小电流接地故障暂态过程的LC谐振机理

对于小电流接地故障,传统基于健全相充电与故障相放电的暂态机理,尚未得到严格理论或实践验证,且仅能反映部分暂态过程。提出一种基于电感—电容(LC)谐振的小电流接地故障暂态机理,即在建立基于线路分布参数小电流接地故障全网模型的基础上,分析各模网络及同模网络内不同检测点阻抗的依频变化(交替呈现容性与感性)特性,给出其间发生LC串联/并联谐振的条件与能量交换规律。研究发现,小电流接地故障暂态过程由同模网络内单条出线、不同线路间的若干组LC并联/串联谐振以及线模和零模网络间LC串联谐振组成,其中频率最小且能量最大的模网络间串联谐振为主谐振,其产生的暂态电压电流含有明确的故障位置信息且易于利用。

LC Resonance Mechanism of Transient Process of Earth Fault in Non-solidly Earthed Network

Traditional transient mechanism based on the charging and discharging of distributed capacitance to earth for single-phase earth faults in non-solidly earthed networks has not yet been analyzed and validated strictly in theory or field. The traditional mechanism only partly reflects the resonance of transient processes and therefore is not accurate or comprehensive enough. A transient mechanism based on LC resonance for single-phase earth fault in non-solidly earthed networks is proposed. Based on the established single-phase earth fault model using distribution line parameters, the impedance characteristics of the frequency-dependency between different modes and different lines in the same mode(the impedance characteristic will alternately appear to be capacitive and inductive)are analyzed. The LC series/parallel resonance conditions and the energy exchange law between capacitive lines and inductive lines are given. A study has found that the transient process of single-phase earth fault can be produced by LC series or parallel resonance in single line, different lines in the same mode, as well as LC series resonance between different modes. The transient current produced by the main resonance(smallest resonance frequency in all the LC series/parallel resonance)contains clear fault location information.