A new method to extract the resistive component of the metal oxide surge arrester leakage current

Many studies have been conducted to monitor the degradation of MO arresters. The arresterpsilas leakage current, in particular, the third harmonic component of the resistive leakage current, is known to be directly related to the degree of degradation of the MO arrester. In order to extract the resistive component from the total leakage current, the voltage across the arrester terminals is usually measured as well. Although the measurement of total leakage current in substations or other installations can be easily done by using current shunts or current transformers, the measurement of voltage is relatively difficult if not prohibitive. Apart from the difficult and risky high voltage access for the voltage probe, the voltage measurement in a single phase may suffer from interference from nearby phases resulting in an unclean voltage reference. This paper introduces a new method to extract the resistive current from the total leakage current without the need of the voltage signal. It is referred to as the Modified Shifted Current Method (MSCM). The new modified shifted current method of extracting resistive current component from the metal-oxide surge arrester leakage total current is shown to work well based on the simulated as well as experimental results. The new technique compares very well with the conventional compensation technique, especially for resistive dominated leakage current waveforms. The new technique promises a simplified metal-oxide surge arrester monitoring of resistive leakage current since no additional high voltage transducer, as in commercially available devices, is needed. The consequential benefits are reduced cost and safer working procedure for the maintenance staff.