Risk Based Approach to Substation Earthing for SA Power Networks

摘要

SA Power Networks has recently adopted the changes to earthing philosophy detailed in EG-0 Power System Earthing Guide. This method determines the risk of fatality for the most exposed individual based on substation fault level, protection clearing times, fault frequency, and human contact to conductive structures. This is currently done using a fault frequency based on standard values given in EG-0. This paper investigates the methods that SA Power Networks use to record interruptions, and how this information can be used to determine an observed earth fault frequency for use in touch voltage threshold calculations. The last 10 years of fault data for a sample of 39 substations was examined and negligible risk touch voltage thresholds were calculated using clearing times of 0.2 seconds and 1.0 seconds. These thresholds were then compared to those determined using the calculated fault frequency based on line length, and using the IEEE 80 deterministic method previously used by SA Power Networks.