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UK Grid problems 9th Aug

UK Grid problems 9th Aug

UK Grid problems 9th Aug

The BBC is reporting widespread blackouts in London and the SE and I can see that a lot of emergency generation has started up (suggesting low frequency cut in). It'll be interesting to hear what happened and how low the frequency got. This is at least the 4th low frequency event so far this year.

Does anyone know any more details?

RE: UK Grid problems 9th Aug

Mbrooke: Another power outage for your record.

A preliminary estimate indicates that around 1 M people were impacted by the power outage in the UK.

Should be noted that some of the utilities involved in the power outage in the UK also own assets in the US such as National Grid (NG/former Niagara Mohawk) and Western Power Distribution (PPL in the US).


RE: UK Grid problems 9th Aug

@EnAppSys tweeting that it sagged to 48.814 Hz, alongside a fuel mix change plot that shows pumped storage kicking in to compensate, then being replaced by interconnect imports.

RE: UK Grid problems 9th Aug

From discussion on social media among ex-CEGB staff in the UK, something caused the CCGT plant at Little Barford to drop about 650MW off the system followed closely by Hornsea wind farm dropping a further ~800MW off the system. The big pumped hydro stations are fast to load up, but not that fast - the initial response has to come from machines already sync'd which have room to open their governors further or to over-fire their engines to maintain output as the frequency falls. The transmission system protection operated as intended to prevent either a system split or overall system collapse by dumping load from the system.

The UK system doesn't have many big high inertia machines left on the system as the last of the 1960's-vintage coalers retire - there's only the nukes and the largest single-shaft CCGT machines left of any real size - so the frequency fell really quickly, so fast that the generators charged with providing frequency correction couldn't increase firing fast enough to catch it. The inverters on the wind turbines just track the system frequency as it falls - they can't return stored energy into the falling system in the way that a large rotating machine does.

RE: UK Grid problems 9th Aug

National Grid do publish historic frequency data, so it will be interesting to look at this. unfortunately they publish it some months in arrears:


Losing all of Little Barford is a surprise, since I assume it has duplicate step up transformers to 400 kV, so it might have been a 400 kV bus fault.

The subsequent loss of Hornsea is interesting, I assume that was because of ROCOF or Vector shift mains failure protection.

Vector Shift is being phased out in the UK (not a joke) because of perceived mal-operations (at least in the UK):

"On several occasions, it has been suspected that a transmission system fault that did not result in islanding resulted in the inadvertent tripping of embedded generation plants by their LoM (Loss of Mains) protection. A definite event was recorded on 22 May 2016 following a single transmission circuit fault. Further investigation of this event showed that a significant number of embedded generation plants had tripped as a result of the operation of VS protection. This event resulted in a loss of infeed and a frequency excursion that was bigger than that which was anticipated."

New protection settings are being used and there is a lot of work making this retrospective.
As Scotty says, wind generation. in particular, essentially has no inertia (because they are connected via inverters) so the system inertia is falling as the historic coal stations are being closed. This can result in potentially larger frquency excursions as may have been the case of yesterday’s event.

Well at least the transmission system load shedding worked, otherwise they could have lost the whole GB synchronous area!

RE: UK Grid problems 9th Aug

What is ROCOF and Vector shift and how does it work? I'm bad with acronyms and names LOL.

RE: UK Grid problems 9th Aug

Does this have anything to with that old joke about Lucas and the temp of English beer winky smile

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RE: UK Grid problems 9th Aug

ROCOF is Rate Of Change Of Frequency, which is what ScottyUK meant in regards to the machines can load up, but not that fast.
ROCOF is meant to be able to distinguish between slower changes in frequency due to load changes, versus abrupt changes due to loss of generating capacity.

EDMS Australia

RE: UK Grid problems 9th Aug

Thanks for the details.
Little Bradford generation loss - even if it is 400kV bus fault, should it cause loss of both units?
I thought it is the practice to segregate the units, each unit connected to different busbar.
OR am I mistaken, it is only a single 650MW unit at Little Bradford!!

RE: UK Grid problems 9th Aug

The big ones are AC generators on a constant speed turbine. But also they convert to DC and back to AC to sync with the grid.

Similar to solar you can alter the power factor by +- 0.1 if you are having issues.

I am just a owner of a small 9.61kw solar plant but a mate in Scotland has a big turbine on his dairy farm.

The grid engineer that deals with him says the problem with these inverter systems is they only pump real power and the reactive has to be dealt with by the old school generators. So especially with loads of self producers and users it can knock the power factor hugely out for a site.

My power factor goes to poo when the heat pump kicks in when the solar is producing. 8.6kw ground. It's fine at night 0.9. Luckily its only out for under 10 seconds. If it was more that 20 seconds I would be automatically cut off from the grid.

He uses heatpumps as well on the farm which is why the subject came up when I installed my solar system. So I got an energy meter which also gives power factor from the start. Most solar plants they don't put them in until you get a battery. He has solar on his roofs as well and 44kw of high voltage battery's. He also has poo loads of led lights which apparently don't help.

I will state now I only have a mech engs worth of knowledge on AC so I can see the issue but don't know what the implications of this feature of inverters on the big picture.

But I would be extremely interested to find out from someone that does have a clue. Thinking about bringing my solar farm up to my 3p 32amp fuse limit.

RE: UK Grid problems 9th Aug

Another power outage in the UK.
The demolition by the implosion of cooling towers of a disused power station’s caused a power outage in Oxfordshire area on Sunday AM. Scottish and Southern Electricity Networks (SSEN) said material and dust related to the demolition had struck a 33 kV overhead power lines that affected 49,000 homes. Power restored a few hours later.


RE: UK Grid problems 9th Aug

On 9th Aug incident, initial information was Gas fired power station tripped first but, today I see in the news that it is actually Wind power plant that tripped a few seconds prior to Gas fired plant.
I wonder why this confusion??

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