Metal-Oxide Surge Arrester's Leakage Current Analysis and Thermography

Metal-Oxide arresters are used to protect substation's equipment against surges. Because their constructive properties, a small current, called leakage current, flows through them in normal operation condition. The resistive part of this current is a good indicator of the arrester's degradation state and is also responsible for its heating. This paper discusses the use of thermography and some methods that measure the leakage current for autonomous monitoring of metal-oxide surge arresters. Environment factors that contribute for its surface temperature and, therefore, affect thermography results are evaluated and discussed. In addition, a simple and direct current measurement method is used to obtain the resistive current and show its relation with thermography.