Optimal Choice of Fixed and Switched Shunt Capacitors on Radial Distributors by the Method of Local Variations

This paper presents a method of optimally choosing fixed and switched shunt capacitors on radial distribution feeders, considering load growth, growth in load factor and increase in cost of energy. Mathematical models to represent cost saving due to energy loss reduction taking the growth factors into account, cost saving due to release in systam capacities, capacitor cost and voltage rise during off-peek hours, as a function of capacitive current flows in the feeder sections have been formulated. Cost functions have been defined for optimizing the choice of both fixed and switched capacitors. A direct search technique known as the Method of Local Viariations has been employed for solving the resulting discrete variational problem. The problem has also been solved using Dynamic Programming Approach for comparison. The proposed method has been illustrated through some actual cases of radial feeders existing in an Indian distribution network. The results highlighting the influence of the growth factors have also been discussed in this paper.