Power system single step restoration incorporating cold load pickup aided by distributed generation

When a system is restored after an extended outage, the demand is greater than that was before the outage. The increase in the demand is due to the cold load pickup (CLPU) condition. The attempt to restore such load simultaneously will cause an excessive loading on the network elements in addition to limits violation. For these reasons, step-by-step restoration was suggested by researchers to overcome such problem. However, this way of restoration requires a long time for the complete system to be back to service. In this paper, simultaneous single step restoration of transmission and distribution networks is introduced with the help of distributed generation (DG) units optimally sited and sized by particle swarm optimization (PSO) algorithm. The aim of the proposed DG allocation algorithm is to reduce the distribution substation transformer loss of life due to overloading and to reduce the lost load and hence the additional power demand caused by CLPU. The capacity of the DG required is determined on the basis of additional power demand and the load diversity preserved. The proposed algorithm is applied to the Egyptian 66 kV transmission network in the city of Alexandria including a 33-bus and a 69-bus, 11 kV primary distribution feeders. (C) 2011 Elsevier Ltd. All rights reserved.