Abstract
This paper aims at studying the effect of cable characteristics on the thermal instability of 320 kV and 500 kV Cross-Linked Polyethylene XLPE-insulated high voltage direct-current (HVDC) cables buried in soil for different values of the applied voltages, by the means of sensitivity analysis of the insulation losses to the electrical conductivity coefficients of temperature and electric field, a and b. It also finds the value of dielectric loss coefficient βd for DC cables, which allows an analytical calculation of the temperature rise as a function of insulation losses and thermal resistances. A Matlab code is used to iteratively solve Maxwell’s equations and find the electric field distribution, the insulation losses and the temperature rise inside the insulation due to insulation losses of the cable subjected to load cycles according to CIGRÉ Technical Brochure 496. Thermal stability diagrams are found to study the thermal instability and its relationship with the cable ampacity. The results show high dependency of the thermal stability on the electrical conductivity of cable insulating material, as expressed via the conductivity coefficients of temperature and electric field. The effect of insulation thickness on both the insulation losses and the thermal stability is also investigated.
Highlights
Thermal Instability in high voltage direct-current (HVDC) ExtrudedHigh voltage direct-current (HVDC) cables have progressively been used in high voltage (HV) transmission systems to meet the increasing energy demand [1]
The increase in both the applied voltage and the electric field justifies the need to investigate the insulation losses, which may lead to temperature rise and in some cases to thermal instability [3]
This paper studies the intrinsic thermal instability—due to the electric field rise or to the effect of cable insulation characteristics—in XLPE-insulated HVDC cables buried in soil
Summary
High voltage direct-current (HVDC) cables have progressively been used in high voltage (HV) transmission systems to meet the increasing energy demand [1]. Cable manufacturers are working on innovative materials to withstand higher voltages to meet the increasing demand. HVDC cables have been qualified at rated voltages up to 640 kV [2]. The increase in both the applied voltage and the electric field justifies the need to investigate the insulation losses (i.e., dielectric losses or leakage current losses), which may lead to temperature rise and in some cases to thermal instability (thermal runaway) [3]. In DC cables, insulation losses are fully driven by leakage current [1]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call