JP2000295764A - Distribution facility circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the unnecessary power interruption of the entire distribution system by an earth accident by making the directions of the earth circuit and an earth detecting directional relay the same, and cutting off a breaker of a timer which has the fastest performance when the earth current enters a breaker for a feeder from a point of the earth accident through a distribution loop circuit. SOLUTION: A line 2 for receiving power is connected to a special high voltage line 1 connected to a power transforming station, then an earth switch 3, a disconnector 4, a breaker 5, and a transformer 6 are connected to step down special high voltage to high to voltage, and then a distribution loop circuit which is a high voltage bus is connected. A grounded transformer for measurement or capacitive voltage detector for grounding 8 is connected to a distribution loop 7, and feeders 10, 11 are also connected to the distribution loop 7. Each of the feeders 10, 11 is provided with a disconnector 12, 13 for a feeder, an earth current detector 14, 15, the grounded transformer for measurement or capacitive earth voltage detector 8, and an earth detecting directional relay 16, 17 which is used in combination with the earth current detector 14, 15. Due to this structure, the reliability of supplying power can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power receiving / distributing apparatus, and more particularly to a power receiving / distributing apparatus for transmitting power from a high-voltage bus to a sub-distribution station. The present invention relates to ground fault protection for distribution equipment circuits employing a loop wiring system.

[0002]

2. Description of the Related Art In general, a high-voltage distribution method in a power receiving and distribution device transmits power from one feeder to one sub-distribution station. As the grounding method, a non-grounding method is generally used.

[0003] The ground fault protection in the non-grounding method is provided with a grounded-type instrument transformer or a capacitor-type ground voltage detector on the high-voltage bus, detects a ground-fault voltage via this, and also provides a ground fault provided in each feeder. A ground fault current is detected by a current detector, and an alarm or a ground fault line is disconnected by combining these with a ground fault detection relay. Further, a ground fault voltage detection relay is provided at a tertiary terminal of the grounding type instrument transformer or a secondary terminal of the capacitor type ground voltage detecting device,
By combining the operation of the ground fault voltage detection relay and the operation of the ground fault detection relay in series, it is distinguished from a healthy line to enhance reliability, and the ground fault line is separated.

In contrast to the above, when the power transmission method from the high voltage bus to the plurality of sub-distribution stations is a loop system, generally, current transformers are provided on the power transmission side and the power receiving side, and combined with a pilot wire relay. Thus, the ground fault point section is determined, and the ground fault point is detected and removed.

[0005] Alternatively, when the power transmission method from the high-voltage bus to the plurality of sub-distribution stations is a loop method, a ground-fault current detector is provided on each of the power receiving and transmitting sides of each sub-distribution station. And collectively send and receive power distribution devices such as central monitoring equipment, send the operating status of each relay to a place where it can be monitored and controlled, determine the fault point based on the positional relationship of the operated relays, and open the interrupting device Signals are sent for protection.

[0006]

When a ground fault occurs in any one of the sub-distribution stations of a power receiving and distribution apparatus that performs loop power distribution from a feeder connected to a high-voltage bus to a plurality of sub-distribution stations, or in a cable, In the combination of the ground fault current detector and the ground fault detection relay, not only the ground fault detection relay of the sub distribution station where the ground fault occurred but also the ground fault detection of the sub There is a problem that the relay is also detected and operated at the same time, the shut-off device is opened, and the sound of the sub-distribution station is also cut off.

Further, when the operation status of the relay is sent to a place where the power receiving and distribution devices including the sub-distribution station such as the central monitoring device can be monitored and controlled collectively, and the fault point is determined, the processing is performed. It takes time and despite the accident,
There is a problem that transmission of the open signal to the shutoff device is delayed.

[0008] Further, in the combination of a current transformer and a pilot wire relay, or in the overall monitoring and control of a power receiving and distribution device including a sub-distribution station, it is an advanced device. A large number of control cables need to be laid in the central monitoring device or the like, and the cost is high. still,
Japanese Patent Application Laid-Open No. H10-112928 is an example of such a technique.

An object of the present invention is to provide a power distribution equipment circuit that prevents unnecessary power failures in all power distribution systems due to a ground fault.

