Comprehensive Diagnosis and Analysis of Early Damp Defects On a Single Section of EHV 750kV Arrester

With the extention of the arrester’s running time, there appears the situation that a single section of extrahigh voltage 750kV four series surge arrester may get damp and deteriorated.Once subjected to over-voltage intrusion, a serious situation may even lead to a single section of arrester’s explosion, which will bring a very negative impact to the system over-voltage protection.Through the on-line monitoring of the arrester, it is found that the leakage current of an ultrahigh voltage 750kV arrester became over-limited, we carried out full current and resistive current live detection for the whole arrester and blackout test for single section.We analyzed the data and disintegrated the single section. It is concluded that, for the extrahigh voltage 750kV four series surge arrester, especially for early hidden defects, in terms of live detection, it should be effective to combine the on-line monitoring of arrester, live detection, we should pay attention to data accumulation and development trend.In terms of blackout test, DC leakage test is still the most reliable way to diagnose the arrester defect. Therefore, we should strengthen the on-line monitoring and charge detection data accumulation,and also focus on the development trend and combine with the blackout plan to carry out the DC leakage test actively. In this way we can detect early latent fault of single-stage arrester in time, and provide over-voltage protection correctly.