2011 enquiries, reviews and investigations
Review of events of 13 and 14 December 2011
| Stage: II (Review) | Status: Complete | Date commenced: 22/12/2011 |
On 13 December 2011, circuit breakers at the Huntly power station tripped on protection, resulting in the disconnection of generation. 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.
The Authority has reviewed the operation of the wholesale market during and after the event on 13 December 2011. The review focuses 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.
Review of 26 September 2011 infeasibility situation
| Stage: II (Review) | Status: Complete | Date commenced: 28/09/2011 |
Trading period 16 on 26th September 2011 involved a confluence of several pricing and metering issues that together tested the process by which final prices are calculated. The review notes that but for an error made by the system operator in resolving the infeasibility, unprecedented prices would have occurred at some nodes in the lower North Island (up to $56000/MWh).
The high prices are a manifestation of numerically correct, but economically questionable outcomes of the pricing model. A conclusion of the review is that events on the 26th September be taken as a 'near miss' warning, and that urgent changes to some aspects of the Code are required. The review also recommends a generalisation of the high spring washer resolution process to mitigate other mechanisