JP2024058169A - Busbar protection device, power receiving equipment, and busbar protection method - Google Patents

Abstract

[Problem] To eliminate the influence of blind spots and remove accidents even when a current transformer is arranged on the secondary side of a circuit breaker to reduce installation space. [Solution] A busbar protection device according to an embodiment is used in a power receiving facility having a plurality of individual busbars constituting a plurality of parallel circuits, a common busbar that can be commonly connected to the plurality of individual busbars, a common current transformer provided on the common busbar side of a common circuit breaker provided at a connection point between the common busbar and the plurality of individual busbars, a plurality of current transformers provided on the individual busbar sides of the common circuit breaker, and a plurality of individual circuit breakers provided on each of the individual busbars and that cut off the corresponding individual busbar when the common circuit breaker is in an open state. When a busbar accident on the common busbar is detected by a busbar accident detection unit based on the output of the common current transformer, a first accident response unit cuts off the common circuit breaker, and when a busbar accident on the corresponding individual busbar is detected based on the output of any of the plurality of current transformers after the common circuit breaker has been opened, a second accident response unit cuts off the corresponding individual circuit breaker. [Selected Figure] Figure 1

Description

Embodiments of the present invention relate to a busbar protection device, a power receiving equipment, and a busbar protection method.

2. Description of the Related Art Conventionally, in a power receiving facility with two parallel circuits (system A and system B), a circuit of the power receiving facility may be constructed that allows a common bus to be connected to the system A bus and the system B bus.
In the above configuration, under normal circumstances, power is distributed to each load via the A-system busbar and the B-system busbar.

JP 2009-05731 A

In contrast, during power line inspections, a common bus was used to maintain the two parallel lines, and the line was operated while maintaining power reception from the two parallel lines.
Conventionally, current transformers have been arranged on the primary and secondary sides of a circuit breaker in order to distinguish between a busbar fault on the common busbar and the A-system busbar and a busbar fault on the B-system busbar.

This could result in a large amount of installation space being required to place the current transformer (CT).

To reduce the installation space required for current transformers (CTs), it is possible to place them on the secondary side of the circuit breaker. However, this creates a blind spot for busbar faults between the circuit breaker and the current transformer. If a busbar fault such as a ground fault occurs in this blind spot, the busbar fault may continue even after the circuit breaker is tripped, and the fault may not be cleared by the busbar protective relay.

The present invention has been made in consideration of the above, and aims to provide a busbar protection device, power receiving equipment, and busbar protection method that can eliminate the effects of blind spots and clear faults using a busbar protection relay, even when the current transformer is placed on the secondary side of the circuit breaker to reduce installation space.

The busbar protection device of the embodiment provides busbar protection for a power receiving facility having a plurality of individual busbars constituting a plurality of parallel circuits, a common busbar that can be commonly connected to the plurality of individual busbars, a common current transformer provided on the common busbar side of a common circuit breaker provided at a connection point between the common busbar and the plurality of individual busbars, a plurality of current transformers provided on the individual busbar sides of the common circuit breaker, and a plurality of individual circuit breakers provided on each of the individual busbars and that cut off the corresponding individual busbar when the common circuit breaker is cut off. The busbar protection device includes a busbar fault detection unit that detects a busbar fault based on the output of the common current transformer and the plurality of current transformers, a first fault response unit that cuts off the common circuit breaker when a busbar fault on the common busbar is detected by the busbar fault detection unit based on the output of the common current transformer, and a second fault response unit that cuts off the corresponding individual circuit breaker when a busbar fault on the corresponding individual busbar is detected based on the output of any of the plurality of current transformers after the common circuit breaker is cut off.

FIG. 1 is a schematic explanatory diagram of a power receiving facility according to an embodiment. FIG. 2 is a functional block diagram of a busbar protective relay according to an embodiment. FIG. 3 is a diagram illustrating normal operation. FIG. 4 is a process flow chart for inspecting a power transmission line. FIG. 5 is an explanatory diagram of a case where a fault on a common bus is detected during an inspection of a power transmission line. FIG. 6 is an explanatory diagram of a case where a fault is detected in a blind spot section during a power line inspection. FIG. 7 is an explanatory diagram of a fault response when the fault current detection point (fault point) is on the bus BA. FIG. 8 is an explanatory diagram of power supply restart.

