The effect of not reconnecting distributed generation on intentional islanding and the cost of energy not supplied in active distribution networks

Using distributed generation resources (DGR) in distribution networks is increasing due to their many advantages. One of these advantages is that their capacity can be used as back up resources for supplying a portion of the load when the main source of the network is lost. In such cases, the distribution network can be divided into several islands. In each of these islands, the load outage duration and the energy not supplied (ENS) of the network can be decreased, considering its distributed generation capacity. This process affects the network restoration and increases the system's reliability. The most important feature of distributed generation for participation in load restoration is its capability of being islanded. One of the features which is essential for islanded operation of DG, is the self-starting capability of DG. This means that the generation unit is able to start without the need to an external voltage source. In this paper, a new approach based on the Imperialist Competitive Algorithm (ICA), which is a well-known and powerful optimization algorithm, is presented for determining the optimal intentional islands in distribution networks. Then, the effect of not reconnecting distributed generation units on the cost of the energy not supplied and the boundaries of the intentional islands after occurrence of a permanent fault in the network is studied as a sensitivity analysis. The proposed approach is applied on the modified IEEE 33-bus test system with four DGs, and the results are presented.