Low Voltage Cables

A Comprehensive Guide to Low Voltage Cable Types in the UK

Low voltage cables are a broad category of electrical cables designed to operate at voltages not exceeding 1000V AC or 1500V DC, as defined by British Standard BS 7671. The main types are categorised by their application and include general purpose power cables for energy distribution; armoured cables for mechanical protection; specific building wires like Twin and Earth for domestic circuits; specialised industrial control and instrumentation cables for automation; fire performance cables for life safety systems; and data communication cables for networking and media. As leading UK suppliers of electrical cables and accessories, we understand that selecting the correct type is critical for the safety, performance, and compliance of any electrical installation. This guide provides a definitive overview of the key low voltage cable types available.

The world of electrical wiring is governed by precise standards and application-specific requirements. While the term "low voltage cable" provides a broad regulatory classification based on voltage, the true identity and purpose of a cable are defined by its intended use. This dictates its construction, from the conductor and insulation materials to the inclusion of protective armouring or electromagnetic screening. Understanding these distinctions is essential for any professional, as the choice of cable directly impacts everything from the operational efficiency of an industrial process to the safety of a domestic home. In the following sections, we will explore the primary categories of low voltage cables, clarifying their characteristics and the specific environments for which they are designed.

What Exactly Is A Low Voltage Cable?

A low voltage cable is any electrical cable intended for use within a specific voltage range that encompasses the vast majority of domestic, commercial, and industrial power applications. This classification is not about a single product but a wide family of cables governed by a common set of safety and performance standards.

How Is Low Voltage Defined In The UK?

In the UK, British Standard BS 7671 defines low voltage as a voltage exceeding 50V AC or 120V ripple-free DC, but not exceeding 1000V AC or 1500V DC between conductors.

This definition is crucial as it covers standard UK mains voltages, including 230V single-phase and 400V three-phase systems. It is important to distinguish this from "extra-low voltage," which applies to circuits not exceeding 50V AC, such as telecommunications, alarm systems, and data cabling.

While BS 7671 (the IET Wiring Regulations) is a non-statutory document, its role in UK law is fundamental. The Electricity at Work Regulations 1989 is a legal requirement under the Health and Safety at Work etc. Act 1974, mandating that all electrical systems are constructed to prevent danger. Authoritative sources like the Health and Safety Executive (HSE) regard installations that conform to the standards in BS 7671 as the most likely way to achieve conformity with these legal obligations. Therefore, selecting and installing the correct low voltage cables in accordance with BS 7671 is the accepted professional method for demonstrating legal compliance and fulfilling a duty of care, making it a critical aspect of professional liability and risk management.

General Purpose Low Voltage Power Cables

These cables form the backbone of electrical distribution, designed to transmit power efficiently and safely from a source to various loads. Their construction is determined by the balance between electrical performance, environmental resilience, and cost.

What Are The Main Conductor And Insulation Materials?

Conductor and Insulation Materials Explained

The most common materials are highly conductive copper or lightweight aluminium for conductors, and versatile thermoplastic (PVC) or robust thermosetting (XLPE) compounds for insulation and sheathing.

The choice between these materials represents a critical engineering trade-off based on the specific demands of an application.

Conductors:

• Copper (Cu): Industry benchmark for electrical conductivity. Flexibility and high conductivity allow for smaller conductor sizes for a given current rating.
• Aluminium (Al): For larger cables, provides a compelling alternative. While it is less conductive than copper (requiring a cross-sectional area approximately 1.6 times larger for the same current capacity), it is significantly lighter and often more cost-effective.

Insulation and Sheathing:

• PVC (Polyvinyl Chloride): Highly versatile, flexible, and cost-effective thermoplastic. Standard choice for general-purpose internal wiring.
• XLPE (Cross-linked Polyethylene): Thermosetting material with superior thermal stability (up to 90°C). Preferred for more demanding applications and underground cables.

What Are Armoured Cables Used For?

SWA vs AWA Cable: Why the Armour Material Matters

Armoured cables are used in applications requiring enhanced mechanical protection against impact, crushing, or abrasion, making them essential for external, direct burial, and heavy-duty industrial installations.

The distinction between Steel Wire Armour (SWA) and Aluminium Wire Armour (AWA) is a mandatory safety requirement dictated by the principles of electromagnetism:

Feature	Steel Wire Armoured (SWA)	Aluminium Wire Armoured (AWA)
Armour Material	Galvanised Steel	Aluminium
Magnetic Properties	Magnetic	Non-Magnetic
Core Application	Multi-core cables (all types)	Single-core AC power cables
Primary Function	High mechanical protection	Mechanical protection without overheating from eddy currents
Typical Use Case	Underground power to a factory (3-phase)	High-current single-phase supply to machinery

Critical Risk: Using the wrong type of armour for the application constitutes a serious design flaw that introduces a significant fire risk.