmission line alternative protection system has been proposed as a power transmission line protection system capable of tripping the corresponding load supply line and bus line in a stepwise manner (for example, see Patent Document 1).

Japanese Patent Laying-Open No. 2011-199962 (paragraph numbers 0017 to 0052 and FIG. 4)

  The conventional power transmission line protection system is configured as described above, and it is necessary to capture the operation state of the circuit breaker as many as the number of power transmission lines to be protected. As the number of power transmission lines increases, the circuit configuration becomes complicated. there were.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a power transmission line protection system capable of protection with a simple configuration.

In the power transmission line protection system according to the present invention,
A power transmission line protection system for protecting a plurality of power transmission lines connected to a power reception line, comprising a first abnormality detection device, a second abnormality detection device or a third abnormality detection device, and a protection command transmission device,
The first abnormality detection device has a self-monitoring function that detects a failure of itself and issues a failure detection signal, and is provided for each of the power transmission lines and detects a failure for each of the power transmission lines and issues a first detection signal. Is,
The second abnormality detection device is connected to the power receiving line, detects an abnormality of the power transmission line, and issues a second detection signal;
The third abnormality detection device is provided in common with the first abnormality detection device, and detects an abnormality in the power transmission line in place of the first abnormality detection device that has failed even if any of the first abnormality detection devices fails. The detection is enabled and a third detection signal is issued when the abnormality is detected,
The protection command transmission device transmits a protection command by specifying the power transmission line to be protected based on the failure detection signal and the second detection signal, or the failure detection signal and the third detection signal. .

A power transmission line protection system according to the present invention includes:
It protects multiple power transmission lines connected to the power reception line,
A first abnormality detection device which has a self-monitoring function for detecting a failure of itself and issuing a failure detection signal, which is provided for each transmission line and which detects a failure for each transmission line and issues a first detection signal;
A second abnormality detection device that is connected to the power reception line and detects a power transmission line abnormality to generate a second detection signal;
When it is provided in common with the first abnormality detection device and the abnormality of the power transmission line can be detected in place of the first abnormality detection device which has failed even if any one of the first abnormality detection devices fails, and the abnormality is detected A third abnormality detection device for emitting a third detection signal;
Since it has a protection command transmission device that specifies a power transmission line to be protected based on the failure detection signal and the second detection signal, or the failure detection signal and the third detection signal, and transmits a protection command,
A power transmission line protection system that can be protected with a simple configuration can be obtained.

It is a block diagram which shows the structure of the power transmission line protection system which is Embodiment 1 of this invention. FIG. 6 is an explanatory diagram showing a flow of current when a short circuit accident occurs in the first embodiment. FIG. 6 is an exploded connection diagram for explaining the operation of the power transmission line protection system in the first embodiment. It is a block diagram which shows the structure of the power transmission line protection system which is Embodiment 2. FIG. It is explanatory drawing which shows the flow of an electric current when the short circuit accident in Embodiment 2 generate | occur | produces. FIG. 10 is a developed connection diagram for explaining the operation of the power transmission line protection system in the second embodiment. FIG. 10 is a configuration diagram illustrating a configuration of a power transmission line protection system according to a third embodiment. FIG. 10 is an explanatory diagram showing a current flow when a short circuit accident occurs in the third embodiment. FIG. 10 is a developed connection diagram for explaining the operation of a power transmission line protection system in a third embodiment. It is explanatory drawing which shows the flow of an electric current when a short circuit accident generate | occur | produces while the overcurrent relay is out of order. It is explanatory drawing which shows the flow of an electric current when a short circuit accident generate | occur | produces while another overcurrent relay fails.

Embodiment 1 FIG.
1 to 3 show a first embodiment for carrying out the present invention. FIG. 1 is a configuration diagram showing a configuration of a power transmission line protection system, and FIG. 2 is a diagram of current when a short-circuit accident occurs. FIG. 3 is a developed connection diagram for explaining the operation of the power transmission line protection system. In FIG. 1, the main circuit of a substation as a power system is configured as follows. A transformer 3 is connected to the power receiving line 1 through a circuit breaker 2. A power transmission bus 4 is connected to the secondary side of the transformer 3. A series circuit of a power transmission line 5 and a circuit breaker 6 and a series circuit of a power transmission line 7 and a circuit breaker 8 are connected to the power transmission bus 4, and the power transmission line 5 and the power transmission line 6 are connected to the circuit breakers 6 and 8. Further, power is sent to a subordinate substation (not shown).