FIG. 1 is a schematic explanatory diagram of a power receiving facility according to an embodiment.
In the following description, it is assumed that the power receiving equipment 10 includes a common bus BC and buses BA and BB as individual buses.

As shown in FIG. 1 , the power receiving equipment 10 receives power from power distribution lines LA, LB, and LC.
A bus BA is connected to the distribution line LA via a disconnector DS, (current transformer CTA1-3), circuit breakers CBA1-3, and two disconnectors DS. The bus BA is further connected to a common bus BC via a disconnector DS, (current transformer CTC1), (current transformer CTA4), and circuit breaker CBAC.

A load (not shown) is connected to the bus BA via a disconnector DS and a circuit breaker CBA1, and a current transformer CTA1 is provided to detect the current flowing from the circuit breaker CBA1 to the load (not shown) and output an output signal A1.

Similarly, other loads (not shown) are connected via the disconnect switch DS and the circuit breaker CBA2, and a current transformer CTA2 is provided to detect the current flowing from the circuit breaker CBA2 to the other loads (not shown) and output an output signal A2.

Furthermore, a further load (not shown) is connected via the disconnect switch DS and the circuit breaker CBA3, and a current transformer CTA3 is provided which detects the current flowing from the circuit breaker CBA3 to the further load (not shown) and outputs an output signal A3.

A bus BB is connected to the distribution line LB via a disconnector DS, (current transformers CTB1-3), circuit breakers CBA1-3, and two disconnectors DS. The bus BB is further connected to a common bus BC via a disconnector DS, (current transformer CTC2), (current transformer CTB4), and circuit breaker CBBC.
A load (not shown) is connected to the bus BB via a circuit breaker DS and a circuit breaker CBB1, and a current transformer CTB1 is provided which detects the current flowing from the circuit breaker CBB1 to the load (not shown) and outputs an output signal B1.

Similarly, other loads (not shown) are connected via the disconnector DS and the circuit breaker CBB2, and a current transformer CTB2 is provided to detect the current flowing from the circuit breaker CBB2 to the other loads (not shown) and output an output signal B2.

Furthermore, a further load (not shown) is connected via the disconnect switch DS and the circuit breaker CBB3, and a current transformer CTB3 is provided to detect the current flowing from the circuit breaker CBB3 to the further load (not shown) and output an output signal B3.

The busbar BA and busbar BB can be connected via a pair of disconnectors DS and a circuit breaker CBAB. In this case, a current transformer CTA-B is provided between one of the pair of disconnectors DS, which is provided on the busbar BA side, and the circuit breaker CBAB, to detect the current flowing between the busbar BA and busbar BB and output a detection signal.

Similarly, between the other of the pair of disconnectors DS, which is provided on the bus bar BB, and the circuit breaker CBAB, a current transformer CTB-A is provided that detects the current flowing between the bus bar BA and the bus bar BB and outputs a detection signal.

A common bus BC is connected to the distribution line LC via a disconnector DS, (current transformer CTCC), a circuit breaker CBCC, and another disconnector DS.
In addition, between the common bus BC and the bus BA, a disconnector DS, a circuit breaker CBAC, (current transformer CTA4), (current transformer CTC1), and a disconnector DS are provided in the order from the common bus BC to the bus BA.

In addition, between the common bus BC and the bus BB, a disconnector DS, a circuit breaker CBBC, (current transformer CTB4), (current transformer CTC1) and a disconnector DS are provided in the order from the common bus BC to the bus BB.

In the above configuration, the output signal A1 of current transformer CTA1, the output signal A2 of current transformer CTA2, the output signal A3 of current transformer CTA3, the output signal A4 of current transformer CTA4, the output signal of current transformer CTA1-3, and the output signal of current transformer CTB-A are output to the busbar protection relay RLA, which detects an accident in the busbar BA system and cuts off the busbar BA. When the busbar protection relay RLA detects an accident in the busbar BA system, it cuts off the circuit breakers CBA1-3 and CBAB.

In addition, the output signal B1 of current transformer CTB1, the output signal B2 of current transformer CTB2, the output signal B3 of current transformer CTB3, the output signal B4 of current transformer CTB4, the output signal of current transformer CTB1-3, and the output signal of current transformer CTA-B are output to the busbar protection relay RLB, which detects an accident in the busbar BB system and cuts off the busbar BB. When the busbar protection relay RLB detects an accident in the busbar BB system, it cuts off the circuit breakers CBB1-3 and CBAB.

