Evaluation of Surge Arrester Performance on Damping the Transient Transferred Overvoltage in Transformer

Transformers are the most important electrical apparatus in substations. It is necessary to protect them against high frequency overvoltages. Surge arresters are applied to protect these electrical apparatus from high transient overvoltages such as lightning and switching surges. In this case, mostly surge arresters are installed between phase to ground, as close as possible to the transformer terminals. However, in some cases only phase to ground surge arresters may not be enough to protect transformers against surges and excessive phase to phase overvoltages. In this paper, the behavior of transformer with different types of vector groups, voltage ratios and transmission line length against fast front transient overvoltages is demonstrated. For this aim, EMTP software is applied for analyzing of high frequency overvoltage effects on transformers. Also, the effect of using phase to phase surge arresters to protect transformer insulation against excessive phase to phase overvoltages is investigated.

Keywords:

Surge Arrester , Transformer , Transferred overvoltage , Transient studies.