Zero-sequence voltage protection method for single-phase ground fault of transmission line

Abstract

The invention discloses a zero-sequence voltage protection method for single-phase grounding faults of a power transmission line. The method includes firstly, respectively computing equivalent zero-sequence voltage of a power transmission line protection setting range and voltage of the power transmission line protection setting range by the aid of zero-sequence voltage, zero-sequence current, fault-phase negative-sequence voltage and fault-phase negative-sequence current of power transmission line protection mounting positions, secondly, judging whether amplitude of the zero-sequence voltage of the power transmission line protection setting range is higher than that of the equivalent zero-sequence voltage of the power transmission line protection mounting positions or not, and if yes, sending an action tripping signal to trip off breakers at two ends of the power transmission line. A distributed parameter model is used as a physical model, action performance is unaffected by distributed capacitance current, and the method is applicable to any voltage classes, in particular to super-high-voltage / ultra-high-voltage power transmission lines.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a single-phase ground fault zero-sequence voltage protection method of a power transmission line. Background technique [0002] The power frequency variation distance protection constitutes the distance protection by reflecting the sudden change of the working voltage amplitude. This method has the advantages of being less affected by the operation mode of the power system and having a strong ability to resist transition resistance. However, since the sudden change in the working voltage amplitude used in this method only exists in the initial fault stage, it cannot be used as a backup protection for EHV / UHV AC transmission lines. [0003] Impedance distance protection reflects the fault distance according to the measured impedance to distinguish whether the fault point is inside the protection zone or outside the protection zone. Impedance distanc...

AI Technical Summary

Problems solved by technology

Considering the influence of the distributed capacitive current along the transmission line, the relationship between the fault impedance and the fault distance is a hyperbolic tangent function. The amplitude and phase characteristics of the hyperbolic tangent function determine that the impedance relay has poor resistance to transition resistance, and the additional impedance brought by the transition resistance will seriously affect Action performance of impedance relay

EHV / UHV transmission lines transmit large-capacity electric energy and are heavy-duty transmission lines. Heavy-load currents will reduce the action sensitivity of impedance distance protection, and the impact of heavy-load current on the action performance of impedance distance protection cannot be ignored.

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