Formal complaint to Rulings Panel against system operator

On 5 June 2024, the Electricity Authority lodged a formal complaint with the Rulings Panel for an alleged breach of clause 30.1B of the Policy Statement (incorporated by reference into the Electricity Industry Participation Code 2010) by the system operator.

The alleged breach relates to a requirement of the system operator to correctly apply security constraints, regardless of whether or not the information on the Transpower website about the power system stability limits or security constraints is complete or up to date.

On 28 January 2022, Transpower (as the system operator) built a temporary manual constraint scenario in its modelling tool to manage a low hydro level situation in Southland. As part of that process, an associated input was modified that resulted in Tiwai loads being renumbered.

As a result of the renumbering, the system operator’s tool did not recognise the load as Tiwai and scaled it up in its simulations, as with other Southland loads.

This resulted in the voltage stability constraint being set at a lower value and binding in the real time system when it should not have.

The incorrect constraint subsequently bound in 102 trading periods, causing price separation between Southland (grid zone 14) and the rest of the grid.

The Rulings Panel determines breaches of the Code and may make appropriate remedial and other orders under section 25 of the Electricity Industry Act 2010.

See regulation 29 Notice of Rulings Panel referral, which publicises and provides reasons for the Authority’s decision.