Modelling Thermal Rating of Arbitrary Overhead Line Systems

    Research output: ThesisDoctoral Thesis


    The aim of this project is to identify methods for improving the power transfer capacity of existing overhead power lines (OHL) with changes that require small modifications of the structure. These methods usually involve re-conductoring of the line with larger ‘traditional’, all aluminium alloy conductors (AAAC) or aluminium conductor steel reinforced (ACSR) or more technologically advanced high temperature low sag (HTLS) conductors. These options and their effects are investigated in this thesis by considering the overall OHL system and not only the conductor. Towards this end a holistic computational methodology has been developed to allow sag-ampacity-tension calculations considering electro-mechanical properties of arbitrary OHL systems. This methodology can be used for any aerial power line design to calculate the maximum sag, ampacity and losses developed under specified weather and operating conditions on flat and inclined terrain with common or novel conductors. Surveyed data of three OHL sections were used to verify the accuracy of the methodology. The results showed that the electrical calculations were in all cases very close to the measured values, and also that the sag prediction was correct and more accurate than the existing method of fixed temperature shift on two of the sections.Results are subsequently presented as illustrative applications of this methodology to show potential benefits from such a holistic perspective on the system. Firstly, the mechanical performance of conductors on a 33 kV wood pole OHL system is considered as a continuum and is divided into three main zones of sag which describe the system’s performance for different conductor sizes. Due to the complexity of OHL systems it was considered important to firstly examine the performance of the traditional AAAC and ACSR conductors on the structure and identify the influence of key parameters of the system (OHL strength, conductor strength, conductor weight etc.) on electrical and mechanical performance. This led to the conclusion that AAAC perform better on this particular system than the ACSR conductors due to their lighter design. Another comparison involved HTLS conductors which are known for their high improved performance at elevated operating temperatures (above 90 °C). Results indicated that the aluminium conductor composite core conductors (ACCC/TWs), which have also improved performance at normal operating temperatures, can allow voltage uprating of an existing 33 kV system up to 66 kV. Finally, performance analysis was performed for a 275 kV lattice tower OHL system, and it was found that the composite HTLS conductor types studied can double the ampacity of the lattice tower OHL. It was also found that conductor bundle configuration has better performance due to the reduction in weight and increase in strength. This allows larger conductor sizes on the same OHL structure, a conclusion which also identifies the importance of OHL structure strength on its overall performance.
    Original languageEnglish
    Awarding Institution
    • The University of Manchester
    Publication statusPublished - 2009


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