Surge-transference characteristics of generator-transformer installations

Progressive increases in generator outputs and in transmission voltages necessitate a re-examination of the relevance of surge transference to the security of the insulation of generators. Simple equivalent circuits representing inductive and capacitive transference are taken as a basis for the analysis of oscillograms of transferred voltages recorded in low-voltage impulse tests on three generator installations. Reasons are found for substantial differences between the measured peak voltages and values calculated from consideration of inductive transference alone. The analysis accounts for the observed asymmetric distributions of voltage between the three phases, and supports the use of a simple lumped-parameter circuit to represent the generator impedance in calculations. From the experimental results, the highest overvoltages to which the three generators could be exposed by surge transference are calculated.