Impact of Lightning Overvoltage on Substation Operating Scenario & Open Busbar End Terminals of AIS Switchyard in EHV Environment

Investigation of lightning overvoltage is an essential part of insulation coordination in AIS substation. To control the lightning overvoltage below specified BIL, surge arrester is used within the substation. The location of surge arrester has a pivotal role in limiting the overvoltage produced by lightning phenomena to below protected equipment BIL throughout the substation to ensure proper insulation coordination. Under different operating scenarios of a substation, LOV produced at different locations of the substation will be different, hence the worst-case scenario shall be used during insulation coordination study. Generally, busbar has higher insulation level BIL, than other equipment in a substation, such as 1550 kVp for busbar & 1425 kVp for other equipment in 400 kV system. However, merely providing higher insulation may not be sufficient for insulation coordination of busbar end terminals. Rather additional surge arresters may also be required to install in some cases. This paper discusses the worst operation scenario of substation for LOV studies and surge arrester requirement at busbar end terminals for LOV control within a 400 kV AIS substation. Results obtained here, in this paper, can be useful for other voltage level also.