Zero-sequence current protection method, device and equipment

Abstract

The invention relates to a zero sequence current protection method and device and equipment. The method comprises the steps of starting counting when current second harmonic content of zero sequence current is greater than or equal to second harmonic content at the last moment, and obtaining a current count value according to a preset counting rule; recording the second harmonic content within a preset sampling time period when counting is closed and the current count value is greater than or equal to a default value; and opening zero sequence current protection when the recorded second harmonic content is in a gradual descending trend and any second harmonic content in the second harmonic content in the gradual descending trend is smaller than or equal to a default second harmonic contentsetting value. According to the zero sequence current protection method, an inrush current scene state can be accurately distinguished from an asymmetric fault scene state through multiple judgment,so that misoperation caused by excitation inrush current can be effectively prevented, and normal and stable operation of a power grid is further ensured.

Description

technical field [0001] The present application relates to the technical field of zero-sequence current protection, in particular to a zero-sequence current protection method, device and equipment. Background technique [0002] Zero-sequence current protection is widely used in the backup protection of transformer transmission lines and buses. When an asymmetrical ground fault occurs, the zero-sequence current protection can trip in time to isolate the fault. However, when the transformer is closed with no load, due to the asymmetry of the three-phase inrush currents, zero-sequence inrush currents with different amplitudes will be generated. When the zero-sequence inrush current amplitude is greater than the action threshold of zero-sequence current protection, it may cause protection malfunctions. [0003] Therefore, the current traditional zero-sequence current protection is not fully adapted to today's power grid technology, and will cause malfunction due to zero-sequence ...

AI Technical Summary

Problems solved by technology

However, when the transformer is closed with no load, due to the asymmetry of the three-phase inrush current, zero-sequence inrush currents with different amplitudes will be generated. When the amplitude of the zero-sequence inrush current is greater than the action threshold of the zero-sequence current protection, it may cause protection malfunctions.

[0003] Therefore, the current traditional zero-sequence current protection is not fully adapted to today's power grid technology, and will cause malfunction due to zero-sequence inrush current when the transformer is closed with no load or light load, affecting the normal operation of the power grid

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