Page last updated at 07:40 GMT, Wednesday, 28 May 2008 08:40 UK

Tripping the light fantastic

By Rebecca Morelle
Science reporter, BBC News

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Ian Cotton gives a tour of the high voltage facility - and reveals what happens when lightning strikes inside the lab

"This might make you jump a bit," warns Ian Cotton.

It is near pitch-black in the viewing room where we are standing; a soft red glow exuding from a warning light above the door barely cuts through the darkness.

A klaxon sounds, and, suddenly, a giant flash of lightning bolts through the air, accompanied by a deafening crackle, lighting up the room for a fraction of a second.

Every day, the National Grid High Voltage Laboratory at the University of Manchester generates electricity that can reach millions of volts.

The hangar-like facility is packed with enormous pieces of equipment: transformers, generators and the odd huge aluminium sphere stand tall. A glass-fronted viewing room, where experiments can be safely watched, is adjacent.

It is one of the few places in the UK where scientists can work with huge voltages at first-hand.

Lightning tests

Ian Cotton, a senior lecturer at the University of Manchester's School of Electrical and Electronic Engineering, says: "We do a lot of lightning protection work here."

Electricity is taken straight from the mains, at the UK's standard 240 volts, but a towering impulse generator then ramps it up to a massive two million volts - creating a voltage that can be used to see how lightning attaches to objects.

Lightning lab
The impulse generator can boost electricity to two million volts

On a regular basis, equipment prone to lightning strikes is brought into the facility.

"We do routine testing of aircraft nose cones - or radomes," explains Dr Cotton.

Aircraft are mostly made out of metal - meaning that any lightning strikes are conducted towards the tail. But as the nose cone contains a radar, which would be blocked with a metal casing, this component of the aircraft is made out of glass fibre.

But, according to Dr Cotton, this has a drawback: "If lightning hits [glass fibre], it would blow apart and incinerate - and you cannot have that on a plane.

"This means that they have to have special lightning protection - diverter strips that are often made from segmented pieces of metal.

"And we are able to test how well they can guide the lightning to a safe place in a lab like this."

Wind turbines also make a regular appearance in the lab.

Dr Cotton says: "If you went back 15 years, early types of wind turbines had no lightning protection in the blades. When the blades were hit, they would blow apart into smithereens.

"This is obviously bad for the economics of operating a windfarm - and of course for public safety."

Now the blades have a protection system built in, which is especially important as wind turbines can be placed offshore where repair is difficult.

Dr Cotton says: "We are constantly checking that these lightning protection systems work well and we are working on improving their resistance to lightning."

Buzzing power lines

Another giant transformer towers inside the test area.

This one boosts electricity to 800,000 volts - about double the voltage that power lines or substations carry.

"We use this generator to carry out experiments on all of the types of equipment that are used on the power system," Dr Cotton says.

"If you own lots of overhead lines and cables, you want to understand how they are working and when they will fail."

Electrcity apparatus
All kinds of electrical apparatus are tested at the lab

Of particular interest are insulators - the devices that resist the flow of electrical current to make electrical apparatus safe. You normally see these carrying the conductors on an overhead line.

The team feeds them with electricity to investigate where and when any strains and weaknesses appear.

In the lab, when the voltage is turned up, the insulators turn a gentle shade of blue as corona discharge - the buzzing noise you sometimes hear around power lines - begins to emit.

They then begin to spark violently as they reach the point at which an electrical breakdown occurs.

Ageing equipment

Equipment is tested under lots of different conditions.

Dr Cotton says: "We have a salt fog chamber, where insulators go into a very, very salty environment - it is akin to a heavily polluted one - and they degrade very quickly.

"We can also simulate extremes of light - we have a bank of UV lights that show us how plastics change in sunlight."

Apparatus in high voltage lab
You cannot make anything 100% perfect, but the better you can make it, the more chances you have of keeping the lights on
Dr Ian Cotton, University of Manchester

Testing how equipment fares as it ages is key for power companies.

Most of the electrical infrastructure in the UK was installed in the 1950s - and at the time, was given a shelf life of about 40 years.

A decade after this life limit, some have expressed concerns of an impending electricity crisis should any equipment begin to fail.

However, regular tests carried out at this facility, and at other similar labs around the country, show that the equipment is continuing to function well and shows little decay.

Dr Cotton says: "The problem is, when a lot of this new kit was designed, no-one really knew how to predict its lifespan - 40 years was a pretty arbitrary number."

He adds that it is important to keep on testing the apparatus, a process known as condition monitoring - and this is really where high voltage labs come into their own.

He explains: "Electricity is important in our everyday lives; now people take it for granted - you switch on a light and you don't really think about how it gets from a power station to your house.

"But that process is a complex path of overhead lines, cables and substations, and all of them have to be working well virtually all of the time.

"You cannot make anything 100% perfect, but the better you can make it, the more chances you have of keeping the lights on."


SEE ALSO
What to do in a thunderstorm?
05 Jul 06 |  Magazine
How planes survive lightning
28 Apr 05 |  Magazine

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