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Electrical outages. cyber attacks ?

aligarjon
What's the chances of the power outages and airport problems being cyber attacks.     Is that possible.   I would think so  ?


Gary

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    Thanks for the clarifications Alan - they make sense.

     

    No loads or generation were lost as a result of the line opening. Losses were as a result of the under-frequency excursion.



    I think I was fooled by the statement in the executive summary (I really should stop reading them!) that said (my emphasis) "The lightning strike also initiated the operation of Loss of Mains (LoM) protection on embedded generation in the area and added to the overall power loss experienced."


    If embedded generation was lost purely on frequency - which would have been seen equally right across the country - and as far as I can tell only some embedded generation was lost - then I guess it must have been down to slight differences in the trip settings on individual units (or tolerance in each unit's frequency measurement etc). If all units are intended to trip out on similar frequency changes then maybe only a slightly worse frequency situation would have led to a much larger proportion of embedded generation disconnecting - implying we might have been on the knife edge of a far worse situation?

     

    The reasons behind the trip of the steam turbine at Little Barford are not currently in the public domain.



    I guess you know more than you can say here! - I was just going by their public statement that it was "associated" with the lightning strike.


      - Andy.

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    Hi Andy,

    I wasn’t getting at you for your reply - it just seemed to have most of the questions I wanted to answer. I haven’t figured out how to copy and paste into quotes yet in this new software! It is likely (and perhaps a good job) that only 500MW vanished due to acceptable tolerances on the frequency measurement. 


    Regards,


    Alan.
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    I wasn’t getting at you for your reply



    Don't worry - I wasn't feeling in the least got at! (Personally I much prefer to be told when I've mis-understood something - usually it makes understanding everything else around it much easier!)


    I haven’t figured out how to copy and paste into quotes yet in this new software!



    What I do is paste what you want and then add something else (a space or a newline or something) then highlight just what you've pasted and hit the Block Quote button (looks like a 99 close double quote). If there's nothing after what you've quoted, then anything else you type (or paste) after it is treated as part of the same quote, which is a bit irritating. Adding the space or newline or whatever works around that.


       - Andy.
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    "Loss of Mains (LoM) protection on embedded generation in the area "

    I know that embedded generation, i.e. my solar panels, need mains as a voltage and frequency stabiliser and a source / dump for extra energy.

    I therefore asked my installer why two houses in the same street did not see each other as "mains" in the event of a power cut and his answer was that solar panels are set to try and run at about 52Hz. They can't as long as the grid is connected but as soon as the grid is lost the frequency rises and the units all trip.

    It would expect this to happen if a line was taken out by a lightning strike long before the auto reclose reconnected the supply but with my solar panels they would restart generating fairly quickly on restoration.

    Does anyone know how a wind farm reacts to suddenly finding it is generating more than the connected load?


    What I think all this shows is that it is impossible to test system stability and protection in a live situation. It can be mathematically modeled by clever people but probably not in sufficient detail to be sure of the way the system will react. All we can hope for is that lessons will be learned from this event which will improve the models.
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    Harry Macdonald:

    . . . What I think all this shows is that it is impossible to test system stability and protection in a live situation. It can be mathematically modeled by clever people but probably not in sufficient detail to be sure of the way the system will react. All we can hope for is that lessons will be learned from this event which will improve the models.




    System stability and protection are indeed both modelled. Protection can be tested by injection from suitable test kit, but the only way to test system stability is a full blackout, but no one wants that to happen. The data collected will be useful to partly validate the model. The best “practice run” the UK has had, was the storm.s of 1987, where the grid in the south-east was blacked out and rebuilt using the black start procedure. Of course in 1987 there was much more inertia on the grid. 


    Regards,


    Alan. 

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    Harry Macdonald:

    "Loss of Mains (LoM) protection on embedded generation in the area "

    I know that embedded generation, i.e. my solar panels, need mains as a voltage and frequency stabiliser and a source / dump for extra energy.

