注入电流馈线分布特征及其在接地故障检测中的应用

Distribution Model of Injection Current in Feeder and Its Application in Single Phase to Ground Fault Detection

注入法是配网接地故障保护的重要方法之一,然而实际接地故障存在过渡电阻,尤其是高阻接地故障时,传统注入电流分布模型和故障检测方法的有效性受到严重影响。为解决配网单相经高阻接地故障检测的难题,构建了基波注入电流在多馈线配网中的精准分布模型,提出可消除电网分布参数不对称影响的接地故障判定和选线新方法。通过对线路零序电流成分的分解,发现非金属性接地故障下每条线路中均存在注入电流,且分布在每条线路中的比例等于当前工况下该线路零序导纳与系统总导纳的比值,将该比值定义为"分担系数"。针对不同接地方式,刻画出分担系数随过渡电阻变化的轨迹特征,并提出了基于分担系数幅相特征的不对称配电网单相接地故障识别和故障选线方法,理论上消除电网三相分布参数不对称的影响,具有耐受过渡电阻能力强的优势。实际应用中仅需调节一次注入电流并测量被检线路零序电流的变化量,操作简单、易于实现。

Injection method is one of the important methods of distribution network grounding fault protection.However,an actual grounding fault often contains transition resistance,especially in a high resistance grounding fault,the traditional injection current distribution model and fault detection method does not usually work well.In order to solve the problem of single-phase high resistance grounding line protection in asymmetric power grid,a distribution model of zero sequence fundamental current in feeders and a new method for fault line selection in asymmetric power grid are proposed.By decomposing the components of zero sequence current,it is found that in the case of non-metallic grounding fault,the injected current is distributed in each line,and the proportion distributed is equal to the ratio of the zero sequence admittance of the line to the total admittance of the system,which is defined as"sharing coefficient".According to different neutral grounding modes,trajectory distributions of sharing coefficient with the transition resistance were described,and a single-phase grounding fault identification and fault line selection method based on amplitude and phase characteristics of"sharing coefficient"was proposed.Theoretically,this method can eliminate the influence of asymmetry of the three-phase distributed parameters of power grid,and has the advantage of strong resistance tolerance to transition resistance.In practical application,only the injected current needs to be adjusted and the change of zero sequence current of the detected line to be measured,an easy and simple operation.