  The power transmission line protection system is configured as follows. The power receiving line 1 is provided with a current transformer 10, an overcurrent relay (OCR) 11 as a protection relay on the secondary side of the current transformer 10, and an overcurrent relay 12 as a back-up protection and second abnormality detection device. And are connected. The output signal side of the overcurrent relay 11 is connected to the control circuit 14. The control circuit 14 is connected to a switchgear (not shown) of the circuit breaker 2. The output signal side of the overcurrent relay 12 is connected to an auxiliary relay (AXR) 13. The auxiliary relay 13 has a coil 13C, and amplifies the output signal of the overcurrent relay 12, that is, converts it to an opening / closing signal of the contact 13a through which a larger current can flow.

  A current transformer 20 is provided in the power transmission line 5, and an overcurrent relay 21 serving as a first abnormality detection device is connected to the secondary side of the current transformer 20. The output signal side of the overcurrent relay 21 is connected to the control circuit 22. The control circuit 22 is connected to a switchgear (not shown) of the circuit breaker 6. A current transformer 30 is provided in the power transmission line 7, and an overcurrent relay 31 serving as a first abnormality detection device is connected to the secondary side of the current transformer 30. The output signal side of the overcurrent relay 31 is connected to the control circuit 32. The control circuit 32 is connected to a switchgear (not shown) of the circuit breaker 8. The output side of the auxiliary relay 13 is connected to the control circuits 22 and 32. The overcurrent relay 12 has a self-monitoring function for constantly monitoring its own internal failure in addition to the normally open contact 12a that is closed when the overcurrent relay 12 is operated, and detects a failure when no internal failure is detected. The contact 12x is opened, and the failure detection contact 12y is closed. When an internal failure is detected in the overcurrent relay 12, the failure detection contact 12x is closed and the failure detection contact 12y is opened (see FIG. 3).

  As shown in FIG. 3, the overcurrent relay 21 has a self-monitoring function for constantly monitoring its own internal failure in addition to the normally-open contact 21a that is closed when operated, and when no internal failure is detected. The failure detection contact 21x is opened and the failure detection contact 21y is closed. In the overcurrent relay 21, when an internal failure is detected, the failure detection contact 21x is closed and the failure detection contact 21y is opened (see FIG. 3). Although not shown, the same applies to the overcurrent relay 31. DC power is supplied to the overcurrent relay 11 and the overcurrent relay 12 from the control power supply lines P1 and N1. The overcurrent relay 21 and the overcurrent relay 31 are supplied with DC power from the control power supply lines P2 and N2. In this embodiment, the overcurrent relay 21 and the overcurrent relay 31 are realized by software processing by digital control using a microprocessor or a digital signal processor (a digital relay having a self-monitoring function). Yes. The overcurrent relay 12, the auxiliary relay 13, the overcurrent relay 21, the control circuit 22, the overcurrent relay 31, and the control circuit 32 are the protection command transmission device in the present invention.

  Next, the operation will be described. As shown in FIG. 2, when the main circuit is short-circuited at the fault point F1, the fault current J1 flows on the primary side of the transformer 3, and the overcurrent relay 11 connected to the secondary side of the current transformer 10 is provided. A current C1 flows through the protective overcurrent relay 12. The fault current J2 flows on the secondary side of the transformer 3, and the current C2 flows in the overcurrent relay 21 connected to the secondary side of the current transformer 20. If there is no abnormality in all of the overcurrent relay 11, overcurrent relay 12, and overcurrent relay 21, the overcurrent relay 21 close to the fault point F1 operates due to the magnitude relationship between the settling value and the settling time, and serves as the first detection signal. The normally open contact 21a is closed, and a voltage is applied to the coil 22C of the control circuit 22 from the control power supply lines P2 and N2 to be excited. When the coil 22C is energized, a switching contact signal (not shown) of the coil 22C as a protection command is output as a circuit breaker trip signal to the switching device of the circuit breaker 6 to open the circuit breaker 6 and to open the fault point F1. Disconnection from the power transmission bus 4 is completed.

