On the role of transformer grounding and low-voltage surge arresters on protecting loads in complex distribution networks

This paper presents a study of overvoltages caused by cloud-to-ground lightning strikes on loads connected to a complex distribution network. The importance of the transformer grounding in reducing load overvoltages is discussed for different lightning events that emphasize either the directly induced voltage component or the surge transfer through the distribution transformer as the main source of overvoltages on the connected loads. A discussion is also presented on the efficiency of low-voltage surge arresters in protecting loads connected to complex low-voltage networks. The obtained results indicate that the effectiveness of improving the transformer grounding and of installing surge arresters at specific points of the low-voltage network can be limited in terms of load protection if a complex network topology is considered.