JPS59230418A - Ground-fault detecting protecting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ground fault detection and protection device that detects intermittent ground faults that occur in a three-phase AC electrical circuit such as a power system and safely protects the electrical circuit.

A conventional protection device of this type is shown in FIG.

In Fig. 1, (a) is a system configuration diagram showing an example of installing a protective relay, where 1 is an AC power supply, 2 is a power system, and 6 is a breaker for separating AC power supply 1 from power system 2. ,
5 is a protection relay, and 4 is a voltage transformer (hereinafter referred to as PT-g'') that detects the zero-sequence voltage of the power system 2.
) is a characteristic diagram showing the operating characteristics of the protective relay 5, where the horizontal axis shows the input voltage V of the protective relay 5, and the vertical axis shows the operating time T of the protective relay 5.

The next processing operation will be explained.

Now, in FIG. 1(a), if a ground fault occurs at point A of the power system 2, a ground fault zero-sequence voltage is applied to the protective relay 5 by the voltage transformer 4, and It operates according to the characteristics shown in Fig. 1 and outputs an output signal to issue an alarm or trip the circuit breaker 6 to protect the power system 2. Therefore, in this system, a ground fault occurs as shown in Fig. 1 ( It must last for a sufficient period of time to reach the operating characteristics of the protective relay 5 shown in b).

As mentioned above, conventional protection devices cannot provide adequate detection and protection when ground faults occur intermittently (so-called intermittent ground faults).
Due to the abnormal voltage increase on the healthy phase, there was a possibility that the damage caused by the accident would increase due to the failure.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and when an intermittent ground fault fault occurs in a power system, it detects that the ground fault zero-sequence voltage occurs intermittently. When the integrated value of intermittent ground fault zero-sequence voltage reaches a predetermined value, it is determined that the fault is a dangerous intermittent ground fault, and a predetermined protective output signal is sent, an alarm is displayed, or the power system is isolated from the power source. The purpose of the present invention is to provide a ground fault detection and protection device that provides protection by

DESCRIPTION OF THE PREFERRED EMBODIMENTS A ground fault detection and protection device according to an embodiment of the present invention will be described below with reference to the drawings.

In Figure 2, (a) is a configuration diagram showing an example of application of the earth fault detection protection device to an actual power system, and (
b) is a signal waveform diagram showing the relationship between the ground fault zero-sequence voltage and the pulsed signal of this ground fault zero-sequence voltage when a ground fault occurs at point A of the power system 2 in the same figure (al).

In Fig. 2(a), 1 is an AC power supply, 2 is a power system,
3 disconnects this power system 2 from the AC power supply 1 for 1 degree 41
4 is a voltage transformer for detecting the zero-sequence voltage of the power system 2; 6 is a pulse shaping circuit that shapes the zero-sequence voltage of the power system 2 detected by the voltage transformer 4 into pulses; 7 is this pulse shaping An integrator integrates the voltage signal which has become a pulse output signal in circuit 6, 8 is a voltage setting circuit, and 9 is a comparison circuit which receives each output signal of integrator 7 and voltage setting circuit 8 as input. Furthermore, 10 is a ground fault detection and protection device that integrally includes from the pulse shaping circuit 6 to the comparison circuit 9.

Furthermore, in FIG. 1(b), 11 indicates the ground fault voltage signal V which is generated intermittently through the voltage transformer 4, and 1
2 is a pulse shaping circuit 6 that pulses the ground fault voltage signal 11;
This is the signal waveform of the pulse output signal.

Next, the operation of the device of this embodiment will be explained.

Now, in FIG. 2(a), when a ground fault occurs at point A of the power system 2, the pulse shaping circuit 6 receives a ground fault zero-sequence voltage as shown by the ground fault voltage signal 11 in FIG. 2(b). is inputted via the voltage transformer 4, and a pulse waveform of a pulse output signal 12 as shown in FIG. 2(b) is obtained at the output side of the pulse shaping circuit 6. The integrator 7 integrates this pulse output signal and sends a voltage signal to the output side, which becomes one input signal of the comparator 9. Further, the comparator 9 compares the output signal of the integrator 7 and the set output signal of the voltage setter 8, and when the output signal of the integrator 7 exceeds the output set value of the voltage setter 8, a predetermined comparison output signal is output. emits. In other words, if the intermittent ground fault condition persists, multiple pulse signals will be input to the integrator 7, and the output signal of the integrator 7 will increase faster, and if it exceeds the set value, it is determined that an abnormality has occurred in the system 2. That is why it is done. Display an alarm using this comparison output signal, or
Alternatively, the power system 2 is protected by tripping the breaker 6.

As described above, according to the ground fault detection and protection device of the present invention, the ground fault voltage of an intermittent ground fault occurring in a power system is integrated by an integrator, and the severity of the intermittent ground fault is determined based on the integrated value. Since the power system is determined and protected, it is possible to prevent damage caused by repeated shocks caused by sustained intermittent ground faults that occur in the power system, or the spread of accidents caused by abnormal voltages that occur in healthy phases. It has the following effects, and its industrial and economic value is extremely large.

[Brief explanation of drawings]

Figures 1 (a) and (b) are a system diagram and a characteristic diagram showing the operating characteristics of a conventional earth fault protection device, respectively, and Figure 2 (
Fig. 2(a) is a system configuration diagram showing the application of the earth fault detection and protection device according to an embodiment of the present invention to a power system, and Fig. 2(b) shows a signal waveform diagram of each part of the same embodiment. 1... AC power supply, 2... Power system, 6... Breaker, 4... Voltage transformer, 5... Protection relay, 6...
・Pulse shaping circuit, 7... Integrator, 8... Voltage footer, 9... Comparator, 10... Earth fault detection protection device, 1
1.--Intermittent ground fault zero-phase voltage, 12.-- Pulsed signal as above. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (1)

[Claims] A zero-phase voltage detection circuit that detects a zero-phase ground fault voltage in a three-phase AC power system that occurs when a ground fault occurs in the power system; and a pulse shaping circuit that shapes the zero-phase ground fault voltage into a pulse signal sum. , an integrator that integrates the pulse signal with respect to time and outputs an integral output signal, and outputs a set output signal that is a reference value for determining whether or not the ground fault is an intermittent ground fault. 1. A ground fault detection and protection device comprising: a setting device that performs a setting; and a comparator circuit that receives the integral output signal and the setting output signal and sends out a comparison output signal.