Current protection method for single-phase high-resistance grounding fault of transmission line

Abstract

The invention discloses a current protection method for a power transmission line during a single-phase high-resistance ground fault. The method comprises the steps of firstly measuring an instantaneous current value at a mounting part of a current transformer of the power transmission line at each sampling instant, calculating a fundamental component, a second harmonic component, a third harmonic component and a fifth harmonic component in fault phase current of the power transmission line by processing the sampled instantaneous current values with a fourier algorithm, further calculating an amplitude of a harmonic component in the fault phase current, and then judging that the amplitude of the harmonic component in the fault phase current is greater than a product of a setting coefficient and the amplitude of the fundamental component in the fault phase current. The method realizes relay protection for the single-phase high-resistance ground fault of the power transmission line by single-end amperage, and can act correctly and reliably during the single-phase high-resistance ground fault of the power transmission line, and the acting performances are not influenced by transition resistance, a fault location and the load current.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a single-phase high-resistance grounding fault current protection method for transmission lines. Background technique [0002] The additional impedance generated by the transition resistance will seriously affect the action performance of the impedance distance protection. If the additional impedance generated by the transition resistance is resistive and inductive, it is easy to cause the impedance distance protection to refuse to operate when there is a fault in the protection zone of the transmission line; The distance protection action produces overtaking. [0003] High / super / extreme voltage AC transmission lines are often also heavy-duty transmission lines. Heavy-load currents will cause impedance distance protection to malfunction or refuse to operate. The impact of heavy-load current on the performance of impedance distance protection cannot...

AI Technical Summary

Problems solved by technology

[0002] The additional impedance generated by the transition resistance will seriously affect the action performance of the impedance distance protection

If the additional impedance generated by the transition resistance is resistive and inductive, it is easy to cause the impedance distance protection to refuse to operate when there is a fault in the protection zone of the transmission line; The distance protection action produces overtaking

[0003] High / super / extreme voltage AC transmission lines are often also heavy-duty transmission lines. Heavy-load currents will cause the impedance distance protection to malfunction or refuse to operate. The influence of heavy-load currents on the performance of impedance distance protection cannot be ignored.

Under the condition of overload transmission, the line has no faults. The measured impedance of the traditional distance protection will seriously deviate from the actual measured impedance due to the influence of the overload current, which will easily lead to the misoperation of the traditional distance protection, resulting in the expansion of the power grid blackout range, and even causing a large number of load transfers to threaten the normality of the line. operation, causing a huge security risk to the grid security

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