  Next, the case where the overcurrent relay 21 of the power transmission line 5 is broken will be described with reference to FIG. In FIG. 3, when the overcurrent relay 21 of the power transmission line 5 is out of order, the failure detection contact 21x as a failure detection signal of the overcurrent relay 21 of the power transmission line 5 is closed. In this state, when the overcurrent relay 12 for protection of protection provided in the power receiving line 1 is operated, a voltage is applied from the control power supply lines P1 and N1 to the coil 13C of the auxiliary relay 13 by closing the normally open contact 12a as the second detection signal. Applied and excited, the contact 13a is closed. When the contact point 13a is closed, the failure detection contact point 21x of the overcurrent relay 21 is closed, so that a voltage is applied to the coil 22C of the control circuit 22 from the control power supply lines P2 and N2, and the normally open contact point is applied. (Not shown) is closed. The normally open contact closing signal is sent to the switchgear of the circuit breaker 6 to open the circuit breaker 6 and the fault point F1 is disconnected from the power transmission bus 4. Although the current C1 flows into the overcurrent relay 11 at the time of the short-circuit accident, the overcurrent relay 12 operates due to the magnitude relationship between the set values of the overcurrent relay 11 and the overcurrent relay 12 and the settling time, and is close to the accident point F1. The circuit breaker 6 is opened and the circuit breaker 2 is not opened.

  When the overcurrent relay 31 fails, the circuit breaker 8 is opened in the same manner as when the overcurrent relay 21 fails.

  As described above, according to this embodiment, the overcurrent relay 21 and the overcurrent relay 31 having a self-monitoring function for detecting a self-failure and generating a fault detection signal are provided. Since the overcurrent relay 12 identifies the power transmission line to be protected after the protection and issues a protection command to protect the power transmission line, the circuit breaker 6 provided in the power transmission line 5 and the interruption provided in the power transmission line 7 It is not necessary to use information on the open / close state of the container 8. Therefore, the complexity of the circuit configuration can be suppressed as the number of power transmission lines increases, and a power transmission line protection system with a simple configuration can be obtained.

Embodiment 2. FIG.
4 to 6 show the second embodiment. FIG. 4 is a configuration diagram showing the configuration of the power transmission line protection system. FIG. 5 is an explanatory diagram showing the flow of current when a short circuit accident occurs. 6 is a developed connection diagram for explaining the operation of the power transmission line protection system. The first embodiment is characterized in that an overcurrent relay 12 is provided in the power receiving line 1. On the other hand, in this embodiment, as shown in FIG. 4, an overcurrent relay 42 serving as a back-end protection and a third abnormality detection device is provided on the power transmission line 5 and the power transmission line 7 side. The overcurrent relay 42 is connected such that the currents of both the current transformer 20 and the current transformer 30 are added (the sum of the currents of all transmission lines) flows, that is, supplied. The overcurrent relay 42 is provided as a back-up device common to the overcurrent relay 21 and the overcurrent relay 31.

  The output signal side of the overcurrent relay 42 is connected to the auxiliary relay 43, and the output signal is converted into an opening / closing signal of the contact 43a that can flow a larger current. The overcurrent relay 42 has a self-monitoring function for constantly monitoring its own internal failure in addition to the normally open contact 42a that is closed when the overcurrent relay 42 is operated, and detects a failure when no internal failure is detected. The contact 42x is opened, and the failure detection contact 42y is closed. When an internal failure is detected in the overcurrent relay 42, the failure detection contact 42x is closed and the failure detection contact 42y is opened (see FIG. 6). Since other configurations are the same as those in the first embodiment, the corresponding components are denoted by the same reference numerals and description thereof is omitted. The overcurrent relay 21, the control circuit 22, the overcurrent relay 31, the control circuit 32, the overcurrent relay 42, and the auxiliary relay 43 are the protection command transmission device in the present invention.

  Next, the operation will be described. As shown in FIG. 5, when the main circuit is short-circuited at the fault point F1, the fault current J1 flows through the power receiving line 1, and the overcurrent relay 11 and the overcurrent relay 12 connected to the current transformer 10 have the current C1. Flowing. The fault current J2 flows through the secondary side of the transformer 3, and the current C3 flows through the overcurrent relay 21 and the overcurrent relay 42 connected to the current transformer 20. At this time, if all of the overcurrent relay 11, the overcurrent relay 12, the overcurrent relay 21, and the overcurrent relay 42 are not abnormal, the overcurrent relay 21 that is close to the accident point is operated depending on the magnitude relationship between the set value and the settling time. Then, the normally open contact 21a is closed (the failure detection contact 21y is closed), and the coil 22C of the control circuit 22 is excited (see FIG. 6). When the coil 22C is excited, the switching contact signal is output to the switching device of the circuit breaker 6 as a circuit breaker trip signal, and the circuit breaker 6 is opened.

