Evaluation of customer orientated indices and reliability study of electrical feeder system

Aim.Reliability evaluation of a system or component or element is very important in order to predict its availability and other relevant indices. Reliability is the parameter which tells about the availability of the system under proper working conditions for a given period of time. The study of different reliability indices are very important considering the complex and uncertain nature of the power system.Methods.The study uses classical methods of the reliability theory in respect to a system with a constant failure rate consisting of series-connected elements.Conclusions.The paper reviews literature dedicated to the reliability estimation of power supply systems. In particular, the paper examined studies that employed the Markov cut-set approach, the conditional probability approach, distribution systems simulation, probabilistic models, the Monte Carlo method, reliability network equivalent, state transition sampling, inspection repair-based availability optimisation of distribution systems, bootstrapping, fault tree analysis, Bayes networks, peak-valley partition model, demand response model, etc. The authors defined the problem and analysed input data. They showed that, in physical terms, the system configuration will be a series reliability network. Given the above, the system fails even if one component fails, and survives if all of the components survive. It is noted that, when considering the reliability of series systems, the three basic parameters are average failure rate, average annual outage time and average repair time. As the customer orientated indices associated with the research of operational reliability the system average interruption frequency index (SAIFI), the system average interruption duration index (SAIDI) and the customer average interruption duration index (CAIDI) were used. Using the example of an eight-node radial distribution system, reliability was estimated for each distribution section, as well, as at each load point. For the examined distribution sections and load points, three basic reliability parameters were also obtained, i.e., the average failure rate, average outage time and average annual outage time. For a radial distribution system, important customer-oriented indices were estimated, i.e., system average interruption frequency index, system average interruption duration index and customer average interruption duration index. The resultant data allow characterizing reliability and other associated indices, which is relevant for power distribution systems.