基于熵值的特高压直流输电线路双端电压保护

Two-terminal Voltage Protection Based on Entropy Analysis for UHVDC Transmission Lines

在分析±800 kV特高压直流输电线路区内外故障过程中发现,由于平波电抗器、直流滤波器和可编程控制滤波器的存在,构成了直流线路的物理边界,并对高频信号具有强烈的衰减作用,因此在保护安装处所提取的区内与区外故障高频信号存在极大差异。利用切比雪夫数字滤波器得到故障电压中600~700 Hz频率段信号,在此基础上提出了一种根据该频率段在故障后1个工频周期内信号的香农熵,实现了区内与区外故障快速准确识别的双端全线快速保护新原理。该方法原理简单、可靠、实用性强、选择性好,能满足特高压直流线路对保护性能的要求。PSCAD/EMTDC仿真结果验证了其可行性和有效性。

In the analysis of faults inside and outside a ±800 kV ultra high voltage direct current（UHVDC）transmission line region,it is found that due to the existence of smoothing reactors,DC filters and programmable logic controller （PLC）filter,the physical boundaries of DC lines are formed,which have strong attenuation for high-frequency signals.Therefore,there is huge difference between the high-frequency fault signals（measured at the position where relay pro？tection is installed）inside and outside the region. Chebyshev digital filter is used to extract the 600~700 Hz signal of breakdown voltage. On this basis,a new principle for a fast protection of two-terminal transmission line is proposed,in which a fast and accurate recognition of the faults inside and outside the transmission line region is realized based on the Shannon entropy of signals in the frequency range and during one power frequency period after fault. This protection principle is simple,reliable,practical,and it has good selectivity,which can meet the protection requirements for UH？VDC line. PSCAD/EMTDC simulation results demonstrate the feasibility and effectiveness of the proposed method.