Specifics of the frequency excursion (well outside the NOFB) on Thursday 6th November 2025

With respect to today’s frequency excursion, we’ve already noted:

• the ‘Major spike in mainland frequency, on Thursday 6th November 2025’; and
• our current hypothesis for a data glitch as the cause – in ‘Was that a data glitch that saw lunchtime ‘Market Demand’ ramp in Victoria by 1,812MW?’

In the first hasty article, the pre-canned visualisation of our high-speed readings of system frequency are constrained to the bounds of the NOFB, and the frequency clearly climbed outside of them.

So I’ve extracted our data at 0.1 second cadence and present this 4-hour time range here:

The time period of interest:

• Spans the range:
  • ~12:30 (when the frequency appears to break out of the PFR deadband)
  • to ~12:50 (when the frequency returns within the PFR deadband
• Peaking at 50.229Hz at 12:45:21.2 (NEM time);
• With the frequency outside the NOFB:
  • from 12:34:31.9Hz (first at 50.15Hz)
  • to 12:47:04.3 (back consistently below 50.15Hz)

We’d need to check with ‘next day public data’ (time permitting on a future day) to see who was enabled for Contingency Lower FCAS at the time, because it does look like there was some resistance to the procession above 50.15Hz.