JPH0145224Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is based on the main power line from the main transformer to the secondary main circuit breaker in a power distribution system where power is supplied from the primary main circuit breaker to each feeder via the main transformer and the secondary main circuit breaker. The present invention relates to a ground fault protection device equipped with a control mechanism for a ground fault relay device for reliably and quickly providing ground fault protection.

When an accident occurs in a power grid, the fault section must be immediately disconnected to prevent the accident from spreading or expanding, but conventional ground fault protection devices maintain time-limited characteristic coordination with lower-level relay devices. However, in order to prevent malfunctions due to coordination errors, it was necessary to set a considerable time difference between the mutual operation times, and it took a considerable amount of time to protect the main power line from ground faults. , which caused problems with the system's equipment. For example, in a power distribution system that supplies power from a primary main circuit breaker 21 to each feeder F1 to FN via a main transformer 22 and a secondary main circuit breaker 23 as shown in FIG.
4, a GPT (grounded voltage transformer) 25 below the secondary main circuit breaker 23, and a ZCT (zero phase current transformer) below the feeder circuit breakers 26-1 to 26-N of each feeder. The ground fault direction relays 27-1 to 27-N correspond to the ZCT, and the GPT25
is associated with a ground fault overvoltage relay 28, and the voltage detector 24 is associated with a ground fault detection relay 29. For example, when a ground fault occurs at point a of feeder F1, the ZCT, GPT 25 and voltage of that feeder are The detectors 24 are activated, but if the primary main circuit breaker 21 is tripped by this signal, the accident will spread to other healthy feeders, so first the feeder circuit breaker 26-1 is tripped to shut down the feeder. I am trying to separate only F1.
If a ground fault occurs at point b, the GPT 25 and voltage detector 24 will still detect the ground fault even if each feeder circuit breaker trips, so the ground fault overvoltage relay 28 will then Secondary main circuit breaker 23
trip. Then, the voltage detector 24 will not detect the unbalanced voltage of each phase, so the primary main circuit breaker 21 will not be tripped.

If a ground fault occurs at point c, an unbalanced voltage will still be detected by the voltage detector 24 even if the secondary main circuit breaker trips, so the primary main circuit breaker 21 will be tripped only at that time. It is configured to allow

In the conventional system, each relay is given a time-limiting characteristic so that it is tripped from the lower relay, but as mentioned earlier, it is necessary to set a considerable time difference between the mutual activation times to prevent coordination errors and malfunctions. Therefore, there was a problem in that it took a considerable amount of time to protect the main power line from ground faults.

The purpose of the present invention is to solve the problems of the conventional method and to provide reliable and quick ground fault protection for the main power line.

In a power distribution system that supplies power from a primary main circuit breaker to each feeder via a main transformer and a secondary main circuit breaker, each phase of the main circuit breaker is connected to the main power line from the main transformer to the secondary main circuit breaker. a voltage detector for detecting a voltage unbalance of the secondary main circuit breaker, and an opening means for detecting an open state of the secondary main circuit breaker; The present invention relates to a ground fault protection device characterized by comprising a ground fault relay device that opens the primary main circuit breaker when both of the circuit breaker opening signals are output.

The present invention will be explained below based on the embodiment shown in FIG. In this embodiment, each feeder is connected via the primary main circuit breaker 1, main transformer 2, and secondary main circuit breaker
In the distribution system that supplies power to F1 to FN, a voltage detector 4 is installed on the main circuit from the main transformer 2 to the secondary main circuit breaker 3 to detect the voltage of each phase and detect the voltage of each phase that occurs in the event of a ground fault. An unbalanced detection voltage is detected by a ground fault detector. Further, as a means for detecting the open (broken) state of the secondary main circuit breaker 3, the opening/closing signal of the auxiliary switch 5 of the secondary main circuit breaker 3 is used. The ground fault relay device 6 is configured to operate a trip control device 7 that excites the trip coil of the primary main circuit breaker 1 when both the output of the ground fault detector and the switching signal of the auxiliary switch 5 are input. equipped with a circuit. 8 in the figure is GPT,
9-1 to 9-N are feeder breakers, 10-1 to 1
0-N each indicate ZCT.

Now, when a ground fault occurs, the ground fault relay device 6 detects the ground fault based on the signal from the voltage detector 4, but does not output any signal while the secondary main circuit breaker 3 is not opened (broken). If the ground fault is caused by a circuit other than the secondary main circuit breaker 3, the ground fault is eliminated by interrupting the feeder circuit breaker or the secondary main circuit breaker 3. If the ground fault is on the main power line,
The ground fault continues even after the secondary main circuit breaker 3 is shut off, and the auxiliary switch 5 of the secondary main circuit breaker 3 inputs as a signal that the secondary main circuit breaker 3 has opened, so the ground fault relay device 6 is activated and outputs instantaneously or after a set time period to activate the trip control device 7 of the primary main circuit breaker 1 and excite the trip coil to shut off the primary main circuit breaker 1.

In this example, a capacitance type voltage detector is illustrated as a voltage detector for detecting voltage imbalance (ground fault condition) in the main power line, but the present invention is not limited to this, and other types of voltage detectors may be used. Can be used.
Further, although the auxiliary switch of the secondary main circuit breaker is used as a means for detecting the open state of the secondary main circuit breaker, the present invention is not limited to this, and other detection means can be employed.

As mentioned above, according to the present invention, if a ground fault occurs in the main power line, the relay can be activated at any set time after the secondary main circuit breaker has shut off, so the fault area can be closed within a short time. can be disconnected, shortening the duration of the fault, and since opening of the secondary main circuit breaker is a condition for tripping the primary main circuit breaker, it is possible to prevent malfunctions due to miscoordination as in the case of conventional time-limited characteristic coordination. It also has the effect of relieving anxiety.

[Brief explanation of the drawing]

FIG. 1 is a single line diagram showing an embodiment of a ground fault protection device according to the present invention, and FIG. 2 is a single line diagram showing an example of a conventional ground fault protection system. 1...Primary main circuit breaker, 2...Main transformer, 3...
... Secondary main circuit breaker, 4 ... Voltage detector, 5 ... Auxiliary switch, 6 ... Earth fault relay device, 7 ... Trip control device.

Claims (1)

[Scope of utility model registration request] In a power distribution system that supplies power from a primary main circuit breaker to each feeder via a main transformer and a secondary main circuit breaker, voltage fluctuations in each phase of the main power circuit from the main transformer to the secondary main circuit breaker are A voltage detector for detecting balance is provided, and an opening means is provided for detecting an open state of the secondary main circuit breaker, and a ground fault detection signal from the voltage detector and opening of the secondary main circuit breaker by the open detection means are provided. A ground fault protection device comprising a ground fault relay device that opens the primary main circuit breaker when both of the signals are output.