Overload maloperation-proof transmission line phase-to-phase fault backup protection method

Abstract

The invention relates to an overload maloperation-proof transmission line phase-to-phase fault backup protection method. Firstly, fault voltage between phases, fault currents between the phases and fault negative-sequence currents between the phases at a transmission line protection installation portion are measured; arc equivalent resistance between the phases of the transmission line is calculated; arc voltage between the phases of a transmission line phase-to-phase short-circuited fault point is calculated by means of the arc equivalent resistance and fault negative-sequence currents between the phases of the transmission line; then an amplitude value of the arc voltage between the phases and a rated voltage amplitude value of the transmission line constitute backup protection judgment bases of the transmission line phase-to-phase short-circuited fault. According to the method, characteristics of the amplitude value of the arc voltage between the phases constitute relay protection judgment bases of the transmission line phase-to-phase short-circuited fault, motion performance is not influenced by transition resistance, load currents and the operation mode of a power system, the situation that large power grid current transfer caused by backup protection maloperation on the condition that the transmission line is overloaded leads to power failure of power grids in a large range is avoided, and operation safety and stability of the power grids are improved.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a backup protection method for phase-to-phase faults of an overload anti-maloperation 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 mutation of the working voltage amplitude used in this method only exists in the initial stage of the fault, it cannot be used as a backup protection for high-voltage transmission lines. [0003] Impedance distance protection reflects the fault distance according to the measured impedance to distinguish whether the fault point is inside or outside the protection zone. Impedance distance protect...

AI Technical Summary

Problems solved by technology

In fact, in the power system, in addition to the artificially constructed metallic phase-to-phase short-circuit fault, the transition resistance of the actual phase-to-phase short-circuit fault point is not zero, and the additional impedance generated by the transition resistance will seriously affect the operating 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 phase-to-phase fault in the protection zone; if the additional impedance generated by the transition resistance is resistive and capacitive, it is easy to cause the impedance distance protection to exceed when there is a phase-to-phase fault outside the protection zone

[0005] 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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