When entering the realm of Medium Voltage (MV) power distribution—typically ranging from 6kV to 33kV—cable design becomes significantly more complex than low-voltage systems. The most critical component that overseas buyers and utility engineers debate is the metallic screen layer.

In an MV cable, the metallic screen is not just an arbitrary ground; it controls the electrical field, carries fault currents, and protects personnel.

But when should you specify Copper Tape Screen (CTS), and when is a Copper Wire Screen (CWS) mandatory? Choosing incorrectly can lead to unsafe grounding or excessive material costs.

Understanding the Two Primary Shielding Methods

Option A: Copper Tape Screen (CTS)

This design utilizes one or two layers of thin copper tape applied helically over the semi-conductive insulation screen.

Pros: It provides 100% electromagnetic coverage, keeping the electrical field perfectly uniform. It is highly effective at minimizing electromagnetic interference (EMI) and is typically more compact, resulting in a slightly smaller overall cable diameter and lower weight.

Cons: Because the copper tape is very thin (usually 0.1mm to 0.2mm), its cross-sectional area is small. Consequently, it cannot carry high short-circuit fault currents for prolonged periods without melting.

Option B: Copper Wire Screen (CWS)

This design consists of a concentric layer of helically wound copper wires, held together by an open-helix copper binding tape.

Pros: The primary advantage is fault current capacity. Engineers can customize the total cross-sectional area of the copper wires (e.g., 16mm², 25mm², 35mm², or 50mm²) to match the calculated short-circuit fault levels of the substation or local grid.

Cons: It adds significant material cost, increases the cable's bending radius, and makes stripping and termination more labor-intensive for installation crews.

The Selection Framework: How to Specify

To keep your project safe without overpaying, use this quick checklist when sending out your Request for Quote (RFQ):

1.Check the System Grounding: If the MV network is solidly grounded (high earth-fault current potential), you almost always need a Copper Wire Screen sized to handle that specific fault current. If the system is grounded through a resistor or arc-suppression coil (limiting fault current), a Copper Tape Screen is often sufficient and highly cost-effective.

2.Evaluate Installation Environment: For industrial plants, commercial buildings, or projects requiring tight bends in cable trenches, Copper Tape Armor/Screening offers better flexibility. For long-distance utility distribution lines pulled through conduits with high mechanical stress, Copper Wire Screening provides better structural pulling strength.

Quality Warning: Look for "Triple Co-Extrusion"

Regardless of the shielding type, ensure your manufacturer utilizes triple co-extrusion (Conductor screen, XLPE insulation, and Insulation screen extruded in a single operation under dry curing). This process prevents micro-voids and moisture ingress, eliminating the risk of "water treeing"—the leading cause of premature MV cable insulation breakdown.

Are you currently calculating the short-circuit current and selecting cables for your next medium-voltage power grid project? Contact our chief engineer for a free customized technical solution and quotation.