Using Positive Sequence Change Quantity and Zero Sequence Component to Realize Line Single-phase Grounding Fault Voltage Protection Method

Abstract

The invention discloses a method for realizing voltage protection of a single-phase earth fault of a line by using a positive sequence break variable and a zero sequence component. The method comprises the steps of: calculating the direction coefficient by using the fault phase positive sequence break variable and zero sequence current; calculating an equivalent positive sequence voltage break variable at a power transmission line protection setting range; calculating zero sequence voltage at the power transmission line protection setting range; and constituting a voltage protection criterion of the single-phase earth fault of the power transmission line by using the zero sequence voltage at the power transmission line protection setting range, the equivalent positive sequence voltage break variable and the direction coefficient. According to the method, the relay protection of the single-phase earth fault of the power transmission line is realized by using the distribution characteristic of the zero sequence voltage and the positive sequence voltage break variable along the power transmission line, the influence of transition resistance on the protection action performance is eliminated in principle, and the action performance is not affected by the load current and the fault position; and the method is suitable for relay protection in two-cycle time after single-phase earth fault of the power transmission line.

Description

technical field [0001] The invention relates to the technical field of electric power system relay protection, in particular to a method for realizing line single-phase grounding fault voltage protection by using positive sequence mutation and zero sequence components. 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 out...

AI Technical Summary

Problems solved by technology

However, the action performance of impedance distance protection is seriously affected by the transition resistance. The main performance is that 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; if the additional impedance generated by the transition resistance is resistive Capacitance is easy to cause the impedance distance protection action to exceed when there is a fault outside the protection zone of the transmission line

[0004] Over / 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 be ignored.

Under the condition of overload transmission, the transmission 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, which will cause the power grid to expand the scope of power outages, and even cause large load transfers to threaten other transmissions. The normal operation of the line has brought huge potential safety hazards to the safety of the power grid

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