Open conductor fault detection method and device for three-phase power source and automatic transfer switch

Abstract

The invention discloses an open conductor fault method for a three-phase power source, belongs to the field of low-voltage electrical technology, and aims to solve the problem that missed detection is caused by a connected load easily when the conventional open conductor fault technology is adopted. According to the method, the phase difference (or called phase angle difference) between an A-phase phase voltage and BC line voltage can be detected through an A-phase phase voltage sampling circuit and a BC line voltage sampling circuit by utilizing the conventional detection circuit, and reliable detection of a phase failure of a B phase or a C phase can be realized according to the inherent change rule of the phase difference. The invention further discloses a three-phase power source phase failure detection device and an automatic transfer switch. Compared with the prior art, the impact of the connected load is avoided, so that detection accuracy rate of a phase failure is high; the circuit is simple; the cost is low.

Description

technical field [0001] The invention relates to a three-phase power supply phase failure detection method and device, and belongs to the technical field of low-voltage electrics. Background technique [0002] The automatic transfer switch has been widely used in the industrial power supply system, and the automatic transfer switch realizes the automatic transfer by detecting the fault state of the three-phase power supply which is normally used. The fault state of the three-phase power supply includes undervoltage, overvoltage, and phase failure. The detection of the phase failure of the three-phase power supply usually adopts the following two methods: one is to judge by detecting the phase voltage of A phase, B phase, and C phase Whether there is a phase failure, when the phase voltage of a certain phase is less than 30% of the rated phase voltage, it is judged as a phase failure; When it is less than 30% of the rated phase voltage or the BC line voltage is less than 30% ...

AI Technical Summary

Problems solved by technology

The first method can accurately judge the phase failure, but the hardware circuit is complicated and the cost is relatively high

The second method can save the hardware sampling circuit of one phase. The circuit is simple and the cost is low. However, since the output side of the automatic transfer switch is generally connected with loads such as voltmeters and power meters, the B-phase on the common or standby incoming line side of the automatic transfer switch Or when phase C is open, the detected line voltage value between phase B and phase C may be greater than 30% of the rated line voltage, which will cause the controller to make a mistake in judging that phase B or C is open, which will seriously affect the safety of the entire power supply system reliability

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