JPH06121454A - Ground fault detector - Google Patents

Abstract

PURPOSE:To remove the cause of a ground fault swiftly by discriminating the cause of the fault from the characteristics of the waveform of the voltage relative to the ground of each phase and the zoro-phase current waveform. CONSTITUTION:Voltage-to-ground detected by a zero-phase transformer ZPT provided on a distribution line and zero-phase current detected by a zero-phase current transformer ZCT are analyzed and calculated by an arithmetic and logic device 2. And, this calculated result and data of ground faults stored in a memory are compared and calculated, and outputted to a display 3. In this way, a ground relay R opens a circuit-breaker CB after a constant time when the ground fault continues, and retrieves the fault section by a fault retriever. Consequently, it becomes possible to detect a precursory phenomenon of the ground fault of the distribution line, and grasp the cause of the ground fault. Accordingly, it becomes possible to remove the cause of the fault swiftly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault accident detection device for determining the cause of a ground fault accident in a distribution line.

[0002]

2. Description of the Related Art A conventional ground fault detector for a distribution line is
As shown in FIG. 4, a distribution transformer T and a circuit breaker CB are provided in the distribution substation. ZCT is a zero-phase current transformer that detects a zero-phase current in the distribution line, and ZPT is a zero-phase transformer that detects a ground voltage. R is a ground fault direction relay that detects a ground fault accident in the distribution line by the outputs of the zero-phase current transformer ZCT and the zero-phase transformer ZPT, and S1 to S6 are section switches that divide the distribution line into a plurality of sections. In the ground fault detection device configured as described above, when a ground fault occurs at point F between the partition switch S5 and the partition switch S6, the zero-phase current transformer ZCT and the zero-phase transformer in the distribution substation. The zero-phase current and the voltage to ground are generated on the secondary side of the device ZPT and are input to the ground fault direction relay R. The ground fault direction relay R starts to be activated by this input, and if the ground fault continues for a certain period of time, it sends an opening command to the circuit breaker CB, and the circuit breaker CB opens. When the circuit breaker opens, the section switches S1 to S6 connected to this circuit breaker open and all the distribution sections are cut off. Next, circuit breaker CB
When the power is turned on to energize the distribution section between the circuit breaker CB and the section switch S1, the accident searcher (not shown) connected to the section switch S1 is activated to operate the distribution section between the circuit breaker CB and the section switch S1. If there is no ground fault accident, the accident searcher will switch to S
Cycle 1 When the section switch S1 is closed, the distribution section between the section switch S1 and the section switch S2 and the section switch S
The distribution section of 1 and the section switch S4 is energized, and the distribution section is sequentially energized to search for a distribution section in which an accident has occurred. Now, when the distribution section of the section switch S5 and the section switch S6 is energized, a ground fault accident occurs at point F of this section, so the ground fault direction relay R operates and the circuit breaker CB opens. . A master station (not shown) installed in the distribution substation and connected to the accident searcher locks the switching of the classification switches S5 and S6, closes the circuit breaker CB again to energize the sound section, and the classification where the accident occurs. Visual inspection of devices, distribution lines, cables, etc. in the distribution section of switches S5 and S6 was conducted to find out the cause of the ground fault.

[0003]

SUMMARY OF THE INVENTION However, the conventional ground fault detection device for a power distribution line manually detects the cause of the ground fault such as a distribution line in a distribution section, a distribution device, a tree near the distribution line, or the like. It took a lot of time and it was difficult to find it because the visual inspection was done by. The present invention has been made to solve the above problems, and an object thereof is to determine the cause of a ground fault accident from the characteristics of each relative ground voltage waveform and zero-phase current waveform.

[0004]

In a distribution system in which a bus of an electric station feeds a plurality of distribution lines, a voltage detector for detecting a ground voltage of the distribution lines and a zero-phase for detecting a zero-phase current of the distribution lines. A current transformer, a storage device that pre-analyzes the ground voltage and zero-phase current of the distribution line when a ground fault occurs in the distribution line, and stratifies and stores the data into the data of each local fault, and a voltage detector provided on the distribution line. And a ground fault accident computing device for detecting the cause of the ground fault by comparing and computing the result of calculating the voltage and zero phase current detected by the zero phase current transformer and the local fault data stored in the storage device. Is provided.

