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    2. What is power cable?

      來源:思柏科技 日期:2017-1-16 15:18:16

      Medium and high-voltage power cables, in circuits over 2000 volts, will have a shield layer of copper or aluminum tape or conducting polymer. If an unshielded insulated cable is in contact with earth or a grounded object, the electrostatic field around the conductor will be concentrated, resulting in corona discharge, and eventual destruction of the insulation. As well, leakage current and capacitive current through the insulation presents a danger of electrical shock on contact. The grounded shield equalizes electrical stress around the conductor, diverts any leakage current to ground, and blocks capacitive current from flowing into objects (or persons) touching the exterior of the cable.

      Shields on power cables are connected to earth ground. On high current circuits the shields must be connected only at one end, since induced current will flow in the shield. This current will produce losses and heating and will reduce the maximum current rating of the circuit. On very long high-voltage circuits, the shield may be broken into several sections since a long shield run may rise to dangerous voltages during a circuit fault.
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