Stresses of switching overvoltages in MW distribution networks with a high rate of cables and their influences on the selection of surge arresters

Environmental influences and the requirements imposed by the licensing authorities are making it necessary to install medium voltage distribution systems with more and more cables, even in sparsely populated areas. In terms of practical operation of the distribution systems, this poses the questions as to which overvoltages can occur in these systems and how to protect the equipment of the distribution system against such overvoltages. Here, the following calculations are performed with a view to answering these questions: switching on cables and overhead lines and of complete networks; disconnection of cables with restriking; initiation of ground faults; and clearing of system faults by the corresponding circuit breakers. The resultant surge voltages are determined and related to the stresses allowed for the items of equipment involved