  Hereinafter, the case where the overcurrent relay 21 has failed will be described. In FIG. 6, when the overcurrent relay 42 operates and the normally open contact 42a as the third detection signal is closed, the coil 43C of the auxiliary relay 43 is excited and the contact 43a is closed. At this time, if the overcurrent relay 21 is faulty, the fault detection contact 21x is closed and the fault detection contact 21y is open, so the control power supply lines P2 and N2 are connected via the fault detection contact 21x and the contact 43a. A voltage is applied to the coil 22C of the control circuit 22 to excite it. When the coil 22C is energized, an opening / closing signal of the switching contact of the coil 22C as a protection command is output as a circuit breaker trip signal to the switching device of the circuit breaker 6 to open the circuit breaker 6 and the overcurrent relay 21 is normal. In the same manner as in the case of the above, the disconnection of the accident point F1 from the power transmission bus 4 is completed.

  Similarly to the case where the overcurrent relay 21 is out of order when the overcurrent relay 31 is faulty, the fault current detected by the current transformer 30 is detected in the overcurrent relay 42 when a short circuit occurs at the fault point F1. The overcurrent relay 42 operates and the circuit breaker 8 is opened. Since the sum of the currents flowing through the power transmission line 5 and the power transmission line 7 flows through the overcurrent relay 42, the set value of the overcurrent relay 42 is smaller than the sum of the maximum load currents of the power transmission line 5 and the power transmission line 7, respectively. When the value is set to a value, the operation of the overcurrent relay 42 causes the circuit breaker 6 to be opened when the overcurrent relay 21 is faulty, and when the overcurrent relay 31 is faulty, the circuit breaker 8 is It will be opened.

  As described above, according to this embodiment, the failure detection signal of the overcurrent relay 21 and the overcurrent relay 31 and the power transmission line to be protected by the overcurrent relay 42 for the protection of the back-up are identified and the power transmission line is defined. Since the protection command for protection is issued, it is not necessary to use information on the open / close state of the circuit breaker 6 provided in the power transmission line 5 or the circuit breaker 8 provided in the power transmission line 7. Therefore, the complexity of the circuit configuration can be suppressed as the number of power transmission lines increases, and a power transmission line protection system with a simple configuration can be obtained.

  In the first embodiment shown in FIG. 1, since the overcurrent relay 12 is provided for the protection of the power transmission lines 5 and 7 in the power receiving line 1, the difference in voltage class must be taken into account when setting the protection. On the other hand, in the second embodiment, since the overcurrent relay 42 for the back-end protection is provided on the side of the transmission lines 5 and 7 having the same voltage class, the setting of the overcurrent relay 42 can be easily studied.

Embodiment 3 FIG.
7 to 11 show the third embodiment. FIG. 7 is a configuration diagram showing the configuration of the power transmission line protection system. FIG. 8 is an explanatory diagram showing the flow of current when a short-circuit accident occurs. 9 is a developed connection diagram for explaining the operation of the power transmission line protection system. FIG. 10 is an explanatory diagram showing the flow of current when a short circuit accident occurs while the overcurrent relay is out of order. FIG. 11 is an explanatory diagram showing the flow of current when a short circuit accident occurs while another overcurrent relay fails. The second embodiment is characterized in that an overcurrent relay 42 to which detection currents of both the current transformer 20 and the current transformer 30 are supplied is provided. On the other hand, in this embodiment, as shown in FIG. 7, switching devices 51 and 52 are provided as current switching units that switch and supply the detected currents of the current transformer 20 and the current transformer 30. And In FIG. 7, an overcurrent relay 21 and a switch 51 are connected to the secondary side of the current transformer 20. An overcurrent relay 31 and a switch 52 are connected to the secondary side of the current transformer 30.

