Coordenação de isolamento para transitórios de manobra considerando a forma de onda da sobretensões

AUTOR(ES)

Rafael Renno Nunes

DATA DE PUBLICAÇÃO

2006

RESUMO

This work develops a new insulation coordination procedure for transmission lines, considering the influence of the individual characteristics of switching overvoltage waves on the insulation strength. The purpose is to assess how the waveshapes of the transient overvoltages affect the risk of flashover and the air gaps needed, instead of adopting a fixed strength, associated to the critical wave condition, as is normally done. By studying the insulation discharge aspects, a new methodology is created, which determines the probability of flashover including the favourable effect of the usually long wave front and the negative impact of the bumps. The comparison of the results obtained by different alternatives permits choosing a technique for processing the overvoltage signals, able to extract the wave parameters of influence and establish with good precision the variable behaviour of the insulation when subjected to different types of stress. As the reclosing and energization overvoltages depend on the closing times of the circuit breaker poles, the transients are processed for a series of statistical operations. A comparative analysis between the overvoltages obtained for a 1050 kV transmission line and published results proves the appropriate modelling of the system; changes on the configuration were then made so as to evaluate a wider group of situations. The proposed insulation coordination procedure allows a more refined calculation of the risk of flashover of the simulated systems. Its application on the insulation coordination of transmission lines supplied by a complex source defines air gap lengths very close to the ones obtained by the traditional procedure, because of the high frequency content of the generated transients in this kind of system. For systems with inductive source, there is a significant reduction of the insulation distances for predetermined risks of flashover, in comparison with the gap spacing defined by the traditional approach, which could lower the costs of new projects. The importance of a good description of the region of low flashover probability was also appraised, through the estimation of the standard deviation of normal distributions or the use of other distributions.

ASSUNTO(S)

engenharia elétrica teses.

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