Transmission & Distribution Technology
point that cable cleats earn their crust. In contrast, circuit breakers typically interrupt the fault after three or even five cycles by which time, if the cleats are underspecified, the cables will be long gone, meaning the expensively assembled circuit breaking system will never been given the opportunity to be tested.
Should a buyer see a specification for 4,000 of our Emperor cleats it is natural that they may look elsewhere to find a better per unit price. Te issue though is that the specification is particular to the project and the product, having been set according to the strength of the cleats and their spacing along the cable. As such any change in the type and strength of cleat will result in a change in the numbers required, which in turn will have a knock-on effect on price. Terefore, if a buyer is intent on changing the specification they really need to look at overall as opposed to per unit cost.
Fig. 2. The Zagorskaya Pumped Storage Plant in Russia.
Tis change is not going to take place over night, and so specifiers and engineers need to take steps to aid the correct specification of cable cleats. Perhaps key is being aware that levels of cable protection can be enhanced by selecting only products that are classified in section 6.4.4 of the International Standard. What this means, is that the cable is guaranteed to still be intact and operable after a short circuit, as opposed to just the cleat. Unfortunately, eradicating the problem isn’t that
simple. Most specifiers and engineers are diligent when it comes to system design. Where the problems really begin is when the specification reaches the buyer. At which level there isn’t the technical understanding of cleats and instead the focus is far more on cost.
“Without cleats, the dangers are obvious – costly damage to cables and cable management systems, plus a risk to life posed by incorrectly or poorly restrained live cables.”
Looking at things from a budgeting point of view, it is fair to stay that certain initial costs would be increased by adopting practices that ensure the correct specification of cable cleats. But if you consider the kind of sums involved, in terms of time, materials and manpower, in replacing an entire cable management system due to a short circuit occurring and causing irreparable damage it’s easy to see the point of the additional expense. Ellis is the only leading manufacturer in the electrical industry that focuses solely on cable cleats. Its products are used extensively in the power industries. Recent successes include the UK’s National Grid’s London Power Tunnels project, the Zagorskaya Pumped Storage Plant (PSP) in Russia’s Moscow region and the new Ledvice Power Plant in the Czech Republic. ●
Richard Shaw, Magazine Director, Ellis
Fig. 4. Ellis’ Emperor cable cleat, which is used to great effect in power installations throughout the world.
Fig. 5. Testing times – Ellis’ cleat undergo short circuit testing.
Fig. 3. The new Ledvice Power Plant in the Czech Republic. 14
www.engineerlive.com
Richard Shaw is magazine director of Ellis, Malton, North Yorkshire, UK.
www.ellispatents.co.uk
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