When the lights go out — what happens if the national electricity grid shuts down?
We’ve all seen disaster movies where cities lose their power. But how prepared would Great Britain’s infrastructure be in the unlikely event the national electricity system really shut down?
If the whole national high voltage electricity network — the grid — loses power, then individual power stations would need to be restarted before they can power up the country.
Power stations normally require an electrical supply to start up (a bit like a car needs a battery to power the ignition). But with a total electricity blackout, there is no centrally-connected electricity available at scale to restart the system. So it has to be rebooted from scratch.
The procedure is called ‘Black Start’. And it’s one the most important, yet little-known back up plans in the UK.
How does Black Start work?
The way Black Start works is actually relatively simple. Smaller power sources start ever-bigger ones, scaling up and up until the entire country is powered up again.
Some power stations simply do not have the ability to be the starting point of a system reboot. But some modern gas, pumped storage hydrobiomass power plants are able to restart rapidly on demand. This is why Drax Power Station in North Yorkshire — which supplies around 12 per cent of the UK’s renewable power– is a key part of today’s Black Start planning.
Drax’s auxiliary generating units consist of three gas turbines, which can be started from batteries. These would in turn generate enough power to restart one or two main generating units.
The restarted generating units would then be used as the backbone of an ‘island network’ — operating independently of the national grid — that would be grown by adding pockets of supply.
The generating units would match the speed and frequency to create normal grid conditions and to restore supplies fast locally.
Finally the affected area’s ‘island networks’ would be hooked up to each other so electricity can be distributed around the country with the reliability and stability we have become accustomed to.
Is Black Start ever needed?
The good news? There has never been a blackout so widespread that Drax has been asked to do a Black Start.
But that doesn’t mean that it will never happen. And it doesn’t mean the capability is not ever tested.
In October 1987, there was a regional Black Start in the wake of the powerful storm that hit the south of the country. The damage left Kent and Sussex disconnected from the National Grid — but thanks to Black Start contingency plans, most people barely noticed.
Kingsnorth Power Station restored power to the area and it ran independently, cut off from the rest of the Grid, until repairs enabled it to be connected up again.
Staying prepared
When the electricity market was privatised, there was a risk that nationwide plans such as Black Start could have fallen apart. To prevent this, formal contracts were put in place to continue to restart from scratch if necessary. Drax has one of these contracts.
This makes Black Start — and Drax — as important as ever. If a disaster scenario ever struck for real, the most important back up plan you’d never heard of (until now) would swing into action.
Read the full story about how we can restart the UK electricity Grid at Drax.com
