Modelagem e proteção de reatores shunt do tipo seco com núcleo a ar
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2020-02-27
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Universidade Federal de Goiás
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The use of long and high voltage level transmission lines is common in countries with large territorial extensions, since they allow the transmission of electric energy between regions physically distant from each other. Despite of this advantage, long lines with high voltage level operate with high capacitive effect, which results in the increase of the voltage in some points of the system. These overvoltages are harmful because they result in heating, compromising the integrity of electrical equipment. In order to overcome overvoltage problems due to line capacitive effect, there can be used reactors in parallel to the line. These reactors absorb the excess of capacitive reactives in the line, improving voltage regulation. Therefore, due to its importance for line and electrical system operation, it is essential to ensure the shunt reactor’s correct operation. Normally in systems with voltages equal to or greater than 230 kV, iron core reactors immersed in oil are used. However, due to technological advances, air-core reactors have been developed to be installed at systems with voltages up to 345 kV. Since it does not have oil or iron core, this type of reactor causes less losses, is easier to install and requires less maintenance. Considering the benefits of aircore shunt reactors and their relevance to the system’s correct operation, this work proposes to develop both a model and a protection applicable to this equipment. The proposed model allows the analysis of the reactor’s behavior under nominal operating conditions and also in different situations of internal faults (turn-to-ground and turnto-turn faults). For the evaluation of the proposed model, reactor currents are verified against the influences of fault type, number of turns involved in faults, dispersion factor, position of the fault in the coil and value of fault resistance. Furthermore, it is proposed a differential protection which compares zero sequence currente on phase winding to current in ground winding. This current signals comparation is based on an adapted alpha plane. In order to validate the developed proposals, simulations were carried out using Alternative Transient Program software (ATP), wherein is simulated a 230 kV transmission line, 380 km with 50% shunt compensation. In this scenario, different faults were applied to the reactor in order to evaluate the proposed model and it’s protection. In addition, the proposed protection is compared with a protection traditionally employed for a correspondent reactor, restricted earth fault (REF), which confirms the best performance of the proposed protection. Finally, is concluded that the proposed model is a good alternative to represent the air-core dry reactors. In addition, it is concluded that the proposed protection guarantees the integrity of this equipment against different types of faults.
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RIBEIRO, J. A. R. Modelagem e proteção de reatores shunt do tipo seco com núcleo a ar. 2020. 113 f. Dissertação (Mestrado em Engenharia Elétrica e da Computação) - Universidade Federal de Goiás, Goiânia, 2020.