Reducing the effect of sags and momentary interruptions: a total owning cost prospective

Power quality has become a major concern in today´s electric utility industry. This is a result of the fact that modern loads are often sensitive to variations in voltage. Voltage sags and momentary interruptions have proved to be the most costly power quality variation to the consumer. The “cost” of poor power quality depends upon many factors but generally vary from 50 to 400$ per kVA per device year. Numerous mitigation methods have been proposed, e.g., UPSs, ferroresonant transformers, static transfer switches, transformers with electronic tap-changers, and static voltage compensators. Each apparatus presents it´s own set of advantages and disadvantages, commands a different price and entails different operating costs. These technologies are often compared simply on the basis of purchase price alone. This paper present a method of comparing various equipment options by comparing the total owning cost. The total owning cost is found by combining the first cost of the equipment, with the present worth of the operating cost, and addition cost incurred due to limitations of the device. The ratings addressed in this paper are from 20 kVA and 400 kVA