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.