Open-phase fault detection method and device, and automatic change-over switch

Abstract

The invention discloses an open-phase fault detection method which is used for carrying out open-phase fault detection in real time on a three-phase power supply. Aimed at the problem in an existing open-phase fault detection technology that missed detection is easily caused by the influence of a connected load, an existing detection circuit is utilized, a phase difference (or a phase angle difference) between an A phase voltage and a B-C line voltage is detected through an A phase voltage sampling circuit and a B-C line voltage sampling circuit, and according to the inherent change rule of the phase difference under an open-phase condition, a B phase or C open-phase fault is reliably detected; and aimed at the problem that the zero-crossing part of a line voltage sampling signal is a line segment due to a load having a conducting voltage threshold, the phase difference is detected with a middle point of the line segment serving as a zero-crossing moment. The invention further discloses a open-phase fault detection device and an automatic change-over switch. Compared with the prior art, the open-phase fault detection is high in efficiency, the circuit is simple, and the realization cost is low.

Description

technical field [0001] The invention relates to a phase failure detection method, in particular to a phase failure detection method for real-time phase failure detection of a three-phase power supply. 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 vol...

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

In addition, if the output side of the automatic transfer switch is connected to a load with a conduction voltage threshold (that is, the input voltage value reaches a certain level before conducting and working) like some kind of signal indicator light, when the B-phase or C-phase is open, The zero-crossing point in the voltage waveform of the BC line sampled by the voltage sampling circuit is not a point, but will last for a period of time, displayed as a line segment, which also brings new problems for phase failure detection

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