[0010]

In order to achieve this object, a power distribution equipment circuit according to a first aspect of the present invention includes a feeder circuit breaker for distributing power of a main bus to a plurality of power supply circuits, and a breaker for each feeder. A distribution loop circuit in which a plurality of sub-distribution stations are connected between units, and a ground-fault current detection for connecting a first and a second circuit breaker to each sub-distribution station and detecting a ground-fault current flowing through each feeder circuit breaker Connect a directional ground fault detection relay to each breaker and a directional ground fault detection relay that detects the reverse ground fault current, connect a timer to the omnidirectional ground fault detection relay, and connect one The case where the timer operation time is sequentially increased from the one-side feeder breaker to the other-side feeder breaker, and the case where the timer operation time of the other breaker goes from the other-side feeder breaker to the one-side feeder breaker. If you want to quickly When the ground fault current flows from the ground fault location to the one-side feeder breaker and the other-side feeder breaker via the distribution loop circuit, the direction of the ground fault current and the direction of the directional ground fault detection relay are the same. And the circuit breaker of the timer having the fastest operation time is cut off.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, a description will be given of a configuration for ground fault protection of a power distribution equipment circuit according to an embodiment of the present invention.

FIG. 1 is an overall system diagram showing a special high-voltage receiving and high-voltage distribution system according to an embodiment of the present invention, in which power distribution from a feeder to a sub-distribution station is loop distribution, and a grounding system is a non-grounding system. . FIG. 2 is a circuit diagram of a control device used for the power receiving and distribution device according to the present embodiment.

In FIG. 1, a power receiving line 2 is connected to a three-phase extra high voltage line 1 connected to a power substation, and the power receiving line 2 is connected to a grounding switch 3, a disconnecting device 4, and a cutoff. The transformer 5, the transformer 6 and the like are connected, stepped down from an extra high voltage to a high voltage, and connected to a distribution loop circuit 7 which is a high voltage bus.

The distribution loop circuit 7 is connected to a grounding type transformer for a meter or a capacitor type grounding voltage detecting device 8, and also to feeders 10 and 11. Feeders 10 and 11 include feeder breakers 12 and 13, ground fault current detectors 14 and 15, a grounding type instrument transformer or a capacitor type grounding voltage detector 8, and ground fault current detectors 14 and 15. Directional ground fault detecting relays 16 and 17 used in combination with the above. Direction ground fault detection relay 1
6 and 17 operate when the ground fault current i flows from the load L toward the special high voltage line 1. From the feeders 10 and 11, loop power is distributed to the respective sub distribution stations 20, 21 and 22.

In each of the sub distribution stations 20, 21, 22 connected to the distribution loop circuit 7, breakers 30, 32, 34 and circuit breakers 31, 33, 35 are connected in series to the distribution loop circuit 7,
Further, each of the sub-distribution stations 20, 21, 22 includes a ground-type instrument transformer or a capacitor-type ground voltage detector 8, and ground-fault current detectors 40, 41, 42, 4 for detecting a ground-fault current.
3, 44, 45, a ground-type instrument transformer or a capacitor-type ground voltage detector 8, and a ground fault current detector 40.
Ground fault detection relay 5 used in combination with ４５45
0, 51, 52, 53, 54, 55. The direction ground fault detection relays 51, 53, and 55 operate when the ground fault current i flows in the same direction as the direction ground fault detection relay 16, and the direction ground fault detection relays 50, 52, and 54 operate as the direction ground fault detection relays 1.
7 operates when a ground fault current i flows in the same direction as that of FIG.

Each of the directional ground fault detection relays 16, 17, 50 to 55 is a tertiary or secondary ground fault current detector 1 of the ground type instrument transformer or the capacitor type ground voltage detector 8.
4, 15, 40 to 45 are connected to the secondary terminals.
Each of the directional ground fault detection relays 16, 17, 50 to 55 detects a voltage output from the tertiary or secondary of the ground type instrument transformer or the capacitor type ground voltage detector 8,
A current output from the secondary terminals of the ground fault current detectors 14, 15, 40 to 45 is detected to detect a ground fault occurring in the system.

When a ground fault is detected, each of the ground fault detecting relays 16, 17, 50 to 55 shown in FIG.
6A, 17A, 50A, 51A, 52A, 53A, 54
A and 55A are closed respectively.

