Negative sequence direction longitudinal protective method for very high voltage transmission line

Abstract

Adopting second order RC lowpass filter and half wave difference Fourier algorithm, the invention combines phase module transformation to filter out and obtain negative sequence voltage and current component. Then, using formula obtains action angle of negative sequence direction component. The method possesses enough capability to filter out high-frequency component and attenuate DC component. The negative sequence direction component can capture asymmetry at three-phase short-circuit moment in time and correctly so that the invention shows asymmetric fault, and three phase fault developed from asymmetry. The invention executes correct action within milliseconds at moment fault occurs.

Description

technical field [0001] The invention relates to the field of relay protection for power system transmission lines, in particular to a method for protecting UHV transmission lines. Background technique [0002] Improving the voltage level of the line is an important means to improve the transmission capacity, reduce the network loss and improve the stability of the system operation. UHV transmission lines, that is, transmission lines with a voltage above 1000kV, generally have a long distance and large distributed capacitance. Ensure system stability. In order to limit the overvoltage, the cut-off time of both ends under any fault should not exceed 40-50ms (accurate figure should be calculated by overvoltage). [0003] Russia's 750kV line and 1150kV line adopt two sets of main protection: one is the high frequency protection in the negative sequence direction, and the other is the high frequency protection in the distance high frequency and zero sequence direction. In the ...

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Problems solved by technology

However, due to the relatively slow digital filtering sequence, some literature has questioned whether this method is suitable for computer protection

In the paper "Short Window Algorithm and Fast Power Frequency Directional Components Research" written by Su Bin, Dong Xinzhou, etc. (Source: Tianjin Electric Power Technology-2001(2).-9-16) and written by Li Bin, Li Yongli, He Jiali In his paper "A High-Precision and Fast Filtering Algorithm for Extracting Fundamental Components" (Source: Power System Automation-2006.30(10).-39-43), he proposed an improved narrow bandpass filter and gave a guaranteed delay of The method of assigning the initial value of zero, but in the fast protection that requires a few milliseconds after the fault, the accurate initial value cannot be given by the method in the literature, so the delay of the filter remains to be analyzed

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