智能电网继电保护研究的进展(一)--故障甄别新原理

Development of relay protection for smart grid(1):new principles of fault distinction

利用故障暂态分量在区内故障时线路两侧功率方向相同、暂态能量大的特点,通过小波变换提取这些特征,实现超高压交流线路超高速保护、超高压母线超高速保护;利用直流输电线路端部的直流滤波器和平波电抗器对高频分量形成的阻抗边界,区内短路时高频分量远大于区外短路,使用高频能量在单端实现超高压直流线路全线超高速保护;利用中性点非直接接地系统单相接地时其暂态零序分量是工频分量几十倍并且不被补偿减小的特点,提取零序电流的高频分量,采用方向比较和幅值比较,实现了单相接地故障选线装置。给出了试验装置可以超高速(5ms内)判别故障性质的试验结果,展现了新的故障甄别原理可以满足智能电网中特高压系统对超高速切除故障的美好前景。

As the fault transient components have same power directions at both line ends and great transient energy during internal line faults., they can thus be extracted by the wavelet ＇transform and applied in the ultra-high-speed protections for EHV transmission line and bus. When the DC filter and smoothing reactor are installed at the ends of DC line to form an impedance boundary of high frequency components, which makes the high frequency components of internal fault signals much greater than those of external ones,the energy of them can thus be used to realize the ultra-high-speed protection for UHVDC transmission line at single end. As the transient zero-sequence component is several ten times larger than the power frequency component and not reduced by the compensation during the single-phase-to-ground fault in a neutral indirectly grounding power system,the high frequency component of zero- sequence current is thus extracted to realize the grounding line selection by comparison of direction and amplitude. Tests show that the fault kind can be determined with ultra-high -speed （within 5 ms） and the new principles of fault distinction can satisfy the demand of EHV system for ultra-high-speed fault removal in smart grid.