New approach in distribution system reliability analysis considering protection system miscoordination

The reliability analysis of the distribution system usually implies that the protective devices and their corresponding elements for measuring the necessary signals are ideally reliable and that they operate selectively and without time delay. However, practice shows that the coordination of protective devices is not always done correctly. In addition, due to aging or incorrect selection of current transformers (CTs), CTs can often enter saturation during faults or overloads in the network, which can further compromise the selective operation of the protection systems and affect the reliability of the system. In this paper the assessment of the reliability indicators of the distribution system was carried out. The assessment includes a detailed model of the protection system with an integrated model of CTs, that takes into account the non-linear characteristic of magnetization. Therefore, the potential saturation of CTs was taken into account in the analysis. The paper presents and compares the results obtained analytically and by applying the Monte Carlo simulation, which include the uncertainties of short-circuit fault input data.