Research on feeder protection strategy of distribution network connected with micro-grid

Traditional power distributed network is transformed from single power supply radial network to more than one power supply loop network, direction of the power flow is changed, Therefore action of right protection cannot be completed in the micro-grid operating in the grid-connecting mode and two kinds of operation mode switching of interconnection and lonely island. The four standard of distribution system protection namely, selectivity, reliability, sensitivity and quick action cannot be effectively meet. In paper, influence on relay protection of the micro-grid is expounded in order to solve the problem of micro power grid relay protection, according to the load sensitivity of feeder circuit, current differential protection module and inverse time over-current protection module are established, the parallel operation protection strategy is designed, the simulation results with the typical micro-grid show that performance of the proposed protection module is more rationality and effectiveness.