Control devices 10A, 11A, 20A, 20
B, 21A, 21B, 22A, and 22B are connected to respective directional ground fault detection relays 16, 17, 50 to 55, respectively. In addition, the control device 10A is housed in the feeder 10, the control device 11A is housed in the feeder 11, the control devices 20A and 20B are housed in the sub distribution station 20, and the control devices 21A and 21B are housed in the sub distribution station 21. The control devices 22A and 22B are housed in the sub power distribution station 22.

Referring to FIG. 2, control devices 10A, 11A,
20A, 20B, 21A, 21B, 22A, and 22B will be described.

Control devices 10A, 11A, 20A, 20
B, 21A, 21B, 22A, 22B are A contact points 16A, 1 of each direction ground fault detecting relays 16, 17, 50 to 55.
7A, 50A, 51A, 52A, 53A, 54A, 55
When A is closed, the internal A contacts T1A, T2A,
T3A, T4A, T5A, T6A, T7A, T8A operate in a timed manner, and release commands 12A, 13A, 30
A, 31A, 32A, 33A, 34A, 35A are output, the circuit breaker 12 is operated by an open command 12A, the circuit breaker 13 is operated by 13A, the circuit breaker 30 is operated by 30A, and the circuit breaker 31 is operated by 30A.
Is 31A, and the breaker 32 is 32A.
3 is opened by 33A, breaker 34 is opened by 34A, and breaker 35 is opened by 35A.

Here, A contacts T1A, T2A, T3A,
T4A, T5A, T6A, T7A, T8A are connected to a contact T1.
A operates at a later timing than T4A, T4A operates at a later timing than T6A, T6A operates at a later timing than T8A, and the contact T2A operates at a later timing than T7A, and T7A operates at a later timing than T5A. The control devices 10A, 11A, 20A, 20B, and 21 are operated so that T5A operates at a later timing than T3A.
Timers are provided inside A, 21B, 22A, and 22B.

Next, the control devices 10A, 11A, 20A,
The internal configuration of 20B, 21A, 21B, 22A, 22B will be described.

The control device 10A includes a directional ground fault detection relay 1
6 is provided with an A contact T1A that operates after being delayed for a predetermined time by a delay timer T1 connected to the A contact 16A. The delay timer T1 may be a time-adjustable timer. The set time of the delay timer T1 is related to the timers T4, T6, and T8 provided in the control devices 20B, 21B, and 22B, respectively. T1 is set longer than T4, T4 is longer than T6, and T6 is longer than T6. It is set longer than T8. The set time of the delay timer T1 is, for example, 2 seconds, and the set time of the delay timer T4 is, for example, 1.
The setting time of the delay timer T6 is, for example, 1 second, and the setting time of the delay timer T8 is, for example, 0.5 second.

The control device 20B includes a directional ground fault detection relay 5
An A-contact T4A that operates after being delayed for a predetermined time by a delay timer T4 connected to one A-contact 51A is provided. The delay timer T4 may be a time-adjustable timer. The set time of the delay timer T4 is related to the timers T1, T6, and T8 provided in the control devices 10A, 21B, and 22B, respectively. T1 is set longer than T4, T4 is longer than T6, and T6 is It is set longer than T8. The set time of the delay timer T1 is, for example, 2 seconds, and the set time of the delay timer T4 is, for example, 1.
The setting time of the delay timer T6 is, for example, 1 second, and the setting time of the delay timer T8 is, for example, 0.5 second.

The control device 21B includes a directional ground fault detection relay 5
An A-contact T6A is activated after a predetermined time delay by a delay timer T6 connected to the A-contact 53A of No.3. The delay timer T6 may be a time-adjustable timer. The set time of the delay timer T6 is determined by the timers T1 and T1 provided in the control devices 10A, 20B and 22B, respectively.
In relation to T4 and T8, T1 is settled longer than T4, T4 is set longer than T6, and T6 is settled longer than T8. The set time of the delay timer T1 is, for example, 2 seconds, the set time of the delay timer T4 is, for example, 1.5 seconds, the set time of the delay timer T6 is, for example, 1 second, and the set time of the delay timer T8 is, for example, 0. .5 seconds.

