Energetic coordination of MOV-based surge protective devices

Surge protective devices (SPDs) in multi stage surge protection systems are classified according to IEC 61643-11 [1] as lightning current arresters (class I), surge arresters (class II) and device protection (class III). Class I-lightning current arresters are mostly based on high performance spark gap technology with an impulse current capability up to I_imp = 100 kA 10/350μs. Class II-surge arresters are mostly based on metal oxide varistors (MOVs) with a surge current capability of several 10kA 8/20μs. More and more also class I-arresters based on MOV-technology are present on the market. The energetic coordination between class I- and class II-arresters is a special challenge if both arresters are based on MOV-technology. A comprehensive investigation on the energetic coordination of class I- and class II-arresters based on MOV-technology is shown in this paper taking lightning current impulses 10/350μs into account. A comparison to spark gap based lightning current arresters shows general requirements for both technologies to reach reliable energetic coordination.