Abstract-The increased concern about the financial losses due to voltage sags and interruptions plus the advancements in power electronics technology have led to the innovation of very fast acting intervening equipment that can mitigate such disturbances at the facility entrance. Although significant improvements in the overall power quality can be achieved, however, the high cost of these custom power devices can offset the benefits resulting from their application. The problem therefore, is one of finding a compromised solution that makes technical and financial sense. In this paper, the technical merits of the custom power devices are highlighted, along with their effectiveness in mitigating voltage sags and/or short interruptions. The costs of each application are financially analyzed together with a procedure for the decision maker to compare the payback or the revenue of investment in such devices. A case study of an oil refinery in Alexandria, Egypt is considered to illustrate the proposed procedure.Index Terms-Custom Power Devices, Power Quality, Techno-economic Analysis, Voltage Sags.
I. INTRODUCTIONVoltage sags and short interruptions can be generally described as brief voltage reduction events, followed by restoration of the normal supply conditions. Voltage sags and short interruptions are probably the most serious power quality problems, as they are frequent causes of tripping electrical equipment in industrial installations, leading to costly process shutdowns [1].Custom power devices are a special category of power conditioning equipment, used to protect the entire facility from such voltage disturbances. Custom power devices have to work within parts of a cycle, thanks to the advancements in power electronics technology, such that the load bus will not be affected by the supply disturbance [2].The study work in this paper tries to answer two questions; which custom power device to use and at what cost. The paper proposes a methodology for the decision makers, to Manuscript received February 3, 2010. M. A. El-Gammal is the head of the Electrical Power Engineering Department, Faculty of Engineering, Alexandria University, Alexandria 21544 Egypt (e-mail: gammalmah50@yahoo.com).A. Y. Abou-Ghazala, is the Electrical Power Engineering Department, Faculty of Engineering, Alexandria University, Alexandria 21544 Egypt (e-mail: a.ghazala@electroopower.com).T. I. El-Shennawy is with Alexandria National Refining and Petrochemicals Co. (ANRPC), Alexandria 23111 Egypt (corresponding author, e-mail : tshennawy@yahoo.com, mob.: (+2012) 3926297, Fax.: (+203) 4446785, Phone(+203) 4264161).compare the technical merits and limitations of these devices, along with an economical evaluation of their costs against the financial losses associated with sags and interruptions.
II. VOLTAGE SAGS AND SHORT INTERRUPTIONS
A. DefinitionsThe IEEE Std. 1159-2009 defines voltage sag as: A decrease to between 0.1 and 0.9 pu in rms voltage or current at the power frequency for durations of 0.5 cycle to 1 min. The amplitude of voltage...