In addition, the output signal C1 of current transformer CTC1, the output signal C2 of current transformer CTC2, and the output signal of current transformer CTCC are output to a busbar protection relay RLC that detects an accident on the common busbar BC and cuts off the common busbar BC. If the busbar protection relay RLC detects an accident on the common busbar BC, it cuts off the circuit breaker CBCC.

Furthermore, if an accident is still detected in the busbar BA system when the circuit breaker CBCC is in the cut-off state, the busbar protection relay RLC performs control to cut off the busbar BA system, assuming that an accident exists in the blind spot section of the busbar BA system.

Furthermore, if no fault is detected in the bus BB system after the bus BA system is cut off, the bus protection relay RLC places the circuit breaker CBCC in a conductive state to supply power from the common bus BC to the bus BB system.

Similarly, if an accident is still detected in the bus BB system when the circuit breaker CBCC is in the cut-off state, the busbar protection relay RLC performs control to cut off the bus BB system, assuming that an accident exists in the blind spot section of the bus BB system.

Furthermore, if no fault is detected in the busbar BA system after the busbar BB system is cut off, the busbar protection relay RLC places the circuit breaker CBCC in a conductive state to supply power from the common busbar BC to the busbar BA system.

FIG. 2 is a functional block diagram of a busbar protective relay according to an embodiment.
The busbar protective relay RLC includes an input conversion section F1, a fault detection section F2, and a DO unit section F3.
The input conversion unit F1 converts the input current signal and outputs the converted signal to the fault detection unit F2.

The fault detection unit F2 functions as a bus fault detection unit, detects current changes on the common bus BC based on the conversion signal of the input conversion unit F1, detects faults on the common bus BC, and notifies the DO unit unit F3.

The DO unit F3 functions as a first accident response unit, and when an accident on the common bus BC is detected and notified by the accident detection unit F2 using the first route RT1, it sets all circuit breakers on the common bus BC to the cut-off state (open state).

When all the circuit breakers on the common bus BC are in an interrupted state, the input conversion unit F1 converts the input current signal and outputs the converted signal to the fault detection unit F2.
The fault detection section F2 functions as a bus fault detection section, detects a change in current on the common bus BC based on the converted signal of the input conversion section F1, detects a fault on the common bus BC, and notifies the DO unit section F3.

As a result, when an accident on the common bus BC is detected by the accident detection unit F2 using the second route RT2 while all circuit breakers on the common bus BC are in the cut-off state, the DO unit F3 determines that an accident has been detected in the blind spot section, and determines whether the accident was detected on the bus BA or on the bus BB.

The DO unit F3 functions as a second accident response unit, and if it determines that the accident has been detected on either bus BA or bus BB, it shuts off all circuit breakers on the bus where the accident was detected. This completely shuts off the accident current, including the blind spot section.

The DO unit F3 functions as a recovery section, and uses the third route RT3 to reconnect all circuit breakers on the common bus BC connected to the bus on the side where no fault was detected using the second route RT2, to return the bus on the side where no fault was detected to a conductive state, thereby recovering the bus on the side where no fault was detected.

As explained above, according to this embodiment, even if the current transformers (in the case of FIG. 1, current transformer CTC1, current transformer CTA3, current transformer CTC2, and current transformer CTC2) are placed on the secondary side of the circuit breaker to reduce installation space, the effects of blind spots can be eliminated and faults can be cleared by the busbar protection relay.

The operation of the embodiment will now be described in more detail.
[1] Normal Operation First, normal operation (when no abnormality is detected) will be described.
FIG. 3 is a diagram illustrating normal operation.
In FIG. 3, hatched circuit breakers are in a cut-off state (open state), and hatched disconnectors are in an OFF state (open state) (the same applies in the following explanations).

As a result, power from the distribution line LA is supplied to the loads of the bus BA system and the loads of the bus BB system via the disconnector DS, circuit breakers CBA1-3, and multiple disconnectors DS and circuit breakers CBAB.

In parallel with the supply of power from distribution line LA, power from distribution line LB is supplied to the loads of the busbar BA system and the loads of the busbar BB system via disconnector DS, circuit breakers CBB1-3, and multiple disconnectors DS and circuit breakers CBAB.

