Stage: II (Review) Status: Complete Date commenced: 22/12/2011

This resulted in an under-frequency event and the operation of the first block of automatic under-frequency load shedding (AUFLS) in the North Island.

We reviewed the operation of the wholesale market during and after the event on 13 December 2011. The review focused on pricing effects, such as discrepancies between real time and final pricing, suppression of prices that was at odds with the severity of the event, and ambiguities in the determination of some final prices.

The review recommends further consideration be given to improving the pricing process, so that participants can respond confidently to pricing signals when the system is in a stressed state.

Overview of events of 13 and 14 December 2011

Review of events of 13 and 14 December 2011