Comparison between utility sub-station and imitative earthing systems when subjected under lightning response

摘要

A comparison study between the utility substation and imitative earthing systems under lightning response is investigated. The utility sub-station is a non-operational sub-station, and the imitative earthing system is the earthing system that is purposely built to emulate the real earthing systems. However, no equipment is placed or connected to the earthing systems. The imitative earthing system is of a smaller size and is built separately at a different site. Both sites were designed according to the IEEE standard 80. Earth resistance measurements at low magnitude currents and at power frequency were also conducted for both earthing systems based on the IEEE standard 81. When impulse tests were conducted for both configurations, surprisingly the post-ionisation earth resistance of the imitative earthing system under lightning response was found to be similar to those tested under low magnitude currents. However, for the utility sub-station, the earth resistance under lightning response was found to be higher than that designed at steady-state conditions. The results in terms of time delays were also found to be different than that found in literature.