Influência da condutividade e permissividade do solo em função da frequência no cálculo da impedância longitudinal e admitância transversal de linhas aéreas de transmissão / Influence of earth´s conductivity and permittivity frequency dependence on longitudinal impedance and transversal admittance transmission line´s parameters calculation

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

22/04/2010

RESUMO

This thesis aims to propose more accurate models for calculating the electrical parameters of overhead power transmission lines. The influence of earth s conductivity and permittivity frequency dependence is evaluated when calculating transversal and longitudinal transmission lines parameters in the frequency range 0 to 2 MHz. This frequency range covers the majority of the electromagnetic transients in electrical systems (switching transients, faults transients, load rejections, harmonic disturbances, etc). Between 1 kHz to 2 MHz, the product of the signal angular frequency (w) by the dielectric constant (eg) of the soil may have the same order of magnitude as the conductivity (sg), due to the variation of these parameters with frequency. Therefore, the assumptions of low frequency traditionally used - the soil conductivity (sg) considered as constant and weg that can be negligible (sg >>weg) - can lead to incorrect models that do not adequately represent the transmission line s response, in cases of fast transients phenomena (with frequency spectrum above 1 kHz). The importance of properly considering the frequency dependent soil model is presented for the one-conductor case and for a single three-phase transmission line (440 kV, considered ideally transposed). The aim is to compare the transmission line parameters calculated considering the conductivity and weg frequency dependence ground model in relation to the common ground representation, with constant conductivity and weg that may be neglected. It is also compared the results obtained from the complex plane method with those obtained from the Carson s modified expressions for longitudinal parameters and between Carson s modified potential-coefficient correction factors and from the most common approximated methods for transversal admittance parameters

ASSUNTO(S)

condutividade elétrica transitórios (eletricidade) campos eletromagnéticos linhas elétricas aéreas dispositivos eletromagnéticos electrical conductivity transients (electricity) overhead electrical lines electromagnetic fields electromagnetic devices

ACESSO AO ARTIGO

Documentos Relacionados