Power Blackout

As the working week finishes and the weekend is about the land, who knew a modest-sized gas generator and an off-shore wind farm falling off the grid would cause so much chaos. Well, it did and it left almost a million homes and businesses without power.

Just before 5 pm on 9th Aug 2019, the Little Barford gas-fired generator owned by RWE’s, which generates 740MW of power, disconnected from the grid leaving a shortfall. On its own, nothing compared to what happened next. Just minutes later, the ‘part-built’ Gigawatt Hornsea offshore wind farm fell off the grid too.

This 1.74 Gigawatt shortfall was just too much to supply quickly, as orders flew into every gas-fired, pumped hydro and nuclear power generator site in the UK for more power, the grid’s frequency fell down to 48.9hz, below operating thresholds. Anything above or below 1% of the standard 50Hz risks damaging equipment and infrastructure.

Typically, an order would also be sent to high demand customers, like factories, warehouses, large offices to reduce consumption. This works for slight peaks, however 1.74 Gigawatt was just too much to save, so the grid’s emergency safety system kicked in, disconnecting large chunks of the population in a rolling blackout to help the frequency stable.

This ranged from Plymouth in the Southwest new Newcastle in the Northeast and many places in between to evenly balance the drains and surges across the grid. Some saw 10 seconds without power, others saw over an hour, with traffic lights, trains and mobile phone masts being worst affected. Every train out of Kings Cross was cancelled and a Hospital in Ipswitch suffered a backup generator failure causing more chaos.

No major ISP saw outages as most sites have generator backup in N+1 resiliency. However many mobile phone masts are backed up with batteries. Very small batteries too, which saw outages to mobile signal across affect areas. This caused some concern over the security and reliability of networks and how well prepared the emergency services were.

It’s still early days to assess whether FTTC cabinets were affected as within 45 minutes, both power stations were back on-grid and over the course of the next hour or so, local grids became operational once again as things returned to normal.

Slightly off-topic, but talking point – if you were affected, let us know.


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