Underground Cable Design

As an expert delivery partner, Groundline Engineering supports the full lifecycle of Underground HV and EHV cable systems.

We combine rigorous engineering, practical construction insight, and standards driven assurance to help clients achieve reliable and future ready underground networks. Our collaborative approach ensures challenges are addressed early and outcomes are aligned from design to commissioning.

What We Do

Cable Design up to 500kV

Customised high-voltage cable design for specific industrial, tunnel, aviation, utility, generation, transmission, and renewable energy applications (wind, BESS, solar).
Design optimisation for power transmission efficiency.
Cable system earthing and bonding designs.

System Engineering

Detailed system studies for voltage levels, load requirements, and fault tolerance capability.
Cable route planning and route optimisation, including city, urban, rural, and agricultural underground installations.
Engineering of overhead, submarine connectivity to landfall, and underground cable systems.

Testing and Certification

Facilitation of high-voltage testing arrangements for performance validation (impulse, dielectric, and thermal modelling).
Compliance with IEC, IEEE, CIGRÉ, client, and local standards.
Quality assurance and reliability.

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How We Compliment Existing Teams and Deliver Results

We have experience in all aspects of the power lines industry; from 11kV to 500kV+, new builds to refurbishments, condition assessments to asset management, site support and design verifications to project management – we’ve done, and can do, it all.

Our team has worked around the world, in incredibly diverse and difficult environments; from remote, dry deserts, to wild, wet rainforests, urban cities, to cyclone-prone prairies - no matter what your challenge, we understand what’s required.

The Result: Predictable, Reliable, Defensible Outcomes

Predictability: Fewer late changes, clear decisions early, and stable scopes your delivery partners can rely on.
Buildability: Designs that reflect real installation conditions, reducing workarounds, delays and construction risk.
Reduced workload: Your PMs, designers and consultants spend less time chasing interfaces and more time delivering.
Clear, defensible decisions: Documented rationale and audit‑ready evidence that protects project and personal reputation.
Stakeholder confidence: The presence of credible underground expertise accelerates approvals and smooths regulatory engagement.

Our Work

Underground Case Study

Delivering a reliable and efficient solution for the new 132 kV cable circuit

Groundline Engineering partnered with the client to deliver a new 132 kV underground cable circuit, providing end-to-end engineering support from route development through to installation and commissioning. The project required close coordination with stakeholders and careful management of technical interfaces to ensure a safe, compliant, and constructible solution.

By combining detailed system design with practical installation guidance, Groundline helped derisk delivery and enabled the successful introduction of critical high-voltage infrastructure into the network.

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Our Underground Experience

Underground

Brownfield

Sub Sea

Greenfield

Airport

Heathrow Airport Terminal 5 and Airport Expansion Programme

Heathrow airport Ltd covering the installation of 30+major substations and 800kM of 33/11kV cabling in a subterranean network of tunnels, pit and duct networks in a square kilometre.

Teesside 33kV Substation and Connection to Off Shore Wind Farm

Cable design and Substation installation contractor for the 33kV connection and cable system routes to the Teesside offshore wind farm beach head joint transition locations.

Bramley 275kV Substation Additional Cable Circuits

Managing the Cabling Design support and interface between the Utility and cable installation Supplier.

Deeside 400kV Substation and Deeside EHV Testing Centre

Consulting the Design, Cable design and installation contractor for the cable system works and various test centre installations.

Pyle 275kV Substation New Install Additional Cable Circuits

Managing the greenfield Cabling Design and the interface between the Utility and cable installation supplier.

Bein & Tuirc on shore wind farm Mull of Kintire 48 Turbines

Cable systems, design, and Electrical Site Manager, managing Hyder Infrastructure Ltd Cable System Design and Substation design teams.

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Our Expertise

Introducing Roger Key

General Manager - Underground Cable Engineering

Roger Key brings nearly 60 years of experience in HV and EHV cable systems design and delivery, leading complex power infrastructure projects up to 400 kV. As General Manager at Groundline Engineering, he provides technical leadership across cable and substation engineering, with a strong track record supporting major utility, aviation, and renewable energy projects. Roger is widely respected for his practical expertise, collaborative leadership style, and ability to deliver safe, reliable outcomes on high risk, high value schemes.

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Underground HV/EHV Cable Design