Placement of protective devices in distribution system considering uncertainties in loads, temporary and permanent failure rates and repair rates

Distribution system reliability is directly affected by the placement of various types of protective devices at different locations of the distribution system. To reduce the momentary interruptions, fuse-blow scheme is used which in turn increases sustained interruption. Utilities having more concern to the sustained interruptions prefer to use fuse-save scheme over fuse-blow scheme. Different models have been developed to solve the problems incorporating placement of various combinations of protective devices in a distribution network for increasing the profit of the utility. The uncertainties in temporary failure rates, permanent failure rates, repair rates and load data have been considered in the problem formulation using three-point estimate method. A generalised objective function capable of simulating different combinations of the protective devices has also been developed. The formulated problems have been solved for 58 bus and IEEE 123 bus distribution networks using mixed integer non-linear programming optimisation technique. After analysing the test results of the various scenarios for the two test systems, it is concluded that maximum profit for the utility is obtained by using the scenario corresponding to a combination of the four protective devices, namely reclosers, switches, fuse-blow fuses and fuse-save fuses.