Condition Monitoring of Metal-oxide Surge Arresters using Leakage Current Signal Analysis

Online condition assessment of surge arresters is necessary for early detection of problems and subsequent replacement of the device to avoid unplanned downtime and/or damage to the equipment being protected. The most common technique of monitoring and assessing the condition of the arrester is extraction of the resistive component of the leakage current. There are many drawbacks to this method arising from inaccuracies in the model-based approach and deficiencies in the understanding of the leakage current signal. This paper presents leakage current signal analysis (LCSA) as a method of assessing the condition of the surge arrester where the harmonics components of the current signal, extracted using Bayesian spectrum estimation, are used as indicators of degradation. An experimental methodology comprising measurement of the leakage current of arresters undergoing constant-stress accelerated degradation testing is employed. Results indicate that a consistent increase in the DC component of the leakage current signal in the case of degrading samples is the most likely indicator of condition.