Most recent developments in surge arresters technology and testing

Surge arresters are used in electric power systems to protect the equipment against overvoltage that may arise from lightning events or from internal switching operations. The technology adopted for the construction of such components has evolved during the years. Silicon-carbide type gapped surge arresters has been replaced by most advanced metal-oxide surge arrester without gaps, that can guarantee better performance and a higher degree of reliability. New developments, presently achieved for distribution range, foresee the replacement of the conventional porcelain housing with a polymeric one, allowing to improve the mechanical characteristics and the failure mode behavior. Furthermore special applications for surge arresters, such as protection of gas insulated substations and prevention of lightning faults in transmissions lines, are now taken into consideration by several utilities. The evolution of surge arrester construction technologies and application requires a continuous revision of relevant standards and testing techniques. CESI has been actively involved in testing surge arresters since the 1960s, through the development and setting up of testing facilities and the participation to the major technical and standardization bodies. The paper analyses the most important aspects relevant to surge arrester testing, based on the most recent experience developed in CESI. Particular attention is focused on the short circuit test techniques to address the failure mode and on the ageing test procedures to investigate the long term performance of surge arresters