特高压输电线路短路故障时的自由振荡频率分析

Analysis on Natural Frequencies of Ultra-high Voltage Transmission Lines in Short Circuit Fault

特高压输电已成为现代电力系统发展的必然选择。由于它的特殊性和其对系统安全的重要性,找到适合它的保护配置势在必行。特高压输电线路在发生短路故障时会产生自由振荡频率的电流分量,它能为保护提供有效的故障信息。为此,对特高压输电线路在发生各种短路故障时产生的自由振荡频率进行了分析,在不对称故障时利用对称分量法对三相耦合线路进行了解耦,然后通过构建正负序复合网络得到了三相无耦合的自由振荡频率分布,解决了相间短路故障自由振荡频率不易辨识的问题,明确了自由振荡频率可作为有效的故障信息,从而为基于自由振荡频率的暂态保护新原理提供理论支持。鉴于特高压线路都装设有并联电抗器,讨论了它对自由振荡频率的影响。通过PSCAD和MATLAB对实际特高压线路的联合仿真验证,证明了该理论分析的正确性。

The fault current contains the natural frequencies components when the short circuit faults occur in UHV transmission Lines, which can offer effective fault information. Natural frequencies of all short circuit faults was analyzed in this paper, in which the asymmetric fault was decoupled by the symmetric component method, and positive-negative sequence composite network was constructed to get an uncoupled natural frequencies distribution, then natural frequencies identification problem was solved in inter-phase short circuit fault, and that natural frequencies extracted as effective fault information was proved, offering a theoretical basis for the new protection principle based on natural frequencies. Consideration of the shunt reactors were installed in UHV system. The accuracy of PSCAD simulation of practical UHV transmission lines and MATLAB analysis was verified.