Distribution System Restoration after Prolonged Outages

Most of the customer outages are the results of some problems related to distribution systems. Prolonged outages may cause cold load pickup problems because of the increased penetration of thermostaticallycontrolled devices and the loss of diversity among these devices. Since loads higher than normal may be expected after prolonged outages, restoration problems may occur when there is not enough reserve capacity in the substation. Therefore, distribution system restoration becomes an important issue and it directly affects costumer satisfaction and system reliability level. In the near future, with the increase in automation of distribution systems, the reserve margin of substation capacity will decrease. The decreased margin would require an effective restoration procedure following prolonged outages. Algorithms that will reduce the overall restoration time of distribution systems in case of excessive loads has been studied in the literature and it seems that it will be studied further in the next decays. This review paper intends to give a summary of what has been done and outlines the proposed restoration procedures for cold load pickup for single and for multiple distribution system supplies.