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This work proposes two new approaches based on the ordinary least-squares method and the total least-squares method to estimate the parameters of a balanced three-phase transmission line using voltage and current measurements from phasor measurement unit. First, a new model for the steady-state phasorial equations of a medium-length transmission line is proposed. Then, the noises acting upon each measurement on the ordinary least-squares setup are considered, and for the total least-squares setup, noise acting upon the observation matrix in order to account for model uncertainties and non-linearities is also considered. The methods are tested in simulation data of a real medium-size transmission line.s The main goal is to compare both methods and show their complexities. The results show good performances for both methods and, indeed, the total least-squares setup had better performance than other reported total least-squares estimators, which use a different phasorial set of equations and oversimplified noise modelling. It is concluded that for the ordinary least-squares, the solution is well known and its behavior is predictable. While for the total least-squares, the solution requires more sophisticated methods of matrix decomposition and its behavior is not as predictable. Therefore the implications of these new approaches, where new considerations about the modelling of the noises are made and where a new phasorial set of equations is used are significant, given that the many works in the literature make use of these commonplace tools.

CAPES, pelo apoio financeiro que me permitiu a conclusão desta pesquisa. Ao orientador, Prof. Dr. Eduardo Coelho Marques da Costa, pela disposição em ajudar tanto profissionalmente como pessoalmente. À coorientadora, Prof. a Dr. a Luisa Helena Bartocci Liboni, pelo acompanhamento pontual e competente. Ao Prof. Dr. José Humberto Araújo Monteiro, da Universidade Federal do Acre, por tornar possível a realização deste mestrado. Aos demais professores que conheci ao longo desta jornada. À minha companheira, Cíntia Peixoto, por todo apoio e incentivo prestados. A todos os que direta ou indiretamente contribuíram para a realização desta pesquisa. A todos os membros da banca. Resumo Pereira, R. F. R. Estimação de parâmetros de linhas de transmissão por meio de técnicas de identificação de sistemas. 170 p.

The parameter estimation for transmission systems is important to power flow analysis, planning the expansion of electric power systems, stability, dispatch and economic analysis. This type of task is developed through systems identification methods, being the least squares method and its variations the most common techniques to obtain the transmission line parameters. However, these techniques have some disadvantages, such as non-recursive parameter estimation or the availability of an ideally transposed line, in order to address a problem with symmetric matrices, which simplifies the estimation process. In this paper, a non-linear method (Extended Kalman Filter) is presented to obtain the states of the transmission line terminals jointly with the vectorized matrix of parameters; such approach is strongly affected by the initial conditions; these conditions are usually obtained manually, which requires a lot of time and effort. Therefore, an optimization method (Particle Swarm Optimization) is applied in order to improve the convergence of the EKF, which reduces the time for adjusting the hyper-parameters and improves the estimated results. The proposed method showed accurate results for non-transposed systems, and also in comparison with results obtained from the same EKF-based method without the proposed optimization technique.