Measurement of the resistive leakage current in surge arresters under artificial rain test and impulse voltage subjection

Surge arresters are installed on transmission and distribution lines and in substations between phase and earth in order to improve the lightning performance and reduce the failure rates. High-energy stresses and housing deterioration are the main factors of degradation and damage of surge arresters. Thus, there is need for testing and monitoring the electrical network's arresters, in order to verify their good condition and their ability to effectively protect the lines. The most common method used, is the measurement of the arresters' total leakage current (with the isolation of the resistive part), which is an indicator of the arrester's condition, since every change, deterioration or damage leads to an increase of the resistive leakage current. In the current work, the total leakage current of two 20 kV ZnO surge arresters without gaps is measured and the resistive component for three different cases (brand new arresters, measurements under artificial rain and measurements after impulse voltage subjection) is computed. The analysis of the produced results can be useful in correct diagnosis of arresters' condition and in more effective schedule maintenance, since any recorded high-resistive currents do not necessarily result arrester's repair or replacement.