Coordination of surge arresters in the low voltage field

The coordination of two surge arresters in the low voltage power system protection field has been thoroughly discussed to date. This subject is especially dealt with in IEC standards. The problem is that nowadays, due to a lot of papers being published and study results apparently conflicting with field experience, it is very difficult for someone who intends to install a surge arrester to know how to coordinate them. This paper explains that one of the major reasons for this situation is that the real characteristics of the arresters needed for performing the coordination study are difficult to obtain except from the manufacturers themselves. It is also shown that between theoretical studies and practical cases, many differences exist which need to be addressed. After listing the relevant parameters based on an analytical study, the paper describes the many tests and computer models which have been developed in order to clarify the situation and give practical guidance. Finally, a new criterion is proposed for arrester coordination which seems more practical than present IEC recommendations.