Grounding considerations for large kVA pad-mount transformers

Abstract

Utilities in the United States and Canada have done extensive analysis of the ground grid design for substations in order to limit step and touch potentials to safe values; however, few have analyzed the potential hazard and designed grounding systems for pad-mount transformers. Since the kVA size and voltage ratings of pad-mounts have increased and the exterior of these facilities are accessible not only to qualified electric utility workers but also the general public, there is a need to analyze and properly design and construct grounding systems which will render these facilities safe for switching and fault conditions. This paper analyzes and develops the design for several different pad-mount transformer voltages and kVA sizes through 5,000kVA.