Sharp mainland frequency drop, with trip of CPP_4 on Sunday evening 26th October 2025

Quite topical, given these ‘Two *big concerns* that we urge the Nelson Review panel to (re)consider (with respect to Invisible Responses) following review of the Draft Report’ – was the sharp drop in mainland frequency observed in our higher-speed monitoring (i.e. at 0.1 second cadence):

This drop in frequency was shortly followed (when the next Dispatch Interval rolled around) with this ‘Notification’ widget alert from ez2view to show that the Callide C4 unit had tripped from 420MW in the 5 minutes to 18:36 (NEM time) on Sunday evening 26th October 2025:

That’s all for now…

PS1 update from CS Energy on Monday 27th October

Thanks to Matt for his comment here., which points to the update from CS Energy  I thought it would be worth copying in the text of what CS Energy said here:

‘Unit C4 at Callide Power Station tripped and came offline at approximately 6.30pm yesterday evening (26 October) following a storm and lightning strike to Powerlink Queensland’s Calvale switchyard which connects Callide to the power grid.

Callide’s other generators Units B1 and B2 are online. Unit C3 is offline until mid-November for a planned major overhaul which started in August.

Assessment of the full impact of the storm is ongoing, but Callide Unit C4 is currently forecast to return to service this Friday 31 October at 6pm.

Powerlink has confirmed the Calvale feed is available for operation. Our engineers are reviewing the turbine and boiler historical data to ensure there are no issues in returning the unit to service as forecast. We have also received some storm damage to the C3 and C4 cooling towers. Our preliminary investigations show that the damage is non-structural.’