Protecting machines from line surges

Some of the more important technical problems involved in connecting rotating machines directly to overhead electric power transmission lines are discussed in this paper. Methods are developed for protecting the ground and turn insulations of the armatures of such machines which may be subjected to surge voltages. The ground insulation can be protected by lightning arresters; the turn insulation, by sloping off the incoming surge. Methods are given for determining the maximum allowable rate of rise of voltage at the machine terminals, and the apparatus needed to limit the rate of rise to that value.