Challenges of HV and UHV underground cable installation
Where underground space is limited, HV and UHV cables sometimes need to be installed near each other. It’s a common challenge when bringing cables from off-shore wind sources to those on-shore, or improving the power output of a substation in the grid.
The closer the cables are to each other, the easier it is for heat to build up. The potential for hot spots increases, which can lead to damaged cables. Heat build up can also increase resistance placed onto the cables, reducing the total power output the cables can achieve.
Thermal resistivity of heat-conducting concrete
Traditional materials used in HV and UHV cable bedding and infill have a thermal resistivity of between 1.2 (K.m)/W and 2.7 (K.m)/W. The thermal resistivity of PowerCrete is 0.33 (K.m)/W, thanks to our exclusive use of a binder with extremely high thermal conductive properties.
Our specialised concrete mix allows effective dissipation of heat, reducing the likelihood of hotspots and associated issues. Underground cables bedded or infilled with this concrete will continue to run at a safe temperature, keeping electrical transmission efficient.
Aluminium VS copper conductors
PowerCrete doesn’t just enhance electrical transmission and installation efficiencies, but can unlock cost savings, too.
Copper is a metal widely used for underground cable conductors. With superior electrical conductivity and a high current capacity, it’s easy to see why. But copper is an expensive material, and when scaled for use in a large infrastructure project, it can be out of budget.
Aluminium conductors are an effective alternative that can be used in most applications. They’re more affordable than those made from copper - in some cases, copper is five times more expensive than aluminium - making them ideal for managing cost constraints in large renewable projects. While copper has better electrical conductivity than aluminium (by a factor of 1.64), it’s also around three times heavier, meaning aluminium is easier for engineers to handle.
The shift towards aluminium is also because of its lower levels of energy loss. Studies have compared energy losses when using a small copper conductor against a very large aluminium conductor. The former generated the most losses, showing how aluminium could bring about significant savings across both energy and cost.
Thanks to working with both copper and aluminium conductors, PowerCrete gives engineers the flexibility they need when it comes to cost considerations as well as heat loss and handling ease.
High levels of workability
When embedding and encapsulating ducts and cables, for instance, you need a heat-conducting concrete with a free-flowing consistency. We can adjust the workability of PowerCrete to meet the demands of your application. PowerCrete is usually supplied at a consistency of S4/F4, but we can tailor it to meet the specific needs of any project to allow easy placement and compacting for the best finish.
Suitable applications for PowerCrete
Our specialist concrete mix is ideal for HV and UHV underground cable installations across numerous applications, including:
- On- and off-shore wind farms
- Solar farms
- Nuclear power plants and modular nuclear reactors
- Substations
- Subsurface power infrastructure
- Data centres
- Battery storage facilities
PowerCrete in use: Hurst National Grid Sub-Station
In 2020, the National Grid started a seven-year underground rewiring project in South London. Many of the cables relied upon to transmit electricity around the area site have nearly reached end of life and need replacing. PowerCrete was selected as the heat-conducting concrete mix that would house and protect the new HV electricity cables in these deep underground tunnels to deliver enhanced reliability and power.
View the case study
PowerCrete in use: Offshore Inch Cape Wind Farm Landfall
Critical to Scotland’s renewable energy infrastructure is the Inch Cape Landfall project. It plays a significant role in transitioning the UK to low-carbon energy. At the landfall site, the project needed a robust and thermally efficient solution for cable burial. PowerCrete was chosen for the project, enhancing heat dissipation and structural integrity of the electrical infrastructure.
View the case study
Power range of thermally conductive bedding materials
PowerCrete is our heat-conducting concrete mix with the lowest rate of thermal resistivity, 0.33 (K.m)/W. Not all applications require such a low level - one of the other mixes in our Power range may be more suitable for your project.
PowerSand
Product type: Sand
Ideal for: Long-distance underground cable routes where future access may be needed
Advantages: Offers stability by accommodating minor ground movements
PowerSand CBS
Product type: Backfill material
Ideal for: Energy, utility, and rail projects
Advantages: Certified and ENA TS 97-1 compliant, and dissipates heat to reduce electrical resistance
PowerSand CBS Extra
Product type: Non-traditional stabilised backfill
Ideal for: Power cable installations
Advantages: Contributes to a reduced carbon footprint, making it a sustainable choice
PowerCrete
Product type: Heat-conducting concrete alternative for bedding and infill
Ideal for: HV and UHV cable installations
Advantages: Superior thermal conductivity, supports conductors of different sizes and materials, and helps to prevent hot-spots
Thermal conductivity & resistivity comparison
| | Thermal conductivity | Thermal resistivity |
|---|
| PowerCrete | > 2.5 W/(m.K) | 0.35 (K.m)/W |
| PowerSand CBS Extra | 1.33 W/(m.K) | 0.75 (K.m)/W |
| PowerSand CBS | 0.83 W/(m.K) | 1.2 (K.m)/W |
| PowerFill | 0.37 W/(m.K) | 2.7 (K.m)/W |
| CableGel | 1.2 - 2.0 W/(m.K) | 0.5 - 0.8 (K.m)/W |
| CableCem | 1.2 - 2.5 W/(m.K) | 0.4 - 0.8 (K.m)/W |
Power range brochure download
Order PowerCrete
For more information on using PowerCrete to protect underground electrical cables for your application or to place an order, please get in touch with our technical team via: concrete.technical@heidelbergmaterials.com.
