新型小电流接地系统选线消谐装置的研制

A novel detector of ground fault and ferro-resonance in ungrounded distribution system

在中性点非直接接地电网中 ,单相接地及由电压互感器 (PT)引起的谐振过电压均是多发性的事故。且由于二者往往均表现为中性点出现位移电压 ,尤其是基波谐振更不易与单相接地区分。这是造成目前小电流接地选线与PT谐振消谐装置均存在误判的主要原因。为克服以上不足 ,本文利用两种故障时的零序电流特征 ,提出了一种小电流接地选线与PT谐振的综合判据 ,据此开发的选线消谐装置在实际运行中也取得了良好效果。

In ungrounded distribution system the single-phase-grounding and the ferro-resonance caused by the PT (Potential Transformer) are of the frequent accidents. In both of the cases above, the shift voltage of neutral point often appears. So one does not differ from the other easily, especially for the fundamental frequency ferro-resonance. It is the primary cause that the present fault-feeder detector and the PT-resonance-eliminator judge wrongly sometimes. To overcome the disadvantage above, a new general criterion, which applies to detect both the fault-feeder and the PT resonance, is presented in this paper. This criterion utilizes the character of the zero-sequence current in the both cases. And the novel detector of ground fault and ferro-resonance, which is developed based on it, works efficiently in practice.