A Semicycle of Ground-Potential Rise

A brief description is presented of why the power utilities need communication during faults. Wire communication channels can supply this need when suitably protected. The maximum groundpotential rise is needed to select protective equipment. How this transient voltage is generated with its wave shape and duration is explained for a single phase-to-ground fault on a power system. The peak occurs at about one-half cycle time at power frequency following a fault at the critical moment, with a magnitude determined by the
X
to
R
ratio. A possibility exists that an even higher voltage results when a phase-to-ground fault changes to a two-phase-to-ground fault after about
\frac{1}{3}
cycle delay.