Abstract
This paper presents a procedure for calculating switching overvoltage on the main circuit breaker of a medium-voltage (MV) cable feeder, to which induction and/or synchronous generators are connected, during a three-phase short circuit. When a fault occurs, the feeder is disconnected by the circuit breaker located at its beginning. After the set operating time of the relay protection, since islanded operation is not permitted, the connected distributed generators will also be disconnected. It is shown that, during the period when the network is disconnected while the generators remain connected, the overvoltage factor reaches values between 2.2 and 2.5, depending on the types of generators and the location of points of common coupling. The individual transient responses of the distribution network and the mentioned types of distributed generators differ significantly. Using the superposition theorem, the calculation of switching overvoltage is demonstrated with elementary computer assistance.