Methodology for evaluating the cost of a network fault

One of the main tasks of ESKOM, or any other electricity utility, is to provide a reliable electricity supply to its customers at reasonable prices. The more reliable the electricity supply, the higher the price. However, if the system reliability is low, power interruptions and voltage dips tend to occur more often and will eventually result in cost impacts to the utility and to the end customers. The balance between economical and technical considerations is therefore necessary for the utility´s operation. The optimum reliability level will be at the balanced point between the total cost of supply and the benefits to the customers. This paper presents the novel procedure which has been formulated and tested to quantify the customer cost impact, as well as ESKOM´s cost impact, of voltage dips or power interruptions caused by line or substation faults. The proposed methodology involves actual measurements, as well as actual interviews with affected customers. The paper will also document the causes and effects of voltage dips, and the effect of fault current on high voltage power transformers and switchgears. The methodology and results of an actual case study is presented to demonstrate the effectiveness of the proposed procedure. The paper will provide a valuable guide to assist with the quantification of the cost of a network fault. The benefit of identifying these costs would be to enhance project economic evaluations.