Relay protection method for line single-phase ground fault against distributed capacitive current and transition resistance

Abstract

The invention discloses a line single-phase ground fault relay protection method capable of preventing distributed capacitive current and transitional resistance. The method comprises the following steps: a lumped parameter model is utilized for modeling at first; the fault location is calculated; then the physical properties of voltage and current transmission of a transmission line are described by adopting a long-line equation; the obtained fault location is utilized to calculate the offset current of the transmission line; further, the line fault impedance is calculated according to the hyperbolic tangent functional relationship between the voltage drop from the relay location of the transmission line to a single-phase ground fault point and the fault location; and determining whether an action trip signal is sent or not according to the judgment on the amplitude value of the line fault impedance. When the method provided by the invention is adopted for single-phase ground fault relay protection of an ultra / extra-high voltage AC transmission line, the circuit fault impedance from the relay location of the transmission line to the single-phase ground fault point can be accurately calculated, having no reference to the voltage, the distributed capacitive current, the transitional resistance and the load current of the ground fault point, and the action performance can meet the requirements for relay protection selectivity, reliability, sensitivity and quickness.

Description

Technical field [0001] The invention relates to the technical field of power system relay protection, in particular to a line single-phase grounding fault relay protection method against distributed capacitance current and transition resistance. Background technique [0002] Distance protection is less affected by changes in the operation mode and structure of the power system, and can instantly and selectively remove various faults in the transmission line, and has been widely used in the protection of power system transmission lines. The distance protection on the high-voltage transmission line is used as the main protection of the transmission line, and the distance protection on the ultra-high voltage AC transmission line is used as the backup protection of the transmission line. At present, the distance protection widely used in power system transmission lines mainly includes power frequency variable distance protection and impedance distance protection. [0003] The power fr...

AI Technical Summary

Problems solved by technology

Considering the influence of the ground capacitance along the line, the relationship between line fault impedance and fault distance is a hyperbolic tangent function. The hyperbolic tangent function characteristic determines that the impedance relay has poor resistance to transition resistance, and the additional impedance brought by the transition resistance will seriously affect the impedance relay. action performance

The super / extreme voltage AC transmission line transmits large-capacity electric energy, and it is a heavy-duty transmission line. The heavy-load current will reduce the action sensitivity of the impedance distance protection, and the impact of the heavy-load current on the action performance of the impedance distance protection cannot be ignored.

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