Copper Wire and Tape Screening

Copper Wire and Tape Screening

Copper Wire and Tape Screening (CWTS) is a type of metallic shielding configuration used in medium-voltage (MV) and high-voltage (HV) electrical power cables.

It combines two distinct elements—individual copper wires and a helically wrapped copper tape—to provide superior electrical and mechanical performance compared to using either component alone.

1. Components of CWTS

A CWTS layer is typically applied over the semi-conducting insulation screen of a cable and consists of:

• Copper Wires: A layer of helically wound, bare copper wires evenly spaced around the core. These provide the primary path for fault currents.

• Copper Tape (Open Helix/Counter-Helix): A thin copper tape wrapped over the wires. It is often applied in the opposite direction (counter-helix) or with a gap (open helix) to bind the wires tightly, ensuring physical stability and consistent electrical contact.

2. Key Functions

The CWTS serves several critical purposes in a power cable assembly:

• Electrostatic Shielding: It ensures a uniform, radial electric field within the cable insulation, minimizing localized electrical stress that could lead to partial discharge and insulation failure.

• Fault Current Carrying Capacity: In the event of a short circuit or earth fault, the heavy copper wires safely carry the high fault current to the ground, protecting surrounding equipment and personnel.

• Earth Return Path: It acts as a continuous neutral or grounding conductor for charging currents during normal operation.

• Mechanical Protection: The combination of wires and tape offers robust physical protection to the underlying cable core during installation and service.

3. Advantages of CWTS

Feature	Advantage
High Fault Capacity	The cross-sectional area of the copper wires can be easily adjusted during manufacturing to meet specific short-circuit current requirements.
Excellent Contact	The copper tape ensures that all individual wires remain in constant electrical contact, preventing voltage differentials between wires.
Flexibility	Despite its robust protection, the wire-and-tape configuration allows the cable to remain relatively flexible during routing and installation.
High-Frequency Performance	The tape layer helps close the gaps between wires, improving electromagnetic interference (EMI) shielding.

4. Common Applications

CWTS cables are widely specified in demanding utility and industrial environments, including:

• Electrical substations and power distribution networks.

• Renewable energy projects (wind and solar farm collection systems).

• Industrial plants requiring high reliability and specific short-circuit ratings.