配电线路暂态行波的分析和接地选线研究

ANALYSIS ON TRANSIENT TRAVELING WAVE AND STUDY ON FAULT LINE SELECTION FOR DISTRIBUTION LINES

对于中性点非有效接地的配电系统,当某回线路发生单相接地时,系统的接地电流只有很小的电容电流,并且系统时常运行在不平衡状态,导致利用工频量来选择接地线路很困难。该文以行波理论为基础研究了配电线路单相接地后所产生的暂态电流行波的传播规律和特点,以小波变换为工具,刻划了该行波的接地故障特征,并发现:单相接地瞬间所产生的初始暂态电流行波与接地方式无关,从而为接地选线开辟了新思路。论文最后给出了基于初始电流行波和小波的接地选线判据,并以一个仿真例证明了文中理论推导和所提方法的正确性。该方法为小电流接地选线技术的研究提供了新的思路和出发点,可以构成准确、可靠的接地选线新原理,满足不同的现场CT配置情况。

Because power frequency fault current is very small in amplitude and the system may operate under an asymmetry condition, it is very difficult to correctly identify the faulted line when single phase to ground fault (SFG) occurs in distribution system with non-effectively grounded (NNG) neutral. After analyzing the characteristics of transient traveling waves resulted from SFG in distribution system with wavelet transform, it is found that the initial transient current traveling waves is irrespective of the neural grounding mode when SFG occurs in this paper. According to fact described above, a new faulted line identification algorithm based on transient traveling waves and wavelet transform is proposed. The simulation result demonstrates that the new algorithm is valid. The algorithm is a new idea and is used to design a new principle of fault line selection for NNG system and it can suit for the every case with different CT.