[2] Operation During Power Transmission Line Inspection FIG. 4 is a process flowchart during power transmission line inspection.
FIG. 5 is an explanatory diagram of a case where a fault on a common bus is detected during an inspection of a power transmission line.

When inspecting a power transmission line, the busbar protection relay RLC first switches the power transmission path (step S11).

For example, in the example of Figure 5, in order to perform a transmission line inspection using the common bus BC and the bus BB of the B system, the two disconnectors DS and the circuit breakers CBA1-3 shown by cross-hatching in Figure 5 are opened, and the transmission path is switched from the state shown in Figure 3 to a state in which the common bus BC and the bus BB are connected, and the inspection is performed.

In FIG. 5, the thick lines indicate the current flow paths.
It is assumed that a fault such as a ground fault occurs at a position PS indicated by a black star in FIG.

Next, the busbar protection relay RLC determines whether an accident such as a ground fault or short circuit has been detected on the common busbar BC based on the output signals of the current transformers CTCC, CTC1, and CTC2 (step S12).

If it is determined in step S12 that an accident on the common bus is detected (step S12; Yes), all circuit breaker call disconnectors on the common bus BC are opened (step S13).

FIG. 6 is an explanatory diagram of a case where a fault is detected in a blind spot section during a power line inspection.
In this embodiment, in order to reduce the installation space for the current transformers, current transformer CTC1 and current transformer CTA4 are arranged on the bus BA side of circuit breaker CBAC, and current transformer CTC2 and current transformer CTB4 are arranged on the bus BB side of circuit breaker CBBC.

In other words, unlike the conventional configuration, one of current transformers CTC1 and CTA4 is arranged on the common bus BC side, which is upstream of circuit breaker CBAC, and the other is arranged on the bus BA side, which is downstream of circuit breaker CBAC. Similarly, one of current transformers CTC2 and CTB4 is arranged on the common bus BC side, which is upstream of circuit breaker CBBC, and the other is arranged on the bus BB side, which is downstream of circuit breaker CBBC.

For this reason, the busbar BA side of the circuit breaker CBAC and the busbar BB side of the circuit breaker CBBC are blind spots for detecting faults on the common busbar, and for example, faults at position PS cannot be detected.

Then, the busbar protection relay RLC functions as the first accident response unit, and opens the circuit breakers CBCC, CBAC, CBBC, CBAB, CBA1-CBA3, CBB1-3, and the two disconnectors DS sandwiching the circuit breaker CBB1-3, which are shown cross-hatched in FIG. 6. In other words, the circuit breakers and disconnectors on the common busbar are opened (step S13).

Then, the busbar protection relay RLC determines whether or not a fault current has still been detected only on the busbar BA side, i.e., whether or not a fault current has been detected in the blind spot section (step S14).

If the judgment in step S14 shows that the fault current is still detected only on the busbar BA side, i.e., if the fault current is detected in the blind spot section (step S14; Yes), the busbar protection relay RLC judges whether the fault current detection point (fault point) is on the busbar BA or on the busbar BB (step S15).

Figure 7 is an explanatory diagram of how to respond to an accident when the fault current detection point (fault point) is on bus bar BA.

In the case of Figure 7, the fault current is detected in current transformer CTC1 and current transformer CTA4, so it is determined that the fault current detection point (fault point) is on bus BA (step S15; BA), and so the busbar protection relay RLC functions as a second fault response unit, and from the state shown in Figure 7, further opens circuit breakers CBA1-3, and opens the circuit breakers and disconnectors on bus BA (step S16).

FIG. 8 is an explanatory diagram of power supply restart.
Next, since the fault current detection point (fault point) is on the bus BA and not on the bus BB side, the bus protection relay RLC functions as a recovery unit and resumes power supply using the common bus BC and bus BB, restoring power supply (step S17), and completing the inspection.

In more detail, the busbar protection relay RLC electrically connects the common busbar BC and the busbar BB by placing the circuit breakers CBCC and CBBC on the common busbar BC side, shown in gray in Figure 8, in a conductive state, and resumes the power supply to the load on the busbar BB side (not shown) via circuit breakers CBB1 to CBB3, completing the inspection after clearing the fault.

