某500 kV电容式电压互感器介损异常原因分析

Reason Analysis of Abnormal Dielectric Loss of a 500 kV Capacitor Voltage Transformer

分析某500 kV电容式电压互感器(CVT)介损试验数据异常的原因。通过对CVT介损试验接线方式进行分析,初步判定此次介损异常是由于接线方式错误造成的。进一步对错误接线等效电路进行分析,查找出介损异常原因是中间变一次绕组接地时中间变一次回路的等效阻抗引入试验回路,从而导致测量值比实际值偏大。为了保证测量结果的准确性,在测量CVT介损时,必须将中间变一次绕组接地端打开。

Reasons of abnormal dielectric loss of a 500 kV capacitor voltage transformer(CVT)are analyzed.By analyzing the connection mode of CVT dielectric loss test,it is preliminarily judged that the wrong connection mode caused the abnormal dielectric loss.By further analysis of the equivalent circuit of the wrong connection,it is found that reasons of abnormal dielectric loss are the grounding of the intermediate transformer primary winding and the introduction of the primary circuit equivalent impedance of the intermediate transformer into the test circuit,which caused a larger measured value than the actual value.In order to ensure the accuracy of measurement results,the grounding terminal of the intermediate transformer primary circuit must be opened during the measurement of CVT dielectric loss.