相电流差突变量选相在混压同塔输电线跨电压故障中的适应性分析

Adaptability Analysis of Phase-selector Based on Sudden-change of Phase-current-difference in Cross-voltage Fault Occurred in Mixed-voltage Transmission Lines

混压同塔四回线易发跨电压故障。对方向或距离纵联保护而言,故障选相非常重要。以弱电强磁的混压同塔四回线系统中单相跨单相接地故障为例,提出了一种将混压同塔四回线路进行完全解耦的复合序网图故障分析方法,并分析在此工况下与实际中所用的简化计算方法下相电流差突变量之间的差异,最后得到相电流差突变量选相适应性与两系统电源电动势相角之间的关系。分析表明,当电源电动势相角之差在不同的范围内时,相电流差突变量选相适应性不同,给出了不同适应性情况下分别对应的相角范围。最后,利用PSCAD软件建立了一个500 k V/220 k V同塔四回线路模型,验证了理论分析的可靠性。

Cross-voltage fault is prone to occur in the mixed-voltage multi-circuit transmission lines system. As to the direction pilot protection and distance pilot protection, phase-selector is important. Taken the single phase to single phase cross-voltage earthed fault in transmission lines with strong-magnetic and weak- electric condition as an example, a composite sequence method that could decoupled the mixed-voltage transmission completely is proposed in this paper. The difference of the sudden-change of phase-current-difference between the proposed phase-selectors and the practically used simplified method is analyzed. Then the relationship between the adaptability of the phase-selector and the electromotive force phase difference of two sources is analyzed. The result shows that the adaptability is depend on the range of the electromotive force phase difference. The ranges of the phase differences for different situations are calculated. Finally, the theoretical analysis is tested in a 500 kV/220 kV four-circuit transmission line model built in PSCAD.