A zero sequence protection method, device and medium

Abstract

This application discloses a zero-sequence protection method, device and medium, wherein the method first obtains the rated current of the target equipment and the capacitive current of the target equipment loop to ground, and then when the rated current of the target equipment is small, according to avoiding the target equipment Set the zero-sequence current protection setting value for the capacitive current of the loop to the ground, that is, set it according to the conventional zero-sequence protection setting method; when the rated current of the target device is large, the zero-sequence The setting of the current protection setting can avoid the situation that the zero-sequence protection is easy to trip when the neutral point low-resistance grounding system is not equipped with a special zero-sequence current transformer when the large-capacity motor and transformer are powered, effectively ensuring equipment safety and reducing The labor intensity of the post is conducive to efficient organization of production.

Description

technical field [0001] The present application relates to the technical field of power electronics, in particular to a zero-sequence protection method, device and medium. Background technique [0002] In the modern power system, the 6-35kV distribution network generally adopts the low-current grounding method, that is, the neutral point low-resistance grounding method. When a grounding short circuit occurs in the transmission line, a large zero-sequence current will be generated. The device that uses the zero-sequence current generated when grounding to make the protection operate is called zero-sequence current protection. [0003] At present, grounding protection is mainly achieved by using a special zero-sequence current transformer on the cable line. The zero-sequence current transformer passes through three phase lines. Under normal circumstances, the vector sum of the three-phase lines is zero, and the zero-sequence current The transformer has no zero-sequence current...

AI Technical Summary

Problems solved by technology

However, in the neutral point low-resistance grounding system, sometimes there is no dedicated zero-sequence current transformer, but by connecting phase current transformers on the A, B, and C three-phase lines, the primary current with a large value is passed through A certain transformation ratio is converted into a secondary current with a small value, and then the external circuit (three-phase current superposition) synthesizes the zero-sequence current and sends it to the relay protection device to realize the zero-sequence current protection. Since the phase current transformer has a large current The deviation generated when the motor is started and the transformer is switched on will generate a certain starting current and excitation inrush current. When the large-capacity motor and the transformer circuit are powered, the three-phase deviation is superimposed and the zero-sequence protection action occurs, resulting in power transmission failed

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