Study On Induced Voltage And Protective Grounding Of Cable Metal Sheath

If High voltage single-core cable loads three-phase alternating current,alternating electromagnetic field will be produced in space around the cable. Ascable metal sheath is equivalent to the transformer secondary winding, soinduced voltage will be formed on it due to effect of alternating magnetic field.Higher induced voltage on cable metal sheath not only threats the safety ofbuilder, but also makes metal sheath insulation breakdown. When a loop isformed between the metal sheath and the earth, circulating current loss willgreatly affect current-carrying capacity of cable, Therefore the cable operationtemperature will rise, the service life of the cable will reduce. Even groundingwire could be burned under the influence of heavy heat caused by circulatingcurrent loss and a serious accident and unnecessary economic loss will happen tothe cable lines. So accurate calculation, reducing the induced voltage on cablemetal sheath and make cable metal sheath proper ground become very importantto the safe and stable operation on cable lines.In this dissertation, induced voltage on metal sheath of single-core cablewith random position was first calculated by the analytic formulas based onelectromagnetic induction law and then, simplified3D modeling of metal sheathof single loop cable were accomplished by Ansoft Maxwell15. The results showthat induced voltages on cable metal sheath in horizontal and triangle laying arecorrect and the applicability of the finite element is validated; Then the inducedvoltage on cable metal sheath of multiloop was calculated, and the factors thatdifferent armour coat, metal sheath, half conductive shield material how to affectthe induced voltage value were researched. It was also researched that reducingthe induced voltage through changing the ways to ground with metal sheath, the optimal grounding method under different conditions was determined then.It has important significance for safe, reliable operation of high voltagepower cable by using the finite element method to calculate the induced voltageon cable metal sheath and choosing the best grounding way.