Análise da tensão de restabelecimento transitória em disjuntor de alta tensão: estudo de caso em uma instalação elétrica industrial

Abstract

The electrical system is subject to several types of failure occurrences, short circuits and abnormal operating conditions, thus producing transients in the network. For these reasons, it is essential that circuit breakers play their role in ensuring the protection and integrity of electrical installations. Thus, they require special attention in their dimensioning and studies of overcoming by Transient Recovery Voltages (TRVs). The most common types of faults in electrical installations are short circuits, so the equivalent impedances in the electrical system undergo changes. As a result, operational risks of circuit breakers already installed and overrun by TRV increase. In view of all this, there are IEEE STD C37.011-2011 and IEEE STD C37.04b- 2008 standards that are technical guides for the analysis and specification of circuit breakers, establishing maximum capacities to avoid overruns against TRV. These patterns helped in the understanding and evaluation of the circuit breaker object of this case study. Thus, this study aims to evaluate the performance with a focus on TRV of an SF6 gas insulated circuit breaker from a 69 kV substation located in an industrial electrical installation. Different study scenarios are investigated such as, for example, complete circuit representing the electrical installations of the substation and simplified electrical circuit of this substation. In addition, for this TRV analysis, the actual intrinsic capacitance values of the equipment and values recommended by the IEEE STD C37.011standard were used. Furthermore, changes were caused in the equivalent impedances of the electrical network and in the voltage level, presupposing a change in characteristics of the electrical system of the distributor agent. The simulations were performed using EMTP/ATP and its ATPDraw graphics preprocessor. The results show the need to carry out a detailed TRV analysis during the development of a substation project, to ensure the proper sizing of the circuit breaker for a specific application. Another objective of this work was to analytically model the simplified electrical circuit of the electrical installations of the substation. Therefore, with this mathematical equation a TRV signal was reproduced, and this signal was compared with the results presented by the ATP/EMTP and PSIM software. Thus, the work also contributes to the development of analytical modeling presented for TRV analysis. The result of the TRV signal found through this proposed method was satisfactory and consistent, thus becoming a tool for comparing the result in this case study.