一起750 kV变压器出厂试验局放超标现象的分析和处理

Analysis and Treatment of Partial Discharge Exceedin

出厂长时感应耐压带局放测量试验中,某台750 kV变压器在1.5U m√3电压下中压绕组出现局放严重超标的现象。为准确判断局放超标原因并进行处理,采用外部判断、分组定位和解体点检的方法最终确定局放点位于变压器励磁线圈与调压线圈之间,局放原因为绝缘件内部存在气隙。根据原因分析结果,采取更换励磁线圈和调压线圈间所有绝缘件并对器身及装配工艺部件进行全面检查的处理方案,经处理后该变压器出厂试验复试和现场特殊交接试验均顺利通过,局放超标原因分析及处理方案效果得以验证,对后续此类现象分析和处理提供借鉴。

In the factory long-term induction withstand voltage band partial discharge measurement test,a 750 kV power transformer has a phenomenon of serious excessive partial discharge in the medium voltage winding at a voltage of 1.5 Um√3.In order to accurately determine the cause of excessive partial discharge and deal with it,the methods of external judgment,group positioning and disintegration inspection are used to finally determine that the partial discharge point is located between the transformer excitation coil and the voltage regulating coil.According to the results of the cause analysis,a treatment plan was adopted to replace all the insulating parts between the excitation coil and the voltage regulating coil,and to conduct a comprehensive inspection of the body and assembly process components.After the treatment,the re-test of the transformer factory test and the special hand-over test on site were successfully passed.The analysis of the causes of overshoot and the effect of the treatment plan have been verified,providing reference for the subsequent analysis and treatment of such phenomena.