High Phase Order Transmission--A Feasibility Analysis Part II--Overvoltages and Insulation Requirements

High phase order transmission (HPO), the use of more than the conventional three phases, is a unique approach to more efficiently using the overhead transmission rights-of-way. This paper evaluates those areas which impact phase clearances and insulation requirements. Fault overvoltages, overvoltagees due to interphase coupling, switching surges, rate of rise of circuit breaker recovery voltage, and lightning performance are analyzed. Additionally, the effects of wind, ice, fault currents, and phase spacer performance on conductor spacing are considered. Representative conductor spacings and terminal insulation levels are tabulated based on the foregoing analyses.