Návrh chránění trafostanic 22 kV zapojených do smyčky

Abstract

This diploma thesis deals with the design of protection of four new 22 kV transformer stations, which are permanently connected in a loop. In this network, I solve the design of protection against basic fault conditions, which are overload, short-circuit and earth fault. This is ensured by the use of the IED REF620 with overcurrent and earth fault protection functions, both directional and non-directional. The diploma thesis is divided into theoretical and practical part of the solution. As for the theoretical part of the diploma thesis, in the first chapter I present an analysis of electrical protections and in the second chapter I present an analysis of the calculation of short-circuit currents. In the practical part of the diploma thesis, I first describe the connection of 22 kV transformer stations and REF620 protection designed to protect these transformer stations. In the fifth chapter I perform calculations of minimum short-circuit currents, maximum through short-circuit currents of transformers and switching currents of transformers. Based on these results, I will further calculate the starting currents of the protections and perform the design and setting of overcurrent protections. For the design and setting of earth protections, I perform calculations of fault capacitive currents and starting currents. At the very end of the diploma thesis, I evaluate the proposed protection system.