Influence of Short-Circuit Currents on HV and EHV Strain Bus Design

Methods are presented to design strain bus for short-circuit currents up to 100 kA rms for new 230 and 500 kV substations and to uprate existing substations. Mechanical, electrical and arc-thermal effects of short-circuit currents on strain-bus systems as they are affected by various design parameters are discussed. These parameters include span length, number and lengths of subspons, bundle-conductor spacing, short-circuit current magnitude and duration. New techniques to reduce short-circuit effects on strain-bus systems for minimum service disruption and cost include the use of polymeric insulated phase-phase spacers, small bundle-conductor spacing, insulation coordination and bay-by-bay analysis of forces on the supporting structures.