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Overhead lines, OLE or 'wires'...
We get a lot of questions on what that means, how do they work and how long it takes to fix etc.
Here's a thread which we hope will be useful to passengers.
Thread #DelaysExplained
Overhead line equipment – OLE – is the wiring and other equipment you can see above electrified railway lines. They look similar to electric pylons you see across the country.
Our overhead wires carry 25,000 volts of electricity to power electric trains.
OK - so I know electricity powers my train and how it’s carried, but HOW does my train get power from the overhead wires above it?A Pantograph!
Scroll below
A pantograph is fitted on the roof of electric trains. It acts like a spring and pushes a conductive "head" onto the underside of overhead lines. This allows electricity to flow into the train.
Delays occur when a problem affects the overhead wires or train equipment, requiring us to either slow down or stop services.
The disruption can be caused by just some of the following:
Power supply failures.
High winds blowing the overhead wires out of alignment, or vegetation onto OLE.
The train’s equipment due to a faulty component.
Birds landing on the equipment and causing a short circuit.
Extreme heat causing the wires to expand and sag
Problems trigger an alert in our control centre of an electrical 'trip' advising us to investigate.
If necessary, electricity is turned off while the cause of the "trip" is investigated. This can potentially take up to an hour depending on location. Not a quick job!
Engineers arrive out on site and begin repair, usually in a specialised MEWP (Mobile Elevated Work Platform) that allows us to work quickly at height. If the wires have fallen down, the solution is more complicated and a lot longer to resolve.
When the repairs are completed, careful measurements are taken to check it’s safe and compliant. The teams and equipment then leave the site and report the repairs. 
We then switch the electricity back on, services are restored and electric trains are able to run as normal.
Due to the nature of the repair work, it can take some time for services to recover and return back to normal.
How can we prevent OLE failures?
The New Measurement Train, A.K.A 'Flying Banana' regularly takes measurements of the OLE, while travelling at speeds of up to 125mph.
Any faults detected are picked up and fixed by engineers before there’s an issue.
One of the most recent innovations we’re using is a pantograph camera.
They’re mounted on top of passenger trains and our engineers review the footage to check for faults in the OLE.
Pretty cool!
Each OLE delay is different – but we do everything we can to fix it as quickly, and as safely as possible.
We know delays are frustrating and we do everything we can to avoid them.Thank you for bearing with us while we get you moving again.
https://www.networkrail.co.uk/running-the-railway/looking-after-the-railway/delays-explained/
