Recent Experimental Findings on the Single and Multi-Impulse Energy Handling Capability of Metal–Oxide Varistors for Use in High-Voltage Surge Arresters

This contribution discusses different aspects of impulse energy handling capability of metal-oxide (MO) varistors used in high-voltage surge arresters. The investigations were performed on more than 3000 MO varistors of different manufacturers worldwide. It can be confirmed that the single-impulse energy handling capability increases with increasing current density of the energy impact, a finding that was also published earlier but based on a very limited number of test samples. In addition, the impact of the MO varistor diameter is discussed. Thereafter, the differentiation of single and multi-impulse energy handling capability is addressed. Finally, investigations with a repeated energy injection (up to 100 prestresses per MO varistor at time intervals that allow the MO varistors to cool down to ambient temperature) are reported. At none of the investigated repeated energy stresses, any change of the V-I characteristic in the leakage current region was observed that would affect the arrester's overall thermal stability.