Lightning Overvoltages in Electrical Power System of a Power Plant

This paper analyzes lightning overvoltage spikes in an internal network of a large power plant. The cases considered are direct stroke to the phase conductor of the connected power transmission line and back flashover resulting from the lightning stroke to the transmission tower or shield wire. To investigate the transmitted overvoltages through transformers, high frequency models of the transformers are used. The voltage rise at the secondary side of each connected transformer at different voltage levels in the house load network of the power generation plant is analyzed. Protective measures are compared in order the study how to mitigate the transferred overvoltage at the different house load power system levels and to ensure that the impulse voltage is within the basic insulation level (BIL) of the connected equipment. Simulations using different combinations of protective surge arrestors and protective capacitors are done and recommendations on overvoltage protection are presented.