Medium Voltage Unarmoured Cable: Selection, Applications, and Installation Requirements

Medium voltage unarmoured cable is a screened power cable without a separate metallic armour layer. It is commonly considered for installations where the cable is protected from impact and crushing by its route, such as in buildings, cable trenches, or ducts. Choosing the right design means matching its voltage rating, conductor, insulation, screen, sheath, and installation conditions to the project specification. This guide explains how to evaluate those factors and what to confirm before ordering or installing cable.

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Who This Guide Is For

This guide is intended for electrical contractors, project engineers, distributors, and procurement teams assessing medium voltage cable for a new installation or replacement project. It can help establish the information needed for a technical enquiry, but it does not replace the project design, applicable electrical codes, or advice from a qualified engineer. Requirements can differ by country, utility, installation method, and cable standard. Confirm the governing specification before selecting a product.

What Is Medium Voltage Unarmoured Cable?

“Unarmoured” means the cable has no separate armour layer intended to provide mechanical protection. It does not mean that the cable has no screen: medium voltage designs typically include insulation screening and a metallic screen, with construction selected to meet electrical and earthing requirements. The outer sheath protects the cable from environmental exposure specified for its use, but it should not be treated as a substitute for armour where impact or crushing protection is required.

Medium voltage is classified differently across standards and markets. Cable designations such as 6/10 kV, 8.7/15 kV, and 12/20 kV are examples of ratings used for different system conditions; they are not interchangeable labels. The correct rating depends on the system voltage, earthing arrangement, fault conditions, and applicable standard. A project engineer should confirm the required U₀/U (and Um, where specified) rather than selecting by the system voltage alone.

Typical Construction and Material Options

Conductor and insulation

Conductors are commonly specified in copper or aluminium. Copper offers higher electrical conductivity for a given conductor size, while aluminium may be considered where conductor weight or material cost is a project factor. The choice also affects termination design, jointing procedures, and the cable’s dimensions, so evaluate the complete installation rather than comparing conductor prices alone.

Cross-linked polyethylene (XLPE) is widely used as medium voltage insulation, although the required insulation material must follow the project specification and market requirements. A typical screened design includes a conductor screen, insulation, insulation screen, metallic screen, and outer sheath. The metallic screen provides a defined electrical path as designed; it is not the same as mechanical armour. Ask the supplier for a construction drawing and confirm the screen material, cross-section, and earthing arrangement.

Sheath and cable configuration

Sheath material and cable configuration should reflect the route and environment. Consider moisture exposure, sunlight, chemicals, temperature range, fire-performance requirements, and whether the cable will be installed indoors, outdoors, in a duct, or in a trench. For single-core cables, also verify the planned arrangement and screen bonding method, as these can affect induced currents and losses. Do not assume that a standard sheath or configuration meets every site requirement.

Applications and Suitability

Unarmoured medium voltage cable can be suitable where the route provides adequate mechanical protection and the design complies with local requirements. Possible applications include protected building services, cable ducts, enclosed electrical rooms, and selected industrial or utility routes. Suitability depends on the full installation design, not simply whether the cable is described as indoor or underground.

It may be a poor fit for routes exposed to vehicle traffic, excavation, severe impact, or other mechanical hazards unless additional protection is specified. Depending on the project, that protection may come from a duct, barrier, enclosure, or an armoured cable design. A route survey and risk assessment help determine whether the cable construction is appropriate. If conditions are uncertain, resolve them before finalizing the cable schedule.

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A Practical Selection Framework

1. Confirm the electrical system

Record the nominal system voltage, highest system voltage where applicable, phase arrangement, earthing method, and expected fault conditions. Use these details to confirm the cable voltage designation with the designer and supplier. Also establish whether the project specifies IEC, a national standard, a utility specification, or another technical basis. Standards and local rules can set requirements for construction, testing, and installation.

2. Define the load and conductor requirements

Conductor sizing should be based on the expected load and the actual installation conditions. The calculation may need to consider current-carrying capacity, ambient and soil conditions, grouping, installation method, voltage drop, and short-circuit withstand. Provide the supplier with the required conductor material and cross-sectional area, or request technical review against a complete set of project inputs. Do not select a size from load current alone.

3. Specify construction and environment

State the conductor, insulation, screen, sheath, number of cores, and any required fire, moisture, or chemical performance. Identify whether the cable is exposed to sunlight, installed in a water-prone area, or routed near other services. For unarmoured cable, describe the mechanical protection provided along the route. This information helps suppliers assess whether the requested construction matches the intended service.

4. Review installation and accessories

Plan the cable route, pulling method, drum position, joints, terminations, and screen bonding before installation. Minimum bending radius and maximum pulling tension vary by cable design and manufacturer instructions, so obtain the values for the exact product rather than applying a generic rule. Confirm compatible joints and terminations for the conductor, insulation diameter, voltage class, and screen arrangement. Installation and testing should be carried out by qualified personnel using the project procedures.

Installation Requirements and Common Mistakes

Before pulling, inspect the cable drum and sheath for visible damage, check that the cable identification matches the approved schedule, and verify the route is clear. Use suitable rollers and pulling equipment to avoid excessive tension, sharp bends, or abrasion. Keep the cable sealed during storage and installation when required by the manufacturer, especially where moisture ingress could affect the cable end. Record drum identification and installation details for traceability.

Common errors include treating the metallic screen as armour, overlooking mechanical hazards, selecting voltage rating from nominal voltage alone, and assuming all XLPE cables share the same installation limits. Another frequent issue is ordering cable without confirming termination compatibility or screen bonding requirements. Resolve these points during technical submittal review, not after delivery. If the route or environmental conditions change, reassess the cable specification before installation.

Pricing, MOQ, and Lead-Time Considerations

Pricing depends on the voltage rating, conductor material and size, number of cores, insulation and sheath construction, screen details, order length, and applicable testing or documentation requirements. Minimum order quantities and production lead times are supplier- and specification-dependent, so they should be confirmed for the requested design rather than assumed. Custom constructions or project-specific approvals may require additional review. For a useful quotation, provide the cable schedule, applicable standard, total quantity, delivery destination, and requested delivery date.

Supplier Evaluation Checklist

Before placing an order, check that the supplier can clearly confirm the proposed cable construction and its alignment with your specification. Request a technical datasheet, dimensional information, applicable routine test documentation, packing details, and any project-required inspection documents. Confirm how deviations will be identified and approved, and ask who will handle technical questions during production and installation planning. Zhongdong Cable can review the requested specification and discuss suitable cable options, documentation, and quotation requirements based on the project information provided.

• Confirm voltage designation, standard, and system details.
• Verify conductor, insulation, screen, sheath, and cable configuration.
• Check route protection, environmental conditions, and installation limits.
• Agree on documentation, quantity, delivery terms, and approval process.

Key Takeaways

• Unarmoured cable has no separate metallic armour, so the route must provide suitable mechanical protection where required.
• Voltage rating, conductor sizing, screen design, sheath, and installation method must be assessed together.
• Use manufacturer-specific bending and pulling limits and verify accessory compatibility before installation.
• Supplier quotations are more accurate when the project standard, cable schedule, quantity, and delivery requirements are complete.

Conclusion: How to Move Forward

Medium voltage unarmoured cable is a suitable option when its electrical design meets the system requirements and the installation route provides the necessary mechanical protection. Start by confirming the applicable standard, voltage designation, load and fault conditions, route environment, and accessory requirements. Then compare supplier proposals against the same approved specification, including documentation and delivery terms. To evaluate options with Zhongdong Cable, share your cable schedule and project conditions so the requested construction can be reviewed before quotation and procurement.