Development and Testing of New Equipment for Faulty Phase Earthing Applying RTDS

In neutral isolated MV networks the earth fault arc is typically extinguished by an automatic reclosing function. It causes a short interruption for the feeder in question. The earth fault arc can also be extinguished using shunt circuit-breaker to earth the faulty phase temporarily at the feeding, typically 110/20 kV substation. The functioning of the shunt circuit-breaker does not change phase-to-phase voltages of the MV system. Thereby voltage breaks or dips to customers or DG units can be avoided. The shunt circuit-breaker is used for reducing the harmful short interruptions experienced by the customers and electricity producers connected to MV or LV networks. This paper describes the development of the modern shunt circuit-breaker equipment. The main attention was paid to the development, testing and prototyping of the novel shunt circuit-breaker. The developed algorithm for the faulty phase selection was implemented to the feeder terminal. The prototype equipment including the shunt circuit-breaker, the programmable logic controller and IED was tested applying RTDS (Real Time Digital Simulator) environment. The prototype has also been installed and tested with artificial earth faults in the real network.