配电网单相接地保护的研究

为快速识别配电网单相接地故障,断开故障线路并发出故障跳闸信号,仿真分析了配电网单相接地故障时故障线路和正常线路的暂态零序功率的特点,应用小波包精细分析配电网单相接地故障后的暂态零序功率,提取反映故障线路的暂态零序功率特征频带和信号窗长度;以零序电压作为单相接地保护的启动条件,以线路在特征频带和固定时间窗口的暂态零序能量为保护动作判据,构成配电网单相接地的反时限保护。仿真分析表明该单相接地保护动作原理不受短路时刻、接地电弧电阻、线路长度等因素的影响,满足继电保护"四性"要求。

Relay Protection of Single-phase to Ground Fault in Distribution Networks

To quickly distinguish the single-phase grounding faults, to switch off the fault power feeder ,and to send the fault-tripping-operation signal in distribution network, the transient zero-sequence power is analyzed by the wavelet package, which appears when the single-phase to ground fault happens in Neutral Uneffectual Grounded System. The transient zero-sequence electric energy is defined by selecting the characteristic frequency band and signal window length of transient zero-sequence power properly. The principle of inverse time relay protect is presented for single-phase to ground fault in distribution network, in which zero-sequence voltage is regarded as a start condition to work, and the transient zero-sequence electric energy is regarded as the relay protection acting criterion. The simulating analysis shows that the transient zero-sequence power of fault power feeder is different from that of normal power feeder. A great deal of simulation results show that the acting criterion of single-phase grounding relay protection is hardly influenced by the factors such as different short circuit time, arc-resistance and fault distance etc; it can satisfy the demands of the selectivity, speediness, sensitivity and reliability demands of the relay protection.