The control device 22B includes a directional ground fault detection relay 5
5 is provided with an A contact T8A that is activated after being delayed for a predetermined time by a delay timer T8 connected to the A contact 55A. The delay timer T8 may be a time-adjustable timer. The set time of the delay timer T8 is
Timer T provided in control devices 10A, 20B, 21B
1, T4, and T6, T1 is set longer than T4, T4 is set longer than T6, and T6 is set longer than T8. The set time of the delay timer T1 is, for example, 2
And the set time of the delay timer T4 is, for example, 1.5
The setting time of the delay timer T6 is, for example, 1 second, and the setting time of the delay timer T8 is, for example, 0.5 second.

The control device 11A includes a directional ground fault detection relay 1
7 is provided with an A-contact T2A that is activated after being delayed for a predetermined time by a delay timer T2 connected to the A-contact 17A. The delay timer T2 may be a time-adjustable timer. The set time of the delay timer T2 is
Timer T provided in control devices 20A, 21A, 22A
3, T5, and T7, T2 is settled longer than T7, T7 is set longer than T5, and T5 is settled longer than T3. The set time of the delay timer T2 is, for example, 2
And the set time of the delay timer T7 is, for example, 1.5.
The setting time of the delay timer T5 is, for example, 1 second, and the setting time of the delay timer T3 is, for example, 0.5 second.

The control device 20A includes a directional ground fault detection relay 5
An A-contact T3A is provided, which is activated after being delayed for a predetermined time by a delay timer T3 connected to the 0-A contact 50A. The delay timer T3 may be a time-adjustable timer. The set time of the delay timer T3 is
Timer T provided in control devices 11A, 21A, 22A
2, T5 and T7, T2 is settled longer than T7, T7 is set longer than T5, and T5 is settled longer than T3. The set time of the delay timer T2 is, for example, 2
And the set time of the delay timer T7 is, for example, 1.5.
The setting time of the delay timer T5 is, for example, 1 second, and the setting time of the delay timer T3 is, for example, 0.5 second.

The control device 21A includes a directional ground fault detection relay 5
An A-contact T5A is activated after a predetermined time delay by a delay timer T5 connected to the second A-contact 52A. The delay timer T5 may be a time-adjustable timer. The set times of the delay timer T5 are the timers T2 and T2 provided in the control devices 11A, 20A and 22A, respectively.
T2 is set longer than T7, T7 is set longer than T5, and T5 is set longer than T3. The set time of the delay timer T2 is, for example, 2 seconds, the set time of the delay timer T7 is, for example, 1.5 seconds, the set time of the delay timer T5 is, for example, 1 second, and the set time of the delay timer T3 is, for example, 0. .5 seconds.

The control device 22A includes a directional ground fault detection relay 5
An A-contact T7A is activated after a predetermined time delay by a delay timer T7 connected to the A-contact 54A of No.4. The delay timer T7 may be a time-adjustable timer. The set time of the delay timer T7 is the timer T2 provided in the control device 11A, 20A, 21A, respectively.
T2 is set longer than T7, T7 is set longer than T5, and T5 is set longer than T3. The set time of the delay timer T2 is, for example, 2 seconds, the set time of the delay timer T7 is, for example, 1.5 seconds, the set time of the delay timer T5 is, for example, 1 second, and the set time of the delay timer T3 is, for example, 0. .5 seconds.

Here, for example, the circuit breakers 12, 13, 30 to 35 connected in series on the loop power distribution circuit are all closed to form a power distribution loop circuit, and the feeders 10, 11 serve as sub-power distribution stations 20, 21, 22, 22, respectively. It is assumed that power is transmitted to To detect a ground fault when power is being transmitted from the feeders 10 and 11 in an open loop, a ground-type instrument transformer or a capacitor-type ground voltage detector 8 and a ground-fault current detector 1
4, 15, 40 to 45 and directional ground fault detecting relays 16, 17, 50 connected to their secondary or tertiary terminals.
At 55, a ground fault is detected.

