Energy blackouts

[adam2]

This is the report to which I referred.


https://eandt.theiet.org/content/articl ... ower-cuts/

It is also worth a study of the links in the first post of this thread. Though some years old, they are still relevant.

[BritDownUnder]

I am puzzled why Scotland could not black start with all the hydro around. I have only been to one 100MW hydro station, it was in New Zealand, and it had two smaller 300kW hydro generators for station black start to power the wicket gates and so on.

I can understand that a coal power station would be difficult to black start, I understand they are initially fired with oil until the boilers are at temperature.

Recently I was in a power station in South Australia where there was a blackout three years ago and the small 25MW gas turbine we were grid testing supposedly had a black start capability but the diesel generator was considered undersized as the hydraulic cranking motor drew too much initial inrush power for the diesel genset to handle. Apparently they had told the grid they could black start so they were going to do something about it (soft starter I think).

I was puzzled why networks with a lot of cables were more difficult to black start than overhead lines. Must be due to the reactive power vars difference or capacitive effect of cables.

I have never seen an air bottle starter system but it would probably be something to initially crank the starting gear i guess.

[adam2]

Large underground cable networks are slightly more challenging due to the capacitive charging currents involved as compared to overhead lines.

Larger or older diesel engines often started from air bottles. Special valve gear admitted this air to the cylinders in order that the engine in effect operated briefly as a compressed air engine. Once it was turning fast enough, the fuel supply was turned on and the engine ran as normal.

Once the engine was running, the air was replenished by either an electric compressor, or one driven from the crankshaft.
Sometimes a very small engine powered compressor was provided to refill the air bottles. This was small enough to start with a cranking handle.

Historically, air bottles were seen as more reliable than batteries. Batteries have however improved in recent years.
Air starting is still popular for marine engines.

[adam2]

Thought it worth reviving this old thread to add the link below which gives a bit of detail about black start requirements.

https://www.nationalgrideso.com/black-s ... quirements

There has never been a black start of the entire UK grid system. There WAS regional black start of London and the south east immediately after the great storm of 1987.
I recall that the voltage was unstable for the first hour or so.

Several areas of the UK were black started after the big freeze of 1963. The problem then was not the cold itself, that merely resulted in rota power cuts.
The sudden thaw immediately after the freeze caused many faults on overhead lines as dirty snow melted into conductive water.
In 1963 there was a lot more local generation than is the case today. Many coal burning plants that lost the grid connection were "tripped to house load only" That means the power station was kept running at low load simply to supply the power station ancillary equipment. Wasteful of fuel but does mean that full load can be taken almost instantly.