基于多分辨形态梯度的超高压输电线路无通信全线速动保护新方法

A New Whole Line Non-Communication Quick-Action Protection Scheme for EHV Transmission Lines Based on Multi-Resolution Morphologic Gradient

由于超高压输电线路母线上的杂散电容对高频信号有很强的过滤作用,在区内外短路故障时保护安装处获得的高频分量的大小有明显不同,文章据此提出一种基于数学形态学的超高压输电线路无通信全线速动保护新方法。该方法利用多分辨形态梯度对故障信号进行形态学分解,提取故障暂态电流信号的谱能量来实现区内外故障的识别。保护判据由选定的2层分解系数的谱能量之比来构成。仿真试验表明,只要母线杂散电容和采样频率满足一定的条件,该方法在各种故障条件下均能准确判断故障,具有很好的选择性,并且有很强的抗过渡电阻能力,对末端短路故障的反应灵敏度更高。

Due to the strong filtration of stray capacitance to high frequency signals, as far as the fault signal obtained at the spot where the protection is installed, the amplitude of high-frequency component of inside-zone fault signal evidently differs from that of outside-zone fault signal. According to this phenomenon, the authors propose a new mathematical morphology based whole line non-communication quick-action protection scheme for UHV transmission lines. In this scheme, the morphologic decomposition of fault signal is performed by multi-resolution morphologic gradient technology to extract the spectrum energy to distinguish inside-zone fault from outside-zone fault. The protection criterion is composed by the ratio of spectrum energies of decomposition coefficients belonging to two specified layers respectively. Simulation results prove that so long as both busbar stray capacitance and sampling frequency satisfy a certain condition, the proposed scheme can judge the fault accurately under various fault conditions. The proposed scheme possesses good selectivity and strong ability of anti-transition resistance, besides, it is more sensitive to the fault occurred at the end of transmission fine.