A probabilistic protection against thermal overloads of transmission lines

An innovative overload protection scheme is proposed to enhance the reliability of classical overload relays. The protection logic includes an accurate thermal model of bare overhead conductors, which allows to explicitly estimate the line temperature using the electrical current and weather conditions. In particular, the climatic variables are suitably represented by stochastic models that include the periodic patterns (seasonality) of meteorological phenomena. In this probabilistic context, the decision whether to trip out the transmission circuit is made according to the stochastic distribution of the conductor temperature, which is evaluated in real-time using an optimal discrete filter. Simulation results show the novel overload protection could increase the reliability of classical relays. (C) 2011 Elsevier B.V. All rights reserved.