Modeling of dielectric properties of low voltage cables

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Supervisor:
Dr. Tamus Zoltán Ádám
Department of Electric Power Engineering

Electric insulators are subject to thermal, electric, mechanic etc. stresses, because of which their molecule structure changes and they age. The typical degradation phenomena are determined by both the industrial environment and the molecular structure. Structure of the polymer insulators is largely affected by the additives like stabilizers and even colorants. Consequently a cable’s different colored insulators can degrade in different ways, thus making it necessary to measure their condition with good precision. Low voltage cables usually don’t have shielding on their cores’ insulation, so in case of their dielectric measurement the data collected is affected the other cores’ insulators and the jacket, and whether the cable has shielding or not.

I created the COMSOL Multiphysics model of a specific cable with four cores and shielding and simulated insulation resistance measurements. I performed the same measurements on the actual cable, and by comparing the data I concluded that the measurements confirm the results of the simulation.

The aim of the simulation was to determine how the different cable test connections and the difference of a single core’s insulation resistance affect the measurement’s results. I created the diagrams showing the sensitivity of the measured resistance to the core’s resistance using each of the possible test connections. Then I created the model of the same cable, but without the shielding and performed the same examinations. Finally I concluded the results and made recommendations on which connections to use in case of measuring shielded and unshielded cables’ cores.

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