Power factor correction: economic and technical considerations

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University of Dar es Salaam
The dissertation assesses the impact of shunt capacitors for power factor correction and presents a method of evaluating the optimal power factor from economic and technical considerations using automatic switched capacitors and fixed capacitors. The energy consumed is obtained by statistical methods which involve the integration of the square of the measured real time power consumption for the whole working year period. This approach has the advantage of avoiding the use of load factors as it would have required enormous data, collected over a long period, to determine the most appropriate load factor for each of the cases considered. An objective function is derived to determine the amount of savings arising from the application of shunt compensation equipment. The variable, x, which is a function of the compensation factor, k, is introduced to facilitate the determination of the requisite optimal solution. For automatic switched capacitors the solution is derived from a simple expression; however, for fixed capacitors the solution is obtained by application of the Newton-Raphson method. The compensation factor, k, is further used to investigate the optimal technical characteristics. Economic comparison of costs and savings has been made possible by the application of the annual cost method. The study deals with low voltage supply consumers who come under tariff 4 according to the TANESCO categorization. Three firms have been covered in the study; all of them are in Dar es Salaam. Measurements were taken from many other firms; however, the readings could not be used because they experienced many interruptions due to power shedding. The average figures of three typical days are used to derive the annual energy costs and savings. The results have been analyzed and the implications discussed. It is also apparent from the results that higher net savings can be realized with automatic switched capacitors compared to fixed capacitors. The conclusions arising from the results further accentuate the well recognized need for compensation.
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Electric power factor, Tanzania
Maingu, M. I. (1995) Power factor correction: economic and technical considerations, Masters’ dissertation, University of Dar es Salaam. Available at (