When the directional ground fault detection relays 16, 17, 50 to 55 operate simultaneously, the A contacts 16A, 17A, 5
0A to 55A are closed, and the control devices 10A, 11A, 20
Timers provided inside A, 20B, 21A, 21B, 22A, and 22B excite. The relationship between the timer setting times is as follows: T1 operates at a timing later than T4, T4 operates at a timing later than T6, T6 operates at a timing later than T8, T2 operates at a timing later than T7, and T7 operates at a timing later than T7.
Is activated at a timing later than T5, and T5 is activated at a timing later than T3. For example, T1 is 2 seconds, T
4 is 1.5 seconds, T6 is 1 second, T8 is 0.5 seconds, T2
Is 2 seconds, T7 is 1.5 seconds, T5 is 1 second, and T3 is 0.5 seconds.

As described above, from one timer T1 to the other timer T2, the operation time of each timer is T
1>T4>T6> T8 in order. In addition, the operation time of each timer increases in the order of T2>T7>T5>T3> T1 from the other timer T2 to the one timer T1.

Now, when a ground fault 60 occurs in the sub-distribution station 22 of the distribution loop circuit 7, the ground fault current flows from the ground fault 60 toward one of the feeder breakers 12 and the other feeder breaker 13. i ₁ and ground fault current i ₂ flow. All of the grounding type instrument transformers or the capacitor type grounding voltage detectors 8 detect the ground fault voltage, and the ground fault current detectors 14, 15,.
The ground fault current i ₁ is detected by 41 and 43.

When the ground fault detecting relays 16, 51, 53 in the same direction as the ground fault current i ₁ operate simultaneously, the A contact 1
6A, A contact 51A, and A contact 53A are closed. Among them, the timer with the fastest operation time is the timer T6. Therefore, the timer T6 is excited, the A contact T6A is closed, the cutoff command 33A is input to the circuit breaker 33, and the circuit breaker 33 is tripped.

On the other hand, since there are only 17 directional ground fault detecting relays in the same direction as the ground fault current i ₂ , when the directional ground fault detecting relay 17 operates, the A contact 17A is closed, and the timer T2 is excited. The A contact T2A is closed and the cutoff command 1
3A is input to the circuit breaker 13, and the circuit breaker 13 is tripped.

As a result, power can be supplied to the loads L1 and L2 without power failure of all the loads L1, L2 and L3. In other words, this allows the ground fault point 60 to be separated, so that the other shutoff commands 31A, 12A
A is not output, power transmission from the feeder 10 is continued,
Unnecessary power outages of the sub distribution stations 20 and 21 can be prevented.

Next, in the power distribution loop circuit 7, which is a main circuit cable connecting between the sub power distribution stations 21 and 22, a ground fault 6
Assume that a 1 has occurred.

When the ground fault accident 61 occurs, the ground fault accident 61
, A ground fault current i ₁ and a ground fault current i ₂ flow toward the feeder breaker 12 and the feeder breaker 13. All of the grounding type instrument transformer or the capacitor type grounding voltage detector 8 detects the ground fault voltage, and the ground fault current detectors 14, 41,
43 detects the ground fault current i ₁ .

The location and fault current i ₁ in the same direction of direction ground fault detection relay 16,51,53 is a simultaneously operating, A contact 1
6A, A contact 51A, and A contact 53A are closed. Among them, the timer with the fastest operation time is the timer T6. Therefore, the timer T6 is excited, the A contact T6A is closed, the cutoff command 33A is input to the circuit breaker 33, and the circuit breaker 33 is tripped.

On the other hand, when the directional ground fault detecting relays 17, 54 in the same direction as the ground fault current i ₂ operate, the A contacts 17A,
The A contact 54A is closed and the timers T2 and T7 are excited. However, the timer T7 operates faster than the timer T2. Therefore, the A contact T7A is closed and the cutoff command 34A is input to the circuit breaker 34. Then, the circuit breaker 34 is tripped.

As a result, power can be supplied to the loads without power failure of all the loads L1, L2, L3. In other words, this allows the ground fault point 61 to be separated, so that the other cutoff commands 31A, 12A, 13A
Is not output, the power transmission from the feeders 10 and 11 is continued, and it is possible to prevent unnecessary power outages of the sub distribution stations 20, 21 and 22.

Further, in the case of the ground fault 62, the ground fault current i ₁
And since the breakers 31 and 32 is tripped by a i _2, without full load L1, L2, L3 is a power failure, it is possible to supply power to full load.

