Practical Application of EPRI Research for Computing Fault Current Forces

This paper describes a practical application based on the results of a research project performed by EPRI to quantify the behavior of substation switchyard rigid bus and its supporting structure during a fault current event. Two key improvements to standard methodology have been proposed during the last several years compared to the traditional methods: (1) Applying dynamic force time histories to the buses in the structural FEA models, rather than applying static peak force loading; and (2) Performing the short-circuit magnetic force analysis in 3 dimensions rather than 2, which allows the effects of corners and drops to be included. These were formerly largely ignored. The research learnings were applied in conjunction with a condition assessment of a 345 kV switchyard. The new study described in this paper, along with an inspection of the current level of corrosion of the structures, concluded that it was economically feasible to upgrade the switchyard rather than to replace it, with considerable cost savings.