High voltage cables (or HV cables) are essential for modern power transmission, enabling electricity to be transported safely and efficiently across long distances and demanding environments.
From renewable energy infrastructure and rail networks to underground power systems and offshore installations, HV cables support critical electrical infrastructure worldwide. But many people still ask: how high voltage cables are made, and what allows them to handle such extreme electrical loads safely?
At Custom Designed Cables, we manufacture high-performance cable solutions engineered for reliability, durability and compliance. Through expert cable design and precision manufacturing processes, we create bespoke cable solutions for demanding applications.
In this guide, we explain what high voltage cables are, how they work and the key stages involved in the HV cable manufacturing process.
What are high voltage cables?
High voltage cables are specialist electrical cables designed to transmit electricity at voltages above 1kV. They are commonly used in power transmission and distribution systems where large amounts of electrical energy must be transferred efficiently and safely.
Unlike standard electrical cables, HV cables are engineered with multiple protective layers to manage electrical stress, minimise power loss and withstand harsh environmental conditions.
Where are HV cables used?
High voltage cables are used across a wide range of industries and infrastructure projects, including:
- Power transmission and distribution networks
- Offshore wind farms and renewable energy systems
- Underground urban infrastructure
- High-speed rail and transport systems
- Marine and subsea power transmission
- Industrial facilities and data centres
- Oil rigs and specialist defence applications
Many of these applications require specialist harsh environment cables capable of resisting moisture, chemicals, abrasion and extreme temperatures.
As renewable energy and electrification continue to grow, demand for reliable HV cable systems has increased significantly.
Components of high voltage cables
What cables are made of defines their use and specific properties. High voltage cables are constructed using multiple engineered layers, each designed to support electrical performance, insulation and safety.
Conductor
The conductor carries the electrical current and is typically made from copper or aluminium due to their high conductivity.
Conductor shield
A semi-conductive shielding layer reduces electrical stress between the conductor and insulation.
Insulation
The insulation layer prevents electrical discharge and contains the high voltage safely within the cable. Proper insulation is critical for operational safety and long-term performance, which is why understanding the benefits of wire insulation is so important in HV cable manufacturing.
Common insulation materials include:
- XLPE (cross-linked polyethylene)
- EPR (ethylene propylene rubber)
Advanced wire insulation processes also help improve thermal stability and environmental resistance.
Insulation shield
This layer helps maintain a uniform electrical field and safely directs fault currents.
Metallic screen
Usually made from copper or aluminium, the metallic screen provides grounding and protection against electromagnetic interference (EMI).
Bedding & armour
Additional bedding and optional armouring protect the cable against moisture, mechanical stress and environmental damage, particularly in underground or subsea installations.
Outer sheath
The final outer sheath protects against water, UV exposure, chemicals and physical abrasion. Learn more about cable sheathing and cable jacketing and how they improve cable durability.
How do high voltage cables work?
High voltage cables work by transmitting electrical energy at elevated voltages while reducing energy loss over long distances. Increasing voltage allows electrical current to be reduced, which lowers resistive heat losses and improves transmission efficiency.
To safely manage these high electrical loads, HV cables rely on carefully engineered insulation, shielding and thermal management systems to prevent breakdown and maintain reliable operation. Depending on the application, high voltage cables may be installed:
- Overhead
- Underground
- Underwater or subsea
Certain installations may also utilise specially engineered flexible cables where movement, tighter routing or vibration resistance are required.
How high voltage cables are made
Understanding how high voltage cables are made involves looking at a highly controlled engineering and manufacturing process.
1. Cable design
The process begins with detailed cable design, where engineers determine:
- Voltage requirements
- Operating environment
- Thermal performance
- Flexibility and mechanical strength
- Compliance standards
This stage ensures the cable is engineered for its intended application.
2. Material selection
Manufacturers then select suitable materials for:
Material choice directly impacts cable durability, conductivity and environmental resistance.
3. Conductor manufacturing
Copper or aluminium conductors are produced through:
- Wire drawing
- Stranding processes
Stranded conductors improve flexibility and electrical performance as part of the wider cable manufacturing process.
4. Insulation & extrusion
Semi-conductive shielding and insulation layers are applied using precision cable extrusion processes to ensure consistent performance and reliability. For HV cables, XLPE insulation is commonly cross-linked to improve thermal and electrical performance.
5. Metallic screening & protection
The metallic screen is added to improve grounding and EMI protection, followed by bedding materials and optional armour for mechanical protection.
6. Outer sheathing
A durable outer sheath is applied to protect the cable from environmental exposure, chemicals, moisture and UV damage.
7. Testing & quality control
Every HV cable undergoes rigorous testing to ensure compliance with international standards. Testing typically includes:
- High voltage testing
- Mechanical testing
- Thermal testing
- Insulation resistance testing
- Partial discharge testing
This ensures long-term reliability and operational safety.
Why quality matters in hv cable manufacturing
High voltage cable failure can result in major operational disruption, safety risks and expensive downtime. For this reason, HV cable manufacturing requires strict quality control, advanced materials and precision engineering.
At Custom Designed Cables, we combine technical expertise with fast, reliable manufacturing to deliver bespoke cable solutions for demanding applications.
We offer:
- ISO 9001:2015 quality management
- UL & CSA approved options
- Bespoke cable design and manufacturing
- Technical consultation and support
- Fast turnaround times
Whether you need support understanding how high voltage cables are made or require a custom HV cable solution, our team can help. Get in touch today for tailored advice.
Frequently asked questions
What are HV cables?
HV cables are high voltage electrical cables used to safely transmit electricity at voltages above 1kV across power networks and infrastructure systems.
What insulation is used in high voltage cables?
Common insulation materials include XLPE and EPR due to their excellent thermal stability and electrical insulation properties.
Where are high voltage cables used?
HV cables are used in power grids, renewable energy systems, underground infrastructure, transport systems and offshore installations.