UTS 21 April 2009

UTS claim

Contact Energy submitted a claim at a UTS occurred on 21 April 2009.

The claim was about how spring washer prices were calculated and alleged that a UTS occurred around the final prices for certain trading periods on that day.

Our investigation

Contact Energy submitted a claim that a UTS occurred during trading periods 37 and 38 on 21 April 2009.

We delayed publishing the final prices while we investigated.

During these periods, there was a planned outage of the Mangamaire-Woodville circuit. Due to high demand, the system operator temporarily increased the limit on a transformer (WIL T8) to handle more load.

Later in the day, the transformer was at risk of overloading and was removed from service, which led to a high spring washer price situation.

A “spring washer” is the term used to describe prices that are caused by the flow of electricity around a loop from a constrained circuit in the electricity grid. Prices on one side of the constraint are usually quite high while prices on the other side of the constraint are relatively low. A “high” spring washer is when the price differential across the constrained circuit is high.

Spring washer pricing calculations are valid solutions from the scheduling, pricing and dispatch model.

The pricing manager and system operator confirmed that all calculations and processes followed the Electricity Governance Rules 2003.

Our decision

We found that a UTS did not occur, as the situation did not threaten trading on the wholesale market for electricity and the pricing processes were carried out correctly.