Automated Under Frequency Load Shedding (AUFLS) Project

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What is AUFLS Background information
Timelime Industry involvement
ATR Consultation  

What is Automated Under-Frequency Load Shedding?

AUFLS is the acronym for Automatic Under-Frequency Load Shedding and describes the set of relays in New Zealand which automatically trip blocks of load, following a severe under-frequency event, to restore the system frequency.

Transpower as System Operator (SO) relies on these relays to prevent system collapse following under-frequency events which have the potential to cause a system black-out.

Under current Code arrangements, North Island distributors, and Transpower as grid owner in the South Island, must arm two blocks of load for AUFLS provision. The total load armed in each block must be at least 16% of the provider’s total network demand. Each Distributor must provide information that either complies with the technical codes or is reasonably requested by the SO, to assist it in planning to comply and complying with its principal performance obligations. Currently, North Island Distributors are required to provide this data annually, via submitting their Distributor Asset Capability Statement spreadsheets. In addition to SO providing regular reporting, following an Extended Contingent Event, the SO will complete analysis of the performance of the AUFLS scheme and request that Distributors provide specific AUFLS data.

Background information – Development of the AUFLS 4-block scheme proposal

Between 2010 and 2013, a project named Extended Reserves reviewed the current AUFLS arrangements and identified that the scheme could be amended to improve overall performance. The Electricity Authority (the Authority) has been working with the SO to develop a proposal for these amendments.

The proposal specifies transitioning the North Island AUFLS system from its current two block scheme to a four block scheme. This will reduce the size and increase the number of AUFLS blocks provided by distributors to two blocks of 10% and two blocks of 6% with rate-of-change-of-frequency (RoCoF) trip settings on the fourth AUFLS block.

Details of the proposal to implement a four block AUFLS scheme can be found on the Authority’s website at the following location:

Project Timeline

Transitioning to a four block scheme will take several years to implement. The first phase of the project is currently underway and is focusing on establishing a data portal for North Island Distributors to be able to submit their two block AUFLS data to the SO. This will allow the SO to baseline the current two block scheme which will then be used to develop a plan to transition to the new four block AUFLS scheme. The Authority aims for the transition to the four block scheme to be complete by end June 2025.

Ongoing Industry Involvement / Contact Us

The system operator will actively engage and support the North Island Distributors during the AUFLS portal roll-out to ensure all parties are ready to use the new AUFLS portal for the next AUFLS submission period starting January 2022. Support is complemented by training videos, and support documentation (refer ‘Relation Information’ section below).

The SO is also planning several webinars (in July, September and November 2021) where we will walk through the roll-out and will provide a demonstration of the portal and its functions.

You can send your queries regarding the project and register your interest for the webinars to the AUFLS Project Manager at Any technical queries can be sent to

ATR Consultation

The System Operator consultation on the ATR Document closed on 17 September 2021. 
The Authority has now approved the final version of the ATR Document. The ATR will be incorporated by reference into the Code, and come into effect from 21 December 2021.

Related information / Documentation

For more information on the AUFLS scheme, the AUFLS Data Portal, learning animations, FAQs, user guides and the configuration and load data templates see the AUFLS web page.