Advanced Practical Considerations of Fault Current Analysis in Power System Grounding Design

Abstract

Advanced practical considerations for fault current split calculations used in power grounding studies are presented. Scenarios, such as modeling transformers to account for local circulating fault currents, analyzing underground distribution cables, considering tower line faults, and estimating the return current to remote source contributions by means of shield wires, cable sheaths, etc., are analyzed. It is shown that fault current going into the grounding system and the grounding grid safety evaluation can be overestimated or underestimated if the actual situation is not modeled correctly or considered appropriately. Proper examination of various fault scenarios involving circulating current, line fault, and underground cable is also presented. The considerations given in this paper can provide an advanced guideline or reference for power engineers to carry out fault current distribution calculations accurately and therefore avoiding inappropriate designs in grounding studies.