Zero sequence overcurrent protection method, system and device and computer readable storage medium

Abstract

The invention discloses a zero sequence overcurrent protection method, system and device and a computer readable storage medium. The method can obtain the linear relation between the zero-mode inrushcurrent waveform and the unsaturated core magnetic density and three-phase remanence magnetic density through a zero-mode inrush current analytic equation comprising the saturated mutual inductance ofa transformer, high-voltage side self-leakage resistance, low-voltage side self-leakage resistance, system zero sequence reactance, system voltage, system magnetic density, unsaturated core magneticdensity and remanence magnetic density; can determine the value of the unsaturated core magnetic density in each phase of the three phases through an unsaturated core magnetic density expression. Therefore, after the zero-mode inrush current parameter is substituted into the zero-mode inrush current analytic mode, the zero-mode inrush current waveform can be obtained, thereby achieving the mathematical analysis of the zero-mode inrush current waveform, achieving the analysis of the influence of transformer parameters of different structure types on the magnitude of the zero-mode inrush current. The method can reproduce the waveform when the zero-mode inrush current occurs, and can set the protection criterion of a zero sequence overcurrent protection device, and avoids misoperation of thezero sequence overcurrent protection device.

Description

technical field [0001] The present invention relates to the technical field of electric power system relay protection, in particular to a zero-sequence overcurrent protection method, system, device and computer-readable storage medium. Background technique [0002] The transformer is an important equipment for transferring energy and transforming voltage in the power system. When the transformer is closed with no load or the voltage recovers after the external fault is removed, a large excitation inrush current will appear in the transient process. Free DC component, the transformer core intermittently enters saturation during this process, the exciting inductance decreases sharply, and a large current will appear; in the process of transformer commissioning, there may be cases where the transformer differential protection does not operate and acts as a backup protection The phenomenon of zero-sequence protection action tripping is related to the zero-sequence component caus...

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Problems solved by technology

[0002] The transformer is an important equipment for transferring energy and transforming voltage in the power system. When the transformer is closed with no load or the voltage recovers after the external fault is removed, a large excitation inrush current will appear in the transient process. Free DC component, the transformer core intermittently enters saturation during this process, the exciting inductance decreases sharply, and a large current will appear; in the process of transformer commissioning, there may be cases where the transformer differential protection does not operate and acts as a backup protection The phenomenon of zero-sequence protection action tripping is related to the zero-sequence component caused by transformer excitation inrush current. In the past, this problem was not prominent for a long time and did not attract enough attention

[0003] In recent years, the capacity of the power grid has increased. In order to limit the short-circuit current, new high-impedance transformers have been widely used. However, high-impedance transformers have appeared on the site many times, especially when the high-impedance transformers with built-in high-voltage windings are put into operation. The zero-sequence overcurrent protection of the section switch or even its upper-level line malfunctions, and the protection leapfrogs, seriously endangering the operation safety of the power grid, and the zero-sequence power frequency component that causes the zero-sequence overcurrent protection to malfunction comes from zero-mode inrush current

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