A novel steady-state-component-based current differential protection scheme for petal-shaped distribution network with inverter-interfaced distributed generators

The petal-shaped distribution network has high power supply reliability. However, the closed-loop operation mode and the access of inverter-interfaced distributed generators (IIDGs) bring great challenges to the protection schemes. The current amplitude differential protection is an effective mean to solve the problem, but the existing criterions rarely consider both sensitivity to high-resistance faults and low requirements for data synchronization. Therefore, the general variation laws of the amplitude difference between current steady-state components at both terminals and the phase difference between current fault components at both terminals are revealed. For external faults, the steady-state-component current amplitude difference is about zero and the fault-component current phase difference is about 180°. For internal faults, either the amplitude difference is large or the phase difference is small. Accordingly, a current differential protection scheme based on the pre-fault and post-fault steady-state current is proposed. The amplitude and phase of current at both terminals of the protected line are required in the proposed scheme, which has low requirements for data synchronization. The simulation results show that the proposed protection scheme is not affected by the fault type, position, resistance and capacity of the IIDGs. It can also be applied to radial distribution networks with IIDGs.