Hornsea Wind Farm Onshore Substation, North-East Lincolnshire, UK

Project Overview

Hornsea Wind Farm is situated in the North Sea 75 miles off the east coast of England. Construction of Hornsea One started in January 2018, and the first turbines began supplying power to the UK national electricity grid in February 2019.

At the time of construction it was the world’s biggest offshore wind farm, covering an area the size of more than 58,000 football pitches and designed to produce enough green energy for more than a million homes.

The electricity produced by the turbines is transmitted via undersea cables to one of three large offshore substations. From there, the cable comes ashore at Horseshoe Point in North-East Lincolnshire. It then continues through an underground cable to a high-voltage onshore substation in North Killingholme, where it connects to the UK National Grid.

The cable connection of the offshore platforms requires reactive power control, which makes the use of variable shunt reactors necessary. These are housed in bunds as a secondary containment system to mitigate environmental and safety risks.

Dura Composites worked with clients Ørsted and Balfour Beatty to provide phenolic GRP Dura Grating bund flooring which addressed the key challenges of traditional steel grating systems while meeting stringent safety and performance standards.

Addressing the limitations of steel grating with a phenolic GRP solution

The purpose of the bund is to provide safe and practical access to the plant while effectively preventing the spread of burning oil. To achieve this, its components must possess adequate strength, durability, and fire resistance.

Although steel-punched grating can restrict oxygen flow and aid in extinguishing fires, it presents several practical challenges. These include complex earthing requirements, a limited lifespan, and the difficulties associated with regular inspections.

For this reason, Dura Composites collaborated with our clients to provide a phenolic GRP Dura Grating system to address the shortcomings of steel grating which was tailored to the substation’s requirements.

Key features of the phenolic GRP pultruded grating 50mm T-Bar Dura solution

In terms of fire resistance, phenolic GRP has been rigorously tested and validated under USCG E-119 standards. Unlike other materials, it does not liquefy when exposed to fire. During testing, the grating successfully endures temperatures of 927°C for a duration of 60 minutes without failure, highlighting its exceptional resilience.

This solution met the high-performance standards of the project at the time of installation, boasting a 33% open area for drainage while complying with stringent safety and performance criteria.

These include the UK fire safety standards:

• BS 476 Part 7 Class 1 (Surface Spread of Flame)
• BS 476 Part 6 Class 0 (Fire Propagation)
• BS 6853:1999 Annex D8.4 (Smoke Emission Test).

Additionally, it adheres to the following international standards:

• ASTM-E84 (Flame Index 10, Smoke Index 135)
• ASTM-E119 (Fire Resistance)
• ASTM-D635 (Zero Burn Rate)
• ASTM-D2394-2011 (Static Slip Resistance 0.93, Dynamic Slip Resistance 0.82).

Durability was another key feature of the phenolic GRP, offering exceptional resistance to wear and tear. This reduces the frequency of replacements and minimises long-term maintenance costs, making it a cost-effective solution over time.

Finally, the ease of installation enhances its appeal. The GRP panels were installed on steel beams and securely fixed using Dome Washers and G-Clamps. This ensured a stable and reliable installation process, further underscoring its practical benefits.

In certain projects of this type, it is worth noting that the bund may also include a layer of 20mm single-sized washed rounded gravel, with a depth ranging from 75mm to 300mm. For calculation purposes, the air volume within the gravel, which can accommodate any spilled material, is considered to be 25% of the gravel’s total volume.

We take great pride in developing and providing innovative composite product solutions that enhance security and support the dependable operation of future modern power grids. The installation of Dura Composites’ phenolic GRP pultruded grating bund flooring at Killingholme Onshore Substation for the Hornsea One Wind Farm represented a major step forward in substation safety and operational efficiency. Developed collaboratively with our clients, our solution overcame the limitations of traditional steel systems by improving fire resistance, streamlining maintenance, and facilitating better access to equipment.

Joe Hunt

Industrial Sales Manager at Dura Composites

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