Electrical outages. cyber attacks ?

“So in short a lightning strike on a distribution line had three effects”


No. The lightning strike was on a Transmission line, which has no directly connected consumers. 


“1. Tripped out the protection for that line (as intended), losing both loads and embedded generation in the area served, then the protection autoreclosed within 20s restoring the loads, but embedded generation has to wait longer before it's allowed to reconnect - so the load on the national grid increased by the amount of the embedded generation (500MW they say).”


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


“2. The spikes from the strike also caused two of the three interconnectors from a wind farm to trip out (not expected) - losing 737MW”


We know that an issue has been addressed at the wind farm, the information as to what it was is not in the public domain. We do know that the interconnector to the grid was not tripped, the issue was at one or more of the windfarm’s substations. 


“3. The spikes from the strike also caused one steam turbine at Barford Gas Power Station to trip out (not expected) - losing 244MW”


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


“The loss of the steam turbine knocked the combined cycle system out of kilter, so causing the two associated gas turbines to trip out within 90s - losing a further 397MW”


Yes, in so far as with the steam turbine tripped, the steam produced by the gas sets has nowhere to go, and either trip on high steam pressure, or need to be tripped by an operator. 


“So the grid was then out of balance to the tune of 1.9GW - while the grid has 'reserves' ready for only 1.0GW - enough to compensate for the loss the largest single generator - so the DNO's systems started load shedding.”


Yes. It is easier to shed 5% of the load and recover from it, which took under an hour on the day, than lose 100% and be in a true black start scenario. That is a difficult and time taking scenario, and has never (yet) been done in the UK. 


“Is it just me or does 500MW of embedded generation on one single distribution line sound like a lot”


The 500MW of embedded generation that tripped would be spread throughout the country. 


Regards,


Alan.

“So in short a lightning strike on a distribution line had three effects”


No. The lightning strike was on a Transmission line, which has no directly connected consumers. 


“1. Tripped out the protection for that line (as intended), losing both loads and embedded generation in the area served, then the protection autoreclosed within 20s restoring the loads, but embedded generation has to wait longer before it's allowed to reconnect - so the load on the national grid increased by the amount of the embedded generation (500MW they say).”


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


“2. The spikes from the strike also caused two of the three interconnectors from a wind farm to trip out (not expected) - losing 737MW”


We know that an issue has been addressed at the wind farm, the information as to what it was is not in the public domain. We do know that the interconnector to the grid was not tripped, the issue was at one or more of the windfarm’s substations. 


“3. The spikes from the strike also caused one steam turbine at Barford Gas Power Station to trip out (not expected) - losing 244MW”


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


“The loss of the steam turbine knocked the combined cycle system out of kilter, so causing the two associated gas turbines to trip out within 90s - losing a further 397MW”


Yes, in so far as with the steam turbine tripped, the steam produced by the gas sets has nowhere to go, and either trip on high steam pressure, or need to be tripped by an operator. 


“So the grid was then out of balance to the tune of 1.9GW - while the grid has 'reserves' ready for only 1.0GW - enough to compensate for the loss the largest single generator - so the DNO's systems started load shedding.”


Yes. It is easier to shed 5% of the load and recover from it, which took under an hour on the day, than lose 100% and be in a true black start scenario. That is a difficult and time taking scenario, and has never (yet) been done in the UK. 


“Is it just me or does 500MW of embedded generation on one single distribution line sound like a lot”


The 500MW of embedded generation that tripped would be spread throughout the country. 


Regards,


Alan.