An Investigation of Relay Protections Trips in Medium Voltage Power Grids

The relay protections, used in case of phase-to-phase faults and phase-to-ground faults in medium voltage electrical networks, as types are the overcurrent protections and phase-to-ground protection. The most common electrical power line's faults are the phase-to-ground ones. It is expected that the largest number of relay protections trips will be from phase-to-ground protections. An investigation for the activations and trips from relay protections for a five-year period in a 110/20 kV substation has been made. An analysis of the trips by the relay protections, successful and unsuccessful auto reclose has been made. The power grid operational safety was analyzed based on the obtained results.