Possible approaches that facilitate metal oxide surge arrester to turn on under VFTOs

Abstract

There is a general view that MOSAs (Metal oxide surge arresters) are not in a position to offer an effective and consistent protection against VFTOs (Very fast transient overvoltages). Quite predictably, it sheds a poor light on MOSAs. The present sandwiched position of the arrester is mainly due to the combined effect of strong stray and block capacitances existing in EHV (Extra high voltage) network and the characteristic features of the incoming VFTOs. Contrary to this popular view , the experimental and simulation studies detailed in this research work (arrester performance assessment by theoretical method) closely looks at the problem areas and establishes that a successful turnaround in the operation of MOSA under newlineVFTOs is quite achievable. In consonance with the present study procedures, the simulation studies were carried out on a newly developed arrester model using Electromagnetic Transient Program (EMTP). Because, the currently available Metal oxide arrester models are not much useful for investigating arrester behavior against all types of overvoltages, especially for VFTO. Therefore, a new arrester study model has been developed with the inclusion of block and stray capacitances. Necessary calculations of these capacitances were carried out by formulating suitable formulae. A simulation procedure was also formulated to model the arresters of various voltage ratings. As a follow-up, this modified model is validated by the experimental studies conducted on the arresters of different makes and different voltage ratings. newline newline