On the other hand, if the fault current is detected in current transformer CTC2 and current transformer CTB4 during the judgment in step S15, it is judged that the fault current detection point (fault point) is on bus BB (step S15; BB), so the busbar protection relay RLC functions as a second fault detection unit and further opens circuit breakers CBB1-3 from the state shown in Figure 6, and opens the circuit breakers and disconnectors on bus BB (step S18).

Next, since the fault current detection point (fault point) is on the bus BB and not on the bus BA side, the bus protection relay RLC functions as a recovery unit and resumes power supply using the common bus BC and bus BA, restoring power supply (step S19), and completing the inspection.

More specifically, the busbar protection relay RLC places the circuit breaker CBCC and circuit breaker CBAC on the common busbar BC side in a conductive state, electrically connects the common busbar BC to the busbar BA, and resumes power supply to the load on the busbar BA side (not shown) via circuit breakers CBA1 to CBA3, completing the inspection with the fault cleared.

Also, if it is determined in step S14 that no fault current is detected, i.e., if a fault current is detected only on the common bus BC (step S14; No), the common bus BC is electrically disconnected and power is continued in the normal power supply state shown in Figure 3, i.e., the power supply state from the bus BA and the bus BB, and the inspection is terminated.

Furthermore, if it is determined in step S12 that no fault has been detected on the common bus (step S12; No), this means that a fault current has been detected on either bus BA or bus BB, so the busbar protection relay RLC opens the circuit breakers and disconnectors on the busbar BA or bus BB where the fault (fault current) was detected, and clears the fault (step S21).
Furthermore, the busbar protection relay RLC continues to supply power using the busbars BA and BB in which no fault (fault current) was detected and the common busbar BC (step S22), and ends the inspection.

As described above, according to the embodiment, even if the current transformers (in the case of FIG. 1, current transformer CTC1, current transformer CTA3, current transformer CTC2, and current transformer CTC2) are arranged on the secondary side of the circuit breaker to reduce installation space, the effect of the blind spot section can be eliminated and faults can be cleared by the busbar protection relay.

Here, we will explain why the installation space can be reduced by changing the installation location of the current transformer from the conventional method and installing the circuit breaker (circuit breaker CBAC or circuit breaker CBBC in the example of Figure 1) used at the connection point between the common bus BC and the bus BA or bus BB on the bus BA side or bus BB side.

In the example shown in Figure 1, gas circuit breakers (GCBs) are used for the circuit breakers CBAC and CBBC.

Conventionally, in order to place current transformers (in the example of Figure 1, current transformer CTC1 and current transformer CTA4, or current transformer CTC2 and current transformer CTB4, current detection) on the upstream side (primary side) and downstream side (secondary side) of the GCB (gas circuit breaker), it was necessary to extend the copper pipes for installing the current transformers. This required a large installation space.

In contrast, when current transformers are arranged together only on the downstream side (secondary side) of the GCB (gas circuit breaker) as in the embodiment, they can be arranged, for example, above the installation portion of a disconnector or earthing switch that needs to be installed on the downstream side (secondary side) of the GCB (gas circuit breaker). This allows the copper tubes used for installation to be shorter than in the past, making it possible to reduce the installation space compared to when current transformers are installed on the upstream side (primary side) and downstream side (secondary side) of the GCB (gas circuit breaker).

The busbar protection device of this embodiment is equipped with a control device such as a CPU, a storage device such as a ROM (Read Only Memory) or RAM, a display device such as a display device, and an input device such as an operation button, and has a hardware configuration that uses a normal computer.

The program executed by the busbar protection device of this embodiment is provided as a file in an installable or executable format recorded on a computer-readable recording medium such as a USB memory, a semiconductor memory device such as an SSD (Solid State Drive), or a DVD (Digital Versatile Disk).

The program executed by the busbar protection device of this embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. The program executed by the busbar protection device of this embodiment may be provided or distributed via a network such as the Internet.

The program for the busbar protection device of this embodiment may also be configured to be provided by being pre-installed in a ROM or the like.

