The role of a synchronous distributed generator on voltage sags

A fault at a distribution substation is studied to investigate the cause of an extended sag after the fault was cleared. Local distributed generation is often thought to help support the system during a fault and minimize sags. However in this case, the presence of a synchronous generator seemed to lengthen the duration of the sag. The combination of the load on the system and the generator was found to contribute to the extended sag. The primary factor was the reactive power drawn by the load during the fault and recovery along with the reaction of the generator. Simulation studies show that such a response could have been predicted if the generator and load were modeled accurately.