Energy coordination of ZnO varistor based SPDs in surge current due to direct lightning flashes

Surge protective devices (SPDs) play an important role to protect the valuable electrical and electronic equipment against transients originating from lightning. Class I tested SPDs are needed to divert surge currents due to direct lightning flashes. In order to achieve the effective protection of sensitive electrical and electronic systems, coordinated SPD systems should be designed and installed. This paper presents the experimental results obtained from the actual installation conditions of SPDs with the aims to understand the energy sharing of the cascaded Class I and II SPDs and to propose the effective selection and installation methods of SPDs. The residual voltage of each SPD and energy coordination between the upstream Class I tested SPD and the downstream Class tested II SPD were measured using a 10/350 µs current wave.