An Overcurrent Protection Relay Based on Local Measurements

Power grid overcurrent relays are used to protect the interphase faults as well as single-phase-to-ground faults. However, these relays do not guarantee protection due to the rapidly increasing short circuits which may be the consequence of demanding more and more power usage by the commercial and residential users. In this paper, a method is presented to improve the functionality of the overcurrent relay. This method is based on locally accessible measurements. It does not require any online-information and communication facilities regarding varying short-circuit levels caused by distributed energy resource infeeds. This method is adaptive and uses a least square algorithm to determine the Thevenin circuit equivalent using local measurements. The proposed method is evaluated, and the results indicate that the Thevenin-equivalent-based method provides an improvement to the relay tripping time.