Voltage drop analysis and leakage suppression design for mineral-insulated cables

The influence of materials of mineral-insulated (MI) cables on their electrical characteristics upon exposure to high-temperature conditions was examined via a transmission test, in the objective of achieving the stability of the potential distribution along the cable length. Occurrence of a voltage drop along the cable was confirmed for aluminum oxide (Al 2 O 3 ) and magnesium oxide (MgO), as insulating materials of the MI cable. A finite-element method (FEM)-based analysis was performed to evaluate the leakage in the potentials, which was found at the terminal end. Voltage drop yields by the transmission test and the analysis were in good agreement for the MI cable of Al 2 O 3 and MgO materials, which suggests the reproducibility of the magnitude relationship of the experimental results via the FEM analysis. To suppress the voltage drop, the same FEM analysis was conducted, the diameter of the core wires (d) and the distance between them (l) were varied. Considering the variation of d, the potential distribution in the MI cable produced a minimum voltage drop corresponding to a ratio d/D of 0.35, obtained by dividing d with that of the insulating material (D). In case of varying l, a minimum voltage drop was l/D of 0.5.