[0005]

Since the cause of the ground fault can be detected by the above means, the power failure can be prevented in advance, and the recovery work can be reduced even if the ground failure involving the power failure should occur.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a ground fault accident detection device of the present invention. The same parts as those in FIG. 4 are designated by the same reference numerals and detailed description thereof will be omitted. 1 is a ground fault accident waveform storage device, which is an insulator of distribution line, creeping discharge such as bushing, strong arc discharge such as internal discharge of pole transformer, arc discharge in pinhole of cable, trees, animals, etc. gradually. Voltage waveform to zero during arc discharge, such as arc discharge when an arc is generated near the power supply section, or when a tree or animal directly contacts the power supply section to cause a short circuit. A storage device 2 that analyzes the phase current in advance and stratifies and stores it in the data of each local fault, and 2 calculates the zero-phase current from the zero-phase current transformer and the ground voltage from the zero-phase voltage transformer provided in the distribution line. A calculation device for comparing and calculating the calculation result and the ground fault accident data stored in the storage device 1 is configured to be output to the display device 3. 2 to 3 are waveform diagrams of the voltage waveform of the distribution line and the zero-phase current waveform in the case of a ground fault, where the vertical axis is the ground voltage and the horizontal axis is the time, and Fig. 2 is the internal discharge of the pole transformer, etc. Is a waveform diagram when a strong arc discharge is generated, (a) is a voltage waveform diagram,
(B) shows a zero-phase current waveform diagram. 3A and 3B are waveform diagrams when a conductor such as a tree or an animal comes into contact with a distribution line. FIG. 3A is a voltage waveform diagram, and FIG. 3B is a zero-phase current waveform diagram. In this way, the voltage and zero-phase current detected from the distribution line in which the ground fault has occurred are analytically calculated and stratified according to the cause of the ground fault and stored in the storage device 1 in advance. In the ground fault detection device configured as described above, the zero-phase transformer ZP provided on the distribution line
The ground voltage detected at T and the zero-phase current detected by the zero-phase current generator ZCT are analyzed and calculated by the arithmetic unit 2, and the result of this difficulty in circle and the ground fault accident data stored in the storage device are compared and calculated. Output to the display device 3. In this way, the ground fault accident continues and the ground fault relay R opens the circuit breaker CB after a certain period of time, and the accident section is searched by the accident search device. In this case, if the zero-phase voltage and zero-phase current of the distribution line are analyzed and detected, the zero-phase voltage waveform and zero-phase current waveform will be the same and the cause of the ground fault can be detected even if the cause of the ground fault is different. It disappears and I do not know in which of the three phases the ground fault occurred.

[0007]

As described above, according to the present invention, it is possible to detect the precursory phenomenon of the ground fault in the distribution line and to know the cause of the ground fault, so that the cause of the accident can be removed quickly. You can do it. Further, even when the ground fault disappears in a short time, the cause of the accident can be determined, and preventive maintenance of the accident can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of a ground fault accident detection device showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a specific implementation of the present invention.

FIG. 3 is a diagram illustrating a ground fault pattern in a distribution line.

FIG. 4 is a block diagram of a conventional ground fault accident section detection device 1 storage device 2 calculation device 3 display device
GPT Zero-phase transformer GCT Zero-phase current R Ground fault relay CB Circuit breaker

Claims (1)

[Claims] 1. In a distribution system for feeding a plurality of distribution lines from a bus of an electric station, a voltage detector for detecting a ground voltage of the distribution lines and a zero-phase current transformer for detecting a zero-phase current of the distribution lines. , A storage device that pre-analyzes the ground voltage and zero-phase current of the distribution line when a ground fault occurs in the distribution line and stratifies and stores them in the data of the local fault, and a voltage detector and zero-phase change provided in the distribution line. The ground fault accident calculator for detecting the cause of the ground fault accident by comparing and calculating the result of calculating the ground voltage and the zero-phase current detected by the current transformer with the local fault data stored in the storage device. A ground fault accident detection device characterized in that