An Innovative Method for Re-setting Over-current Relays in Active Radial Distribution System

Integration of Distributed Renewable Generation, into electricity distribution networks can be problematic for existing protection schemes due to the effects on fault current levels. In this paper an intrusive method is used to estimate on-line the Thevenin equivalent networks of upstream and downstream sections of a radial active distribution system. The estimated equivalent networks are then used to calculate the fault currents required for the over-current relays settings. The procedure is applicable to low voltage and medium voltage radial networks. OPAL-RT real time simulations are used to validate the proposed method. The requirements for implementing the developed algorithm are also introduced.