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This paper presents a method for predicting the number of equipment disruptions due to voltage sags in a unit of time based on a concept described in IEC 61000-3-7. The proposed method uses the probabilistic distributions of system disturbance and equipment immunity indices obtained from a unified fuzzy inference engine to represent the disturbance severity and equipment susceptibility of voltage sags. It takes stochastic behavior of service performance into account in the estimation of equipment disruption. The proposed framework is also applicable if other power-quality indices, such as the voltage sag energy index and voltage sag severity index, are adopted. It can be used as an alternative for performing voltage sag coordination and financial analysis. Index Terms--Disturbance level, equipment disruption, fuzzy index, immunity level, power quality (PQ), voltage sag.

Reliability indices have been used for many years to quantify the effects of sustained interruptions on the electric power system. Criteria for representing and reporting the voltage performance are still under development. A proper voltage sag index would be useful for indicating the system performance experienced at different locations. This paper presents an application of fuzzylogic techniques to quantify voltage sags disturbance levels. Retained voltage magnitude and sag duration are the inputs of the proposed system. The output is an index that indicates the relative severity of a voltage sag event. The proposed framework takes network vulnerability, equipment sensitivity, and uncertainties in measuring voltage sags into account, thereby providing meaningful information for both the utility and customers. Fuzzy sets membership functions and inference rules involved in the inference process are described and field data are used to illustrate the analytical resuits. Using the proposed method, site performance indicators can be obtained from the single event indices of all events recorded. The proposed method brings new analytical insights into the assessment of service performance. Index Terms--Disturbance level, fuzzy set, power quality (PQ), single event index, voltage sag, voltage sag index.

Most electricity service interruptions are due to failures in the distribution network. In a competitive market, service quality and reliability have become an essential part of the business. In order to enhance the reliability in the distribution system, a value-based method is proposed in this paper to take load distribution changes into account and search for new locations of feeder sectionalizers such that the customer interruption costs (CIC) can be reduced. Two stages are involved in the search. Using local information, the first stage determines the search direction and, in the second stage, it decides whether a crossover of the load point is beneficial. To avoid being trapped in a local minimum, a mutation technique is also applied to look for the global optimum. Actual feeders were used in the tests and test results have shown that with a proper adjustment of the feeder sectionalizers, service reliability can be improved and the customer outage costs are reduced. Index Terms--Customer interruption cost, distribution reliability, SAIDI, sectionalizer relocation, value-based planning.

Adoption of the IEC flicker standard by IEEE would encourage countries currently using \DeltaV10 flicker standard to consider either updating the \DeltaV10 calculation to make it more suitable for modern day applications, or switching to the IEC standard. In the process of revising the flicker standard, the design of flicker planning level is important. For this purpose, this letter presents comparative statistical analyses of flicker measurements based on present Pst and \DeltaV10 standards. Besides the comparison of synchronous flicker severity indices in 10-min intervals, analyses are also conducted using daily flicker statistical reference values measured at the point of common coupling (PCC) of ac and dc electric arc furnace facilities. [ABSTRACT FROM AUTHOR]