Maximum Withstand and Types of Damage of Surge Protective Devices under Single and Multi-Pulse Stress

Inhalt:
This paper presents a preliminary, comparative analysis of surge protective devices (SPDs) under single and multi-pulse stress, conducted on a multiple-pulse lightning current generator. Recent research has established that real atmospheric lightning is predominantly characterized by multiple current impulses. However, standardized test impulses typically involve single impulses, adhering to an 'equivalency' type of test. To address this discrepancy, a current impulse generator has been developed, capable of producing up to 10 impulses with a waveshape of 8/20 mus/mus, amplitudes up to 50 kA, and time intervals ranging from 1 to 1000 ms. The multi-pulse current generator has been sponsored by the Deutsche Forschungsgemeinschaft DFG. Initial test results reveal variations in damages and performance of metal-oxide varistors (MOVs) and surge protective devices under the influence of single and multi-pulse currents. No damages were observed for the surges not higher than the specifications declared by the manufacturer. However, MOVs that operate effectively under single pulses may experience diminished performance under multi-pulse conditions, and vice versa. This is observed through both breakdowns of MOVs and alterations in parameters like varistor voltage. Importantly, it is noted that single impulses with high energy levels do not accurately replicate the behaviour caused by multi-pulse events, even when the latter involve lower energy levels. The findings highlight the complexity of the relationship between single and multipulse performance, emphasizing the need for further investigations to deepen our understanding of how surge protective devices respond to different stress conditions.