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Treatment for a longer life

Energy Transmission

Energy firms are seeking ways to prolong the lives of the UK's aging overhead power lines and pylons. Andrew Mylius finds out how one company is helping.

Blackouts last year in Birmingham and London put the wind up many in the UK power industry.

Following hard on the heels of grid collapse in the US, which left tracts of America without electricity for a day or more (NCE 21/28 August 2003), the UK cuts prompted regulator Ofgem to call an urgent investigation into the health of the national grid.

A fortnight ago the resulting report cleared National Grid Transco, which operates the UK's power distribution system, of blame for the power cuts.

But it is widely held that Britain's transmission infrastructure is fragile.

'Most of the existing system was built in the 1950s-70s. It is close on 50 years old and heading rapidly into old age, ' says Dave Chesney, director of EM 2, a new transmission asset management company formed by specialist power contractor Eve and consultant Mott MacDonald.

EM 2has been created in response to the growing delapidation of the transmission system. In the present tightly regulated climate, levels of investment are low - although Ofgem is expected to grant companies in the region of a 30% spending increase in its April 2005 price determination. Combined with the increasingly tough planning battles fought by electricity companies for permission to replace, let alone build new overhead lines, there is a keen interest in extending the life of assets already there.

In the past maintenance has been managed with gangs of painters working on pylons systematically, starting at one 'end' of the network and finishing at the other, says EM 2and Mott director Peter Black. But the advanced age of the network 'creates a market where you need to take more care of it the older it gets. In the past people were happy to leave it running merrily away but we're now seeing corrosion as major issue', he warns.

This is leading to a rethink of maintenance strategy, with pylons particularly at risk of degradation prioritised for steel replacement, corrosion treatment and painting.

Particularly at risk are steel structures exposed to salt spray near the sea, and those in industrial areas, where atmospheric pollution results in low level but persistent chemical attack.

'Pylons aren't going to fall over tomorrow, ' Black concedes, 'but they are approaching that day.'

By catching corrosion before it becomes a terminal problem, EM 2reckons five to 10 years can be added to the life of the average pylon. 'It's pushing back the replacement horizon by a good few years, which saves electricity companies millions, ' sums up EM 2and Eve director Stuart Lermont.

Small pylons cost £50,000£60,000 to build, depending on design and the terrain in which they are to be located, and large pylons anywhere from £600,000£700,000. There are 32,00033,000 towers, believes Lermont.

If the cost of replacement alone is not a strong enough case for extending the life of pylons, there is the unquantifiable cost of lost transmission time to take account of, should a line go down through pylon failure.

Prioritisation is being managed through a combination of timehonoured climbing and structural inspection, collation of existing data held by the owners of transmission infrastructure and - this is the new bit - physical and atmospheric modelling using software borrowed from the petrochemical industry.

Corrosion is a major concern to petrochemical engineers, who need to keep in check the degradation of steel in contact with aggressive agents.

'There are people out there with PhDs in rust studies, ' jokes Lermont. This knowledge translates effectively to the assessment and treatment of steel in all sorts of other environments, he notes.

EM 2's modelling involves inputting details of pylon design - there are some 120 different pylon models - age, data on the pylon's structural condition, and air quality and meteorological information. The output should yield information on the pylon's residual strength and life expectancy.

'This enables us to tackle repair and maintenance proactively rather than reactively, ' sums up Lermont. 'It's about the best means at our disposal of preventing future major outages.'

'It has taken us about two years to get to the point of launching EM 2, and we've started with a £2M a year business, ' says Chesney. 'The potential for what we are offering in the UK is pretty large, and we think there's an appetite for what we are offering in Europe and the US as well.'

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