Further, in the case of the ground fault 63, the ground fault current i ₁
And since the circuit breaker 12 and 32 trips by the i _2, it is possible to supply power to a load L2, L3.

Further, as another operation method, for example, the circuit breaker 13 connected in series on the loop power distribution circuit is opened, and the other circuit breakers 12, 30 to 35 are all closed to form a closed loop power distribution circuit. It is assumed that power is transmitted to the sub distribution stations 20, 21 and 22, respectively.

Here, in the case of a ground fault accident 62,
So that if open, a ground fault current i ₂ does not flow, it since breaker 31 is tripped by a ground fault current i _1, sub-power distribution station 20, 21, 22 and the power failure state despite a healthy However, the load L1 does not lose power.

In this case, the ground fault current i ₂ flows when the circuit breaker 13 is turned on by a manual or automatic control device on condition that the directional ground fault relay 51 operates and the circuit breaker 31 trips. Although the circuit breaker 32 trips, it is possible to supply power again to the sub distribution stations 20, 21, 22. In this way, open loop operation is also possible.

[0048]

As described above, according to the present invention, the first
The case where the timer operation time of the circuit breaker of the first embodiment is sequentially increased from the circuit breaker for one side feeder to the circuit breaker for the other side feeder, and the timer operation time of the second circuit breaker is changed from the circuit breaker for the other side feeder to the one side feeder. When the ground fault current flows from the ground fault location to the one-side feeder breaker and the other-side feeder breaker through the distribution loop circuit, Since the direction of the current and the omnidirectional ground fault detection relay are the same, and the breaker of the timer with the fastest operation time is cut off, all the loads L1, L2, L3 do not lose power, Power can be supplied to the load, and the reliability of power supply can be improved.

[Brief description of the drawings]

FIG. 1 is a system circuit diagram illustrating an entire configuration of a power distribution equipment circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a control device for ground fault protection according to FIG. 1;

[Explanation of symbols]

1 ... Special high voltage line, 2 ... Power receiving line, 3 ... Ground switch,
4: disconnector, 5: circuit breaker for feeder, 6: transformer, 7:
Distribution loop circuit, 8: Grounding type instrument transformer or capacitor type grounding voltage detector, 10, 11 ... Feeder, 1
0A, 11A, 20A, 20B, 21A, 21B, 22
A, 22B: Control device, 12, 13: Circuit breaker for feeder, 14, 15, 40 to 45: Ground fault current detector, 1
6, 17, 50 to 55 ... directional ground fault detection relay, 20,
21, 22 ... sub distribution station, 30 to 35 ... breaker.

Continued on the front page (72) Inventor Kazuo Kurita 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Inside the Kokubu Plant of Hitachi, Ltd. (72) Inventor Kazuo Kano 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd. Hitachi, Ltd. Inside the factory (72) Inventor Kenichiro Watanabe 2-15-2 Konan, Minato-ku, Tokyo F-term (reference) 2G014 AA04 AB09 AB33 AC19 5G058 EE06 EF03 EG05 EH01

Claims (1)

[Claims] 1. A feeder circuit breaker for distributing power of a main bus to a plurality of power distribution circuits, a distribution loop circuit having a plurality of sub distribution stations connected between the feeder circuit breakers, and a first and a second distribution circuit for each sub distribution station. Connected to a ground fault current detector that detects the ground fault current flowing through each feeder breaker, and a directional ground fault detector that detects the ground fault current in the opposite direction to the directional ground fault detection relay to each breaker. A case in which a short-circuit detection relay is connected, a timer is connected to the omnidirectional ground-fault detection relay, and the timer operation time of one of the circuit breakers is sequentially shortened from the one-side feeder breaker to the other-side feeder breaker. The timer operation time of the other circuit breaker is set to be gradually increased from the circuit breaker for the other side feeder to the circuit breaker for the one side feeder, so that the ground fault current flows from the ground fault to the one side via the distribution loop circuit. Feeder breaker and the other A power distribution equipment circuit, wherein when flowing to a side feeder circuit breaker, a ground fault current and a direction ground fault detection relay have the same directionality and a timer breaker having the fastest operation time is cut off.