     




    The purpose of LoM protection (and in this it differs from UF, OF, etc protections) is not to protect the generator.  It is designed to detect if the generator is feeding an isolated part of the network which has become detached from the grid - islanded.  An islanded generator will still run but will subject any connected loads, your neighbours for instance, to a voltage and frequency which is uncontrolled and therefore potentially damaging.  So LoM protection is not to protect the generator, it is mandated to protect other consumers still connected to an islanded generator.


    The most common and effective method of detecting LoM for larger generators is by detecting rate of change of frequency (RoCoF).  This works because it's extremely unlikely, in the event of a network trip that leaves a generator still connected to some consumers, that the power output of the generator exactly matches the power demand of the loads.  So there will be a rapid change of frequency, either up or down depending on how big the islanded section of the network is.  It is possible to measure the fact that the frequency is changing rapidly long before it has changed enough to trigger OF or UF relays.  Until earlier this year the mandated setting of LoM RoCoF relays was at a rate of change of frequency of 0.125Hz/s, and that still applies to existing generators.


    One of the things demonstrated by the event earlier this month is that, as the inertia of the network falls, the entire grid can now experience rates of change of frequency approaching or exceeding 0.125Hz/s.  So the ability of RoCoF protection to correctly and rapidly detect an islanded situation is becoming compromised.


    Don't get me wrong - I'm not suggesting a return to the good old days of heavy coal burners so that LoM protection works properly.  We shouldn't be choosing the generation we build just to suit the needs of the grid.  We should choose the generation we build for more fundamental reasons, like saving the planet, and then adapt the grid to cope with that.  And one overdue change that is needed to adapt to the changing generation mix is a change in the mandated settings of LoM RoCoF relays. 

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    John,

    Very well said. The obvious conclusion that I see is that the setting of the RoCoF should be re-evaluated. Having spent most of my career dealing with ships I am aware of the frequency transients that occur when large loads are switched and the standards (e.g. IEC 60092, BS8450) and the Class Society Rules (e.g. LR, DNV, ABS, etc.) allow a 5% permanent deviation and a 10% transient deviation with a recovery time of 5 seconds, so obviously a 10% deviation has a minimum RoCoF of 2.0 Hz/s (from the initial excursion beyond the permitted 5% deviation down to 10% then back up to the permitted 5%). In reality the rate of change is much faster on the way down than during the recovery and so is probably around 10 Hz/s since the load switched is probably a relatively large percentage of the generating capacity (say 10%) and the system is designed to cope with this. It makes me think that doubling the present setting to 0.25 Hz/s would allow the system to function, but the problem then becomes "with what size of islanded section of the grid would we then fail to detect the problem?"

    The problem could subsequently become somewhat different as a small island of high inertia generators may then be more resilient to frequency changes than a much larger island of low inertia generators.

    Alasdair
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    "Protection can be tested by injection from suitable test kit"

    I know, I've done it many times but I suspect that there are conditions that cannot be simulated.

    I recall testing a large UPS system, 32MW for one building. We had done all the tests, we ended by connecting a 32MW loadbank (that was fun) and threw the main switch. All went well but, of course, in a real power cut our UPS system would be feeding all of the local area as well for the few milliseconds between loss of power and the main breaker opening. That couldn't be tested!

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    Harry Macdonald:

    ..., in a real power cut our UPS system would be feeding all of the local area as well for the few milliseconds between loss of power and the main breaker opening.




    Are you sure? How is the main breaker trip arranged? If the intention is it opens on the Under Voltage Trip then the UPS could stop it seeing the loss of power and you may be feeding the local area until the UPS grinds to a halt - which wouldn't be very long.

    Just a thought....

    Alasdair

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    " How is the main breaker trip arranged?"

    I never found out the details but I'm sure phase angle was involved so as soon as power was detected as being exported it would trip.

    But how quick that could be is another matter. Less than one cycle?

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