Modelling and simulation of the ice melting process on a current-carrying conductor.

摘要

The general objective of this PhD study is to develop mathematical models that determine the current and energy requirements of thermal de-icing and ice prevention methods based on the Joule effect under various meteorological and current transmission conditions. The analytical model predictions were compared to experimental results for the purpose of assessing the predictive power of the models.; First, an ice prevention model was established to calculate the minimum current intensity required to inhibit ice formation on a single power line conductor. Correction factors, taking into account water runback on the conductor surface as well as deviation of the water layer from the thermal equilibrium state, are introduced for three specific ACSR conductors. The model results accord well with the measurements taken in an icing research wind tunnel. In order to complete the model, it was necessary to assess the overall heat transfer coefficient (HTC) for stranded conductors. The overall HTC for bare overhead conductors with different surface geometries was obtained from measurements and from numerical simulations.; Secondly, a computational model using finite differences was developed which calculates the current and energy requirements for de-icing partially ice covered conductors. Two heating techniques were analyzed, namely Joule heating by ac current and by impulse current, for a large number of atmospheric parameters. Both techniques can be used with different strategies depending on the time of interaction in the ice accretion process. In order to complete the model, the assessment of radial equivalent thermal conductivity of the ACSR conductor is required. This thermal conductivity was estimated from both experiments and various theoretical models.; Thirdly, experimentally validated analytical approaches have been proposed to determine the shedding time and corresponding energy required to de-ice a completely ice covered conductor by heating with increased nominal ac current. This procedure is able to give a fast estimation of the required Joule heat to totally remove the ice around the conductor as a function of the different influencing factors.; This thesis presents experimentally validated mathematical models, which can efficiently be used to calculate the current and energy requirements of de-icing conductors or of preventing ice accretion on a single power line conductor.