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Providing secure support for 400kV underground cables

06 June 2014

Cable saddles and accessories manufactured by Ellis Patents are being used to secure high voltage cables throughout 32km of tunnels under London as part of the National Grid’s London Power Tunnels project.

A section of the tunnel between St Johns Wood and Kensal Green Substations - part of the London Power Tunnels 400kV project - showing the cable installed on Ellis Patents Centaur saddles and secured using Ellis Patents short circuit straps
A section of the tunnel between St Johns Wood and Kensal Green Substations - part of the London Power Tunnels 400kV project - showing the cable installed on Ellis Patents Centaur saddles and secured using Ellis Patents short circuit straps

The cable saddles were specified in 2012 in a record £1.5m order for the Yorkshire-based cable cleat manufacturer. 

“While it’s always great to secure a new specification, especially such a large one, it’s even more rewarding seeing the product installed and being used for the purpose for which it was designed,” says Ellis managing director Richard Shaw.

In the case of the London Power Tunnels, Ellis secured the specification from S?dkabel – the German manufacturers of the cables being installed in the National Grid tunnels – as a result of a design inspiration that saw them deliver a product that overcame a serious safety issue surrounding the restraint of HV cables up to 400kV with a diameter range of 100 to 160mm. Richard Shaw again:

“At the time we designed Centaur neither the British nor European Standards took into account cleats on HV cables of this size. This meant those specifying for such jobs were very much in the hands of the manufacturers, who in most cases simply provided warranties for their products.

“The problem with this was that none of the products available had been short-circuit tested, and so the warranties were based purely on calculations and mechanical tests. As such there was no proof the saddle cleats being used would withstand the most testing elements of the job they’d been specified for.” 

Before launch, Ellis put its new heavy-duty extruded aluminium product through the most rigorous of testing procedures. Using cable manufactured by ABB in Sweden, the company shipped the Centaur cable saddles and ABB cable to the Netherlands where they were tested to 163kA peak and 63kA rms for one second, in both three-phase and phase-to-phase fault scenarios.

“We invested well over £100,000 in designing, developing, testing and bringing Centaur to market,” adds Mr Shaw. “At the time this was the largest amount we’d ever invested in one new product, but we did so with confidence that it had the potential to solve a major safety issue and fill a gap in a growing market sector – a confidence that was quickly proven to be well-placed.” 


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