Safety in AC substation grounding systems under transient conditions: Development of design software

In IEEE80:2000-Guide for Safety in AC Substation Grounding, considers the effect of steady state behaviour of grounding grid. However, due to lightning or any other impulses generated in power system, very high voltages could be built up for a short period of time. The impact of such transient surges on substation grounding systems is studied in this paper. An approach based on Transmission Line method is used to design an equivalent circuit to the substation grounding grid. The developed designs are then simulated for transient behaviour using PSCAD software and appropriate safety parameters are evaluated to find out whether the designs need any modifications. An energy based approach which is more appropriate for transients was used to define threshold of safety. A design software incorporating the findings of the studies was developed as a final outcome.