Using a grounding system equivalent circuit to evaluate transferred lightning surges trough distribution transformers

Grounding in a distribution system is important to reduce the lightning voltage surges that are transferred from medium voltage to the low voltage network through distribution transformers. These overvoltages produce several damages in equipments connected to distribution system and can cause outages of the electrical power supply bringing economic costs to both electric utility and customer. In this paper, is evaluated the impedance of different grounding geometries in the frequency domain; then, this impedance is used to develop an equivalent circuit of the buried grounding configuration and finally, this equivalent circuit and other models for the distribution system components like transformers, surge arresters, etc, are linked in a circuit model to evaluate the transferred voltages through distribution transformers in the alternative transients program (ATP).