Applications of microgrids in distribution system service restoration

In the event of a sustained fault in the distribution network, the protective devices trip the appropriate switches to interrupt the fault current and isolate the faulty circuit from the rest of the network. This would limit the propagation of the fault and would improve the availability of supply. However, the customers initially affected by this interruption are not limited to those connected to the faulty circuit; rather, a larger number of customers -for instance those connected to the downstream of the fault location- will be left without electricity. Service restoration algorithms are therefore applied in the distribution management system in order to supply electricity to the customers located in the outage area, while the fault is isolated and the faulty circuit is being repaired. Traditionally, the selection of the restoration sources and the restoration paths is determined only by the capacity margin of the restoration source as well as the rating limits of the equipment along the restoration path. In the absence of a suitable restoration path/source, the customers in the outage area will therefore experience longer interruption periods. This paper investigates the application of autonomous microgrids along the restoration paths and in the outage area in alleviating the congestion level of the circuit and partially releasing its capacity. This would improve system reliability by increasing the success rate of the service restoration solutions.