A quick article to record the following snapshot from our in-office high(ish)-speed (100ms) frequency readings for the NEM Mainland on Tuesday 12th November 2024:
We can clearly see the frequency drop outside of the lower bound of the NOFB, which would have triggered Contingency FCAS response.
Briefly speaking – it looks like there were two coal units drop offline in relatively quick succession, contributing to the drop:
We see two email alerts triggered by the ‘Notifications’ widget within ez2view:
1) The Stanwell unit 2 came offline from 136MW (i.e. around its Minimum Load) in the 5-minute period prior to 10:35 NEM time
2) The Yallourn unit 4 tripped form higher load (357MW) about 10 minutes later (in the 5-minute period prior to 10:45 NEM time
… I would expect the vertical drop in frequency in the chart above lines up with this larger (and potentially more sudden) trip from Yallourn unit 4.
Finally (in this article) the AEMO published MN120305 suggesting some problem in the connection to the grid, perhaps not within the unit itself?
‘——————————————————————-
MARKET NOTICE
——————————————————————-
From : AEMO
To : NEMITWEB1
Creation Date : 12/11/2024 10:55:18
——————————————————————-
Notice ID : 120305
Notice Type ID : POWER SYSTEM EVENTS
Notice Type Description : Emergency events/conditions
Issue Date : 12/11/2024
External Reference : Non-credible contingency event – VIC region – 12/11/2024
——————————————————————-
Reason :
AEMO ELECTRICITY MARKET NOTICE.
Non-credible contingency event – VIC region – 12/11/2024
At 1041 hrs the Yallourn No 1 220 kV bus and Yallourn Unit 4 tripped.
AEMO did not instruct load shedding.
AEMO has not been advised of any disconnection of bulk electrical load.
The cause of this non credible contingency event is not known at this stage.
Manager NEM Real Time Operations
——————————————————————-
END OF REPORT
——————————————————————-’
That’s all for now…
PS1 … Yallourn 4 tripped … then also Yallourn 2 and Yallourn 3
Turns out, whilst typing up the above there were other developments – as summarised in this snapshot of the ‘Generator Outages’ widget in ez2view, complete with overlay of three different Yallourn-focused alerts from the ‘Notifications’ widget within ez2view:
As noted here, Yallourn unit 4 was the first unit to trip at the station … but then that was also followed by trips of Yallourn unit 2 and Yallourn unit 3.
Guardian reporting a boiler tube leak unit 3, and trip triggered when isolating that unit. Perhaps a mistake in a switching sequence?
Do deviations from 50 hertz down affect mains powered clocks and is the effect cumulative?