A probability based unified model for predicting electrical, mechanical and thermal characteristics of stranded overhead-line conductors

Abstract

<p>This thesis is a report on a Unified Model to predict the performance of Aluminum Conductor Steel Reinforced (ACSR). The Model combines electromagnetic, mechanical, radial conduction, and steady-state thermal models, and uses a probabilistic method to take account of system loads and the stochastic nature of the meteorological parameters. The four models, developed during the past thirty years, have been used by the industry individually to predict the electrical, mechanical and thermal behaviour of stranded overhead conductors. Each aspect was analyzed separately, neglecting dependencies of the involved variables on other aspects of the conductor behaviour. Most results obtained in this way were acceptable while conductors were operating at lower temperatures. However, at high temperatures, the effects that each aspect of the behaviour has on another are no longer negligible. Until now there has not been a feasible mechanism to link the models in order to predict all aspects of the behaviour of the conductor simultaneously, and to take into consideration all the interdependent influences among models. The Unified Model, developed as a result of this work, is a new approach for the simultaneous prediction of all the aspects of conductor behaviour. For the first time all four models: electromagnetic, mechanical, steady-state thermal, and radial conduction models, are coupled such that the conductor is viewed as a whole. In addition, the statistical distribution of system loads, ambient temperature, and rise of conductor temperature above ambient are included in the Unified Model to determine a realistic thermal history of the conductor and to assess annealing in the aluminum layers. This has not been done before. The usefulness of the probability based Unified Model for predicting characteristics of the conductor, such as sag, power loss and loss of tensile strength of nonferrous wires is demonstrated. An example of application of the Model to an ACSR conductor is given. The results are used to study the sensitivity of the electrical, mechanical, and thermal characteristics of the conductor to various parameters and to determine how the electrical, mechanical, and thermal characteristics affect each other. The results are presented in the form of recommendations for the design of the overhead conductors.</p>