PES Digital Library

Surge arresters, which are used to protect transformers against overvoltages, are an important part of the power system. Overvoltages occur because of switching operations of nearby circuit breakers or as a result of lightning strokes. The behavior of the surge arrester during an overvoltage occurrence depends on the amplitude and the shape of the surge. Therefore, it is important to have an understanding of the behavior of the surge arrester when it is stressed by overvoltages with different shapes and amplitudes. The application of a simplified model of a surge arrester is presented. The behavior of the arrester based on its measured volt-ampere characteristic is examined according to the ANSI/IEEE C62.11-1993 standard. The residual voltage of the arrester is calculated for three different current impulses: 8/20 μs, 30/60 μs, and an impulse with a 0.5 μs front-of-wave. The application of the model is presented when it is used for protecting a distribution transformer exposed to voltage escalation and to low-frequency surges.