Comparison of the safety criteria used for ground grid design at 161/23.9-kV indoor-type substation

This paper compares seven different standards, i.e., IEEE Std. 80, 2000 edition, IEC 60479-1, BS 7354, EA-TS 41-24, CENELEC HD 637 S1, DL/T 621 and ITU-T K.33 used for ground grid design at 161/23.9-kV indoor-type substation in the system of Taiwan Power Company. The calculated results from equations proposed by Sullivan and the Current Distribution Electromagnetic Grounding and Soil structure analysis (CDEGS) software package are also included. The results show IEC 60479-1 gives the lowest limits of tolerable touch and step voltages whereas BS 7354 gives the highest when no chippings on the ground surface are considered. The designed maximum predicted touch voltage obtained from Sullivan’s equation is higher than those obtained from the formulas of BS 7354, EA-TS 41-24, DL/T 621 and CDEGS, the mesh voltage is higher than those from IEEE Std. 80, 2000 edition and CDEGS.

► We compare seven standards used for ground grid design at an indoor-type substation.
► We calculate the tolerable and maximum predicted voltages based on seven standards.
► We compute the ground resistance and minimum buried conductor length of the system.