Protection scheme for active distribution networks using positive-sequence components

Active distribution network is a new pattern for integrating distributed generators (DGs) and smart loads. It features in flexible topologies, plug-and-play functionalities, and active control and management. These features, however, make the conventional protection schemes ineffective in active distribution networks together with the fault-current limiting of inverter-interfaced DGs. This paper proposes protection schemes using positive-sequence components with the aid of the advanced communication techniques. The directional comparison method uses the positive-sequence current fault components to detect solid or low-resistance faults. The impedance differential method using positive-sequence currents and voltages is presented to clear or alarm medium- and large-impedance faults. Both of the protection methods are immune to the varied fault currents and do not require data synchronization between ends of protected feeders. Simulation on a 0.4-kV active distribution network demonstrates the effectiveness of the proposed protection scheme.