Effect of High Fault Currents on Transmission Lines

This chapter provides information on the effects on transmission lines of the increased fault currents which often accompany increased power flows. These effects can include conductor motion and the breakage of conductors and insulators, all of which can be hazardous to personnel. The proper design of transmission lines and equipment will include ensuring that high fault currents do not cause hazards to operating personnel, line workers, and passersby. The chapter deals mainly with suspension insulators although many areas may be relevant to both post and phase-to-phase insulators. The discussion includes conductor motion due to fault currents, calculation of fault currents for horizontally and vertically spaced conductors, and effects of conductor shape and stretch. The electromagnetic forces during a phase-to-phase fault will act to move the conductors apart, placing phase-to-phase spacers in tension. Transmission line spacers are designed to withstand the compressive force on bundled conductors caused by short-circuit forces.