Volt-time curves of 24 kV porcelain insulators under non-standard impulse waveshapes

This paper presents an application of novel method in order to assess the characteristic of volt-time curves based on Disruptive Effect Model. The tests were performed on a pin-type, porcelain insulator of 24 kV class. Besides the standard 1.2/50 μs impulse voltage waveshape, four non-standard impulse waveshapes, of both polarities, were adopted in the tests, namely 1.2/4 ms, 1.2/10 ms, 3/10 μs, and 7.5/30 μs. The volt-time characteristics obtained from the tests were compared with those predicted by three different procedures related to the Disruptive Effect Model. The results show that the methods by Darveniza and Vlastos and by Hileman do not predict insulator breakdown for the lower peak voltage levels in some cases. On the other hand, a good agreement was found between theoretical and experimental results for the calculations performed using the method proposed by the authors.