  An overcurrent relay 54 as a back-up protection and third abnormality detection device is connected to the overcurrent relay 21 through the switch 51 and is connected to the overcurrent relay 31 through the switch 52. The output signal side of the overcurrent relay 54 is connected to the auxiliary relay 55, and the output signal is converted into an opening / closing signal of the contact 55a that can flow a larger current. The overcurrent relay 54 has a self-monitoring function for constantly monitoring its own internal fault in addition to the normally open contact 54a that is closed when the overcurrent relay 54 is operated, and detects a fault when no internal fault is detected. The contact 54x is opened, and the failure detection contact 54y is closed. When an internal failure is detected in the overcurrent relay 54, the failure detection contact 54x is closed and the failure detection contact 54y is opened (see FIG. 8). Since other configurations are the same as those in the second embodiment, the corresponding components are denoted by the same reference numerals and description thereof is omitted. In this case as well, the overcurrent relay 54 is provided as a function that serves as a common back-up device for the overcurrent relay 21 and the overcurrent relay 31. The overcurrent relay 21, the control circuit 22, the overcurrent relay 31, the control circuit 32, the overcurrent relay 54, and the auxiliary relay 55 are the protection command transmission device in the present invention.

  Next, the operation will be described. In FIG. 7, when the overcurrent relay 21 is not out of order, the switch 51 is not excited, the two contacts 51a are opened, the contact 51b is closed, and the overcurrent relay 21 is transformed. The overcurrent relay 54 is not connected to the current transformer 20. Similarly, when the overcurrent relay 31 is not faulty, the switch 52 is not excited, the two contacts 52a shown in FIG. 7 are opened, and the contact 52b is closed, so that the overcurrent relay is closed. 31 is connected to the current transformer 30, and the overcurrent relay 54 is not connected to the current transformer 30. In this normal state, when the main circuit is short-circuited at the fault point F1, the fault current J1 flows on the primary side of the transformer 3 and the fault current J2 on the secondary side of the transformer 3 as shown in FIG. Each flows. A current C1 that is a secondary current of the current transformer 10 flows in the overcurrent relay 11 and the overcurrent relay 12, and a current C2 that is a secondary current of the current transformer 20 flows in the overcurrent relay 21. By setting each of the overcurrent relays 11, 12, and 21, the overcurrent relay 21 closest to the fault point F <b> 1 is operated to open the circuit breaker 6.

  On the other hand, when the overcurrent relay 21 has failed, the failure detection contact 21x as a failure detection signal of the overcurrent relay 21 shown in FIG. 9 is closed and the failure detection contact 21y is opened. When the failure detection contact 21x is closed, the coil 51C of the switch 51 is excited, the two contacts 51a (FIG. 7) are closed, and the contact 51b (FIG. 7) is opened. As a result, the overcurrent relay 54 is connected to the current transformer 20, and when the fault current J2 flows to the current transformer 20, the secondary current C4 of the current transformer 20 is changed to the overcurrent relay 54 in FIG. Flow, or supply, as shown. Then, the overcurrent relay 54 operates, the normally open contact 54a as the third detection signal is closed (FIG. 9), and the control power line P2, via the normally open contact 54a and the failure detection contact 54y (closed). A voltage is applied from N2 to the coil 55C of the auxiliary relay 55 to be excited, and the contact 55a is closed. When the contact point 55a is closed, the overcurrent relay 21 breaks down and the failure detection contact point 21x is closed. Therefore, the coil 22C of the control circuit 22 is excited via the diode 55d and opens and closes the coil 22C as a protection command. The contact opening / closing signal is output as a circuit breaker trip signal to the switchgear of the circuit breaker 6, and the circuit breaker 6 is opened.

  When the overcurrent relay 31 fails, the coil (not shown) of the switch 52 is similarly excited, the two contacts 52a (FIG. 7) are closed, and the contact 52b (FIG. 7) is opened. As a result, when the overcurrent relay 54 is connected to the current transformer 30 and a short circuit accident occurs on the load side of the circuit breaker 8, the current transformer 30 is connected to the overcurrent relay 54 as shown in FIG. The secondary current C5 flows, the overcurrent relay 54 operates, and the circuit breaker 8 is opened.

