Performance of surge arrestors under single and multiple lightning impulses

This publication aims on comparing the performance of various types of surge arrestors (metal oxide varistors MOV, surge protective devices SPD and gas discharge tubes GDT) under single and multi-pulse current impulses of waveshape 8/20 μs/μs and 10/350 μs/μs. Lightnings consist in their majority of multiple strokes with a few milli seconds time interval. However, the current standards define tests with several single impulses and time intervals of about a minute. Previous publications present contradictory findings about the effect of multi-pulse lightning. This investigation comes to the conclusion, that failure and performance of MOV and SPD differ substantially from single-to multi-pulse currents. Single impulses of high energy cannot resemble the failures caused by multi-pulse events of even lower energy. MOV of good performance under single pulses show a poor performance under multi-pulse events and vice versa. This is indicated by breakdown of MOV and by change of parameters (e.g. varistor voltage). It is insufficient to simply increase the rating of an SPD for making it more resistant to multipulse events. Failure mechanisms are pre-dominantly immediate explosion due to puncture mode failure or pulse-induced fracture, but also weak mechanical design when complete SPD's were tested. Future research concentrates on systematic investigations of the failure mechanisms and the identification of parameters deciding about multi-pulse capability of MOV.