The Role and Difference of Metal Shielding for Medium Voltage Cables

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Metal shield, as an important structure of medium voltage power cable, will pass capacitive current under normal operation of the cable and act as a pathway for short circuit current in the event of a short circuit.

It also shields the electromagnetic field generated when the cable is energized in the insulating core to reduce electromagnetic interference to the outside world.

Copper tape can also be used for gap packaging. Single-core cable shielding with copper tape nominal thickness of not less than 0.12mm.

The copper wire shield is composed of loosely wound soft copper wire, the surface of which is tightly bound with counter-wound copper wire or copper tape. The average gap between adjacent copper lines is not more than 4mm.

The shielding method of copper wire and copper tape winding can structurally improve the disadvantages of the copper tape winding shielding method. There is neither an oxidation layer generated by overlapping copper tape nor strong bending and hot and cold deformation, and the copper tape winding is not easily arching embedded in the insulating shield.

The cross-section of the metal shield directly affects the ability cable can withstand short-circuit current in the event of a fault. If the cross-section is too small, the short-circuit current will overheat or burn the insulation.

Therefore, it is necessary to determine the cross-section of the metal shield according to the fault current capacity. In cables up to 10 kV, when the conductor cross-section exceeds 500, try to use a copper wire shield!

If you insist on copper tape shielding, you need to thicken the thickness of the copper tape! Depending on the cable laying, it is recommended to use copper wire shielding if it is necessary to carry larger short-circuit currents.

Therefore, the difference between copper tape shielding and copper wire shielding is the ability to carry short-circuit current. Copper wire is slightly larger (also depends on the effect of copper wire). Copper tape has a uniform magnetic field and shielding effect.

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