基于优化双稳态去噪的小电流接地系统故障选线方法

Fault Line Selection Method Based on Optimized Bistable Denoising for Non-solid-earthed Network

小电流接地系统发生单相接地故障时,强噪声会造成暂态零序电流故障特征信息难以提取和故障情况随机等问题。为此,提出了一种基于优化双稳态去噪的故障选线方法。首先,在分析噪声对暂态零序电流（TZSC）影响的基础上,将遗传算法和双稳态系统应用到暂态零序电流的去噪中;然后,依据暂态零序电流的峰值将故障情况分为3种模式：强故障模式、中等故障模式与弱故障模式,并获取3类优化双稳态系统;接着,利用这3类优化双稳态系统分别对各线路的暂态零序电流进行去噪,并根据电流峰值最大原则确定暂态特征零序电流（TCZC）;最后,由暂态特征零序电流确定各线路的极性参数,并依据极性参数和极性标准差来建立故障选线判据。仿真结果表明：所提选线方法不受过渡电阻、故障初相角和故障距离等因素影响;同时,在信噪比为-1dB的强高斯白噪声背景下,该方法也能有效滤除噪声;在非母线故障时,该方法能使极性标准差〉0.01,且故障线路的极性参数都小于健全线路;在母线故障时,该方法能使极性标准差〈0.01。研究结果验证了所提故障选线方法的有效性。

To solve the problems that it is difficult to extract fault features in strong noise background and fault conditions randomly occur when signal phase ground faults occur in non-solid-earthed network, we proposed a fault line selection method based on optimized bistable denoising for non-solid-earthed network. Firstly, based on the analysis of the influence of noise on transient zero-sequence current（TZSC）, the genetic algorithm and bistable system were applied in the denoising of TZSC. Secondly, according to the peak value of TZSC, the fault situation was divided into three mode： strong fault mode, medium fault mode, and weak fault mode, and the three optimized bistable systems were obtained. Thirdly, the TZSC for each line was denoised by these three bistable systems, and the transient characteristic zero-sequence current（TCZC） was acquired by the principle of peak current. Finally, the polarity parameters for each lines were determined by the TCZC, and a fault line selection criterion based on the polarity parameter and polarity standard deviation was proposed. The simulation results show that, the proposed method can select fault line exactly in different fault environments including different fault resistances, fault angle, ault distance, and so on, even in the strong noise background of which the signal-to-noise ratio is-1 d B, the proposed method can filter the noise, when the fault is not busbar fault, it can make the polarity standard deviation bigger than 0.01 and the polarity parameter of faulty line is smaller than healthy line; when the fault is busbar fault, it can make the polarity standard deviation smaller than 0.01. The research results verified the effectiveness of the proposed fault line selection method.