  As described above, according to this embodiment, the failure detection signal of the overcurrent relay 21 and the overcurrent relay 31 and the power transmission line to be protected by the overcurrent relay 42 for the protection of the back-up are identified and the power transmission line is defined. Since the protection command for protection is issued, it is not necessary to use information on the open / close state of the circuit breaker 6 provided in the power transmission line 5 or the circuit breaker 8 provided in the power transmission line 7. Therefore, the complexity of the circuit configuration can be suppressed as the number of power transmission lines increases, and a power transmission line protection system with a simple configuration can be obtained.

  In the second embodiment, the sum of the currents of the power transmission line 5 and the power transmission line 7 which is the sum of the currents of all the power transmission lines is supplied (the sum is taken in). It is configured so that the current of only the power transmission line handled by the overcurrent relay is supplied. Therefore, in the second embodiment, when the sum of the load currents flowing through the respective transmission lines increases, malfunction of the overcurrent relay 42 for the back-end protection is likely to occur, whereas in this third embodiment, for the back-end protection. By supplying only the necessary current, malfunctions are less likely to occur, and a more reliable power transmission line protection system can be obtained.

In the above embodiment, two power transmission lines are used. However, the same effect can be obtained even if three or more lines are used, and the effect of the present invention is further enhanced if the number of lines is increased.
In addition, the abnormal phenomenon to be protected is not limited to overcurrent, but may be other abnormality detection such as detection of overload, or a substation where the power receiving line or power transmission line is DC. However, the same effect can be obtained.

  In the present invention, the above-described embodiments can be freely combined within the scope of the invention, or each embodiment can be appropriately changed or omitted.

1 power receiving line, 3 transformer, 5, 7 power transmission line, 10 current transformer, 12 overcurrent relay, 13 auxiliary relay, 14 control circuit, 20 current transformer, 21 overcurrent relay,
22 control circuit, 30 current transformer, 31 overcurrent relay, 32 control circuit,
42 Overcurrent relay, 43 Auxiliary relay, 51, 52 selector, 54 Overcurrent relay,
55 Auxiliary relay.

Claims (6)

A power transmission line protection system for protecting a plurality of power transmission lines connected to a power reception line, comprising a first abnormality detection device, a second abnormality detection device or a third abnormality detection device, and a protection command transmission device,
The first abnormality detection device has a self-monitoring function that detects a failure of itself and issues a failure detection signal, and is provided for each of the power transmission lines and detects a failure for each of the power transmission lines and issues a first detection signal. Is,
The second abnormality detection device is connected to the power receiving line, detects an abnormality of the power transmission line, and issues a second detection signal;
The third abnormality detection device is provided in common with the first abnormality detection device, and detects an abnormality in the power transmission line in place of the first abnormality detection device that has failed even if any of the first abnormality detection devices fails. The detection is enabled and a third detection signal is issued when the abnormality is detected,
The protection command transmission device transmits a protection command by specifying the power transmission line to be protected based on the failure detection signal and the second detection signal, or the failure detection signal and the third detection signal. Transmission line protection system. The first abnormality detection device and the second abnormality detection device or the third abnormality detection device both detect an overcurrent,
The first abnormality detection device detects an overcurrent of the power transmission line based on a detection current of a current transformer that detects a current of the power transmission line, and issues the first detection signal.
The second abnormality detection device detects an overcurrent of the power receiving line and issues the second detection signal;
The third abnormality detection device can detect the overcurrent of the power transmission line based on the detection current of the current transformer instead of the failed first abnormality detection device when the first abnormality detection device fails. The power transmission line protection system according to claim 1, wherein the third detection signal is generated when the overcurrent is detected. The third abnormality detection device receives the supply of the detection current of the current transformer corresponding to the failed first abnormality detection device when the first abnormality detection device fails and receives the overcurrent of the transmission line. The transmission line protection system according to claim 2, which detects and issues the third detection signal. The third abnormality detection device receives the sum of the detection currents of all the current transformers, detects the overcurrent of the power transmission line, and generates the third detection signal. The transmission line protection system described. A current switching unit that switches a supply destination of the detection current of the current transformer between the first abnormality detection device and the third abnormality detection device; and the third abnormality detection device includes the first abnormality detection When the device fails, the detection current of the current transformer corresponding to the failed first abnormality detection device is supplied via the current switching unit to detect the overcurrent of the power transmission line, and the third detection The power transmission line protection system according to claim 3, which emits a signal. The power transmission line protection system according to any one of claims 1 to 5, wherein the power reception line and the plurality of power transmission lines are connected via a transformer.

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