Over-frequency reserve is provided by generating units that can be armed when required and automatically disconnected from the power system due to a sudden rise in system frequency.
This could be due to an unplanned loss of a large industrial load or the tripping of the HVDC link.
We may enter into over-frequency reserve contracts with parties who can offer over-frequency reserve compliant with our technical requirements and the Code.
Over-frequency reserve is procured on a firm quantity procurement basis (via a monthly availability fee and/or a single event fee for specified generating units).
Over-frequency reserve costs are paid by Transpower as the HVDC owner (see clause 8.57 in the Code for details). For the 12 months to 31 October 2022, the costs for the procurement of over-frequency reserve were approximately $2 million.
Net purchase quantity assessment
We have assessed that the current over-frequency reserve quantities procured are sufficient to enable us to meet our PPOs.