The program executed by the busbar protection device of this embodiment has a modular structure including the above-mentioned sections (busbar fault detection section, first fault response section, second fault response section, and recovery section), and in actual hardware, the CPU (processor) reads the program from the above-mentioned storage medium and executes it, loading the above-mentioned sections onto the main memory device, and generating the busbar fault detection section, first fault response section, second fault response section, and recovery section on the main memory device.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

10 Power receiving equipment A1 to A3, A4 Output signal B1 to B3, B4 Output signal BA Bus BB Bus BC Common bus B3 Output signal B4 Output signal C1, C2 Output signal CBA1 to CBA3 Circuit breaker CBB1 to CBB3 Circuit breaker CBA1-3, CBB1-3 Circuit breaker CBAB Circuit breaker CBAC Circuit breaker CBBC Circuit breaker CBCC Circuit breaker CTA1 to CTA3, CTA4 Current transformer CTB1 to CTB3, CTB4 Current transformer CTA-B, CTB-A Current transformer CTA1-3, CTB1-3, Current transformer CTC1, CTC2 Current transformer CTA-1 to CTA3 Current transformer CTB-1 to CTB3 Current transformers CTCC Current transformers DS Disconnector F1 Input conversion section F2 Fault detection section F3 DO unit section LA, LB, LC Distribution line PS Fault location RLA, RLB, RLC Busbar protection relay

Claims (6)

A busbar protection device for protecting busbars of a power receiving facility, the busbar protection device having a plurality of individual busbars constituting a plurality of parallel circuits, a common busbar that can be commonly connected to the plurality of individual busbars, a common current transformer provided on the common busbar side of a common circuit breaker provided at a connection point between the common busbar and the plurality of individual busbars, a plurality of current transformers provided on the individual busbar sides of the common circuit breaker, and a plurality of individual circuit breakers provided on each of the individual busbars and cutting off the corresponding individual busbar when the common circuit breaker is in an interrupted state,
a bus fault detection unit that detects a bus fault based on outputs of the common current transformer and the plurality of current transformers;
a first fault response unit that switches off the common circuit breaker when a bus fault on a common bus is detected by the bus fault detection unit based on an output of the common current transformer;
a second fault response unit that, when a bus fault of a corresponding individual bus is detected based on an output of any one of the plurality of current transformers after the common circuit breaker is tripped, trips the corresponding individual bus;
A busbar protection device equipped with A reset unit that releases the interruption of the common circuit breaker after the second accident response unit has interrupted the individual circuit breaker,
2. The busbar protection device according to claim 1. In a power receiving facility having a plurality of individual busbars constituting a plurality of parallel circuits and a common busbar that can be commonly connected to the plurality of individual busbars,
a common current transformer provided on the common bus side of a common circuit breaker provided at a connection point between the common bus and a plurality of the individual buses;
A plurality of current transformers respectively provided on the individual busbar sides of the common circuit breaker;
a plurality of individual circuit breakers provided at the individual busbars, each of which cuts off the corresponding individual busbar when the common circuit breaker is in an interrupted state;
A busbar protection device that performs the busbar protection,
The busbar protection device includes a busbar fault detection unit that detects a busbar fault based on outputs of the common current transformer and the plurality of current transformers;
a first fault response unit that switches off the common circuit breaker when a bus fault on a common bus is detected by the bus fault detection unit based on an output of the common current transformer;
and a second fault response unit that, when a bus fault of a corresponding individual bus is detected based on an output of any one of the plurality of current transformers after the common circuit breaker is tripped, trips the corresponding individual bus.
Power receiving equipment. The busbar protection device includes a return unit that releases the interruption of the common circuit breaker after the second accident response unit interrupts the individual circuit breaker.
The power receiving equipment according to claim 3. A bus protection method for providing bus protection for power receiving equipment having a plurality of individual busbars constituting a plurality of parallel circuits, a common busbar that can be commonly connected to the plurality of individual busbars, a common current transformer provided on the common busbar side of a common circuit breaker provided at a connection point between the common busbar and the plurality of individual busbars, a plurality of current transformers provided on the individual busbar sides of the common circuit breaker, and a plurality of individual circuit breakers provided on each of the individual busbars and cutting off the corresponding individual busbar when the common circuit breaker is in an interrupted state, comprising:
detecting a bus fault based on outputs of the common current transformer and the plurality of current transformers;
a step of opening the common circuit breaker when a bus fault on a common bus is detected in the step of detecting the bus fault;
a step of shutting off the corresponding individual busbar when a busbar fault of the corresponding individual busbar is detected based on an output of any one of the plurality of current transformers after shutting off the common circuit breaker;
A busbar protection method comprising: and releasing the common circuit breaker after the individual circuit breakers are cut off.
The busbar protection method according to claim 5.

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