Programa de Pós-graduação em Engenharia Elétrica e da Computação

URI Permanente desta comunidade

http://200.137.215.59/tede/handle/tde/262

Navegar

Navegando Programa de Pós-graduação em Engenharia Elétrica e da Computação por Por Orientador "Almeida, Maria Leonor Silva de"

Agora exibindo 1 - 3 de 3
  • Nenhuma Miniatura disponível
    Item
    Modelagem e proteção de reatores shunt do tipo seco com núcleo a ar
    (Universidade Federal de Goiás, 2020-02-27) Ribeiro, Jan Augusto Rocha; Almeida, Maria Leonor Silva de; http://lattes.cnpq.br/7955955842189669; Almeida, Maria Leonor Silva de; Silva, Kleber Melo e; Kopcak, Igor
    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.
  • Nenhuma Miniatura disponível
    Item
    Proteção diferencial baseada nas correntes de sequência zero e de neutro para reatores shunt com núcleo de ar tipo seco
    (Universidade Federal de Goiás, 2021-06-30) Santos, Guilherme Gomes dos; Almeida, Maria Leonor Silva de; http://lattes.cnpq.br/7955955842189669; Almeida, Maria Leonor Silva de; Garcés Negrete, Lina Paola; Silva, Kleber Melo e
    The growing increase in the number of long transmission lines, with high voltage levels, makes necessary the connection of parallel shunt reactors in the lines, as a way to circumvent the consequences of overvoltage, due to the capacitive effect of the lines. The use of shunt reactors enables voltage regulation, by absorbing the excess of capacitive reactive in the line. Considering the important role of shunt reactors for the correct operation of long transmission lines, it is essential to guarantee protection logics that allow the quick identification of short circuits inside this equipment. Therefore, this work presents a differential protection algorithm based on the analysis of zero and neutral sequence currents, which identifies abnormal operating conditions in the shunt reactor and, consequently, allows a safe and selective operation of the protection for turn-to-ground and turn-to-turn faults. This logic is based on the comparison of the zero sequence current, calculated on the basis of the phase currents, measured near the bushing, with the current measured in the neutral winding. The zero sequence and neutral current phases of the reactor are reconstructed in time and, finally, are compared, allowing the identification of the short circuit within the reactor. In addition, the algorithm incorporates a function that detects the occurrence of disturbances of an internal or external nature to the reactor. Simulations were performed using the software Alternative Transient Program (ATP), in which a 230 kV, 380 km transmission line with 50 % of compensation was modeled, such that, in the reactor, different internal short circuits were applied, of the turn-to-ground and turn-to-turn faults. Furthermore, in order to perform a comparative evaluation, the proposed algorithm was analyzed together with the traditional differential protection Restricted Earth Fault-(REF), which uses the same input signals. From the results obtained, it was found that the traditional protection did not operate for turn-to-ground with high fault resistance, and was also not able to identify any of the analyzed turn-to-turn faults. On the contrary, it was verified that the proposed algorithm operates correctly for all the turn-to-ground and turn-to-turn faults tested, independently of the variations in the value of the dispersion factor, the number of turns involved and the value of the fault resistance. Futhermore, it is worth to mention the fast speed operation of the proposed protection Also noteworthy was the speed in which the proposed algorithm, which identified all the faults analyzed with an approximate operation time order of 1 ms after their occurrence. It should be noted that in order to guarantee the correct performance of the proposed protection for all external short circuits, it is necessary to use additional logic to guarantee non-reaction for external faults.
  • Nenhuma Miniatura disponível
    Item
    Avaliação da proteção de distância em linhas de transmissão de circuito duplo com estudo de caso
    (Universidade Federal de Goiás, 2020-10-30) Silva, Jéssica Cristina Marques da; Almeida, Maria Leonor Silva de; http://lattes.cnpq.br/7955955842189669; Lopes, Felipe Vigolvino; Kopcak, Igor; Almeida, Maria Leonor Silva de
    Approximately 20% of the transmission lines of the Brazilian national interconnected system are double circuit, being the most used configuration type after single circuit transmission lines. For this reason, the importance of studying double circuit transmission lines is highlighted. When two transmission lines are close, such as a double circuit transmission line, a mutual zero sequence coupling is observed between them. This mutual zero sequence coupling interferes in the impedance calculated by the distance protection, in the case of short circuits involving the ground, due to the zero sequence current in the healthy parallel line and the presence of zero sequence mutual impedance. Considering the distance protection applied to double circuit transmission lines, this dissertation presents a comparative assessment between traditional and compensated distance protections, which considers the influence of the operating condition of the parallel circuit on the protected line. In addition, the distance protections are assessed using phase comparators, such that in the results the impedance units operation is analyzed. For this purpose, a 138 kV real transmission system is modeled in the Alternative Transient Program (ATP) software and subjected to single phase-to-ground fault, varying the fault resistance value, the system loading, the power of the sources, the fault line and the fault location in each line. From the results obtained, it is verified that the correction of the mutual zero sequence coupling can improve or worsen the performance of the distance protection in relation to the function 21 traditional, which depends on power of the sources and the fault location. Thus, it is emphasized that for the cases analysed the correction of the mutual zero sequence coupling does not significantly improved the performance of the distance protection.