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October 20, 2019, 10:24:19 pm *
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Author Topic: Power outage strands trains  (Read 4018 times)
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« Reply #45 on: September 11, 2019, 10:39:23 pm »

The frequency disruption was for a relatively long duration, some put this down to the lack of inertia on the National Grid due to the loss of so much heavy rotating generating plant

There is a figure for "inertia" in those reports - 200GVAs, which I suspect is about the usual level at the moment. A useful number to tuck away in your toolbox (ideally with a proper definition). NG do have research going on on the use of batteries to provide "synthetic inertia", but I could see no mention of that in the reports. They do talk about campaign to reprogram small (embedded) generators to trip on a RoCoF (rate of change of frequency) of 1 Hz/s rather than the current value of 0.125 Hz/z. That would have kept a lot more of that generation on line. They say that will take three years, but some of the other evolutionary changes do seem to be going rather slowly.

On more point that I don't think was addressed directly was the cliff-edge effect of generators tripping due to RoCoF. The 1st July event (described in the main report) saw 1,000 Belgian MW lost, and the system coped - just.  The 9th August event was initially not much larger, but was just big enough that the reserve could not cope and, for want of enough power, the frequency fell. That led to enough extra generation disconnecting itself that the power shortfall suddenly became very large. Changing the RoCoF limit does address this, of course - eventually. 

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« Reply #46 on: September 11, 2019, 10:52:46 pm »

The Times has pointed out that the makers of the turbines farmed at Hornsea - who presumably supplied the control software - were Siemens Gamesa (59% owned by Siemens). They didn't labour the point, but ... Before anyone starts on about "German software", Gamesa's engineering centres are in Denmark, Spain, and India.

Incidentally, the Hornsea system is new to the grid - the three modules went live on 1/2/19, 30/4/19, and 15/7/19 - so a certain amount of optimisation based on observation is to be expected. In which case, why had they not picked up the tendency for oscillatory power flows (as in the example ten minutes before the outage) already?

« Last Edit: September 13, 2019, 10:42:05 am by stuving » Logged
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