Magnetic shielding of buried high-voltage (HV) cables by conductive metal plates
Purpose - To study the magnetic shielding of buried high-voltage (HV) cables by adding conductive metal plates on the ground surface above the cables. Design/methodology/approach - The field is calculated with eight rectangular conductive plates above the cables, positioned with their long edge either parallel to the cables or transversal to the cables. Here, the circuit method is used. In this method, the shield is replaced by a grid of straight filaments in which the unknown currents are searched by solving an electrical circuit. Findings - It is observed from the calculation results that it is important to have a perfect electrical connection between adjacent plates. In the area above the shield, an "infinite" contact resistance between neighbouring plates results roughly in double field amplitude compared to the situation with contact resistance zero. The positioning of the rectangular plates (parallel or transversal to the cables) has not much influence on the shielding. The shielding efficiency as a function of the shield size is studied as well. The circuit method is validated by measurements on an experimental setup at reduced scale. Research limitations/implications - The circuit method is applied to conductive objects and not to ferromagnetic objects. Practical implications - As the circuit method is rather fast also for 3D geometries with thin plates, the shielding of HV cables can be evaluated in a computationally more efficient way than by using, e.g. finite elements. Originality/value - The circuit method is already described in the literature. The originality of this paper is the study - by this circuit method - of the effect of several parameters (size of the shield, contact resistance, orientation of the plates) on the shielding efficiency.
magnetism high voltage circuit theory magnetic fields