Impulse Voltage Distribution and Transferred Surge in Transformer Winding with Series Reactor – a Case Study

Transformers are critical component within the power system and are often subjected to transient overvoltage due to atmospheric lightening and switching surges. They are subjected to dielectric tests in line with international standards i.e., IEC/IEEE. These transient surges generate oscillatory overvoltage within the winding under impulse and produce transferred overvoltage to untested windings on account of inductive and capacitive coupling [1]. The transferred overvoltage to lower voltage winding can reach remarkably higher values than designed insulation level particularly in case of network transformers with high turns ratio and lead to potential failure. The transferred surge heavily depends on the type of connection of non-tested terminals of untested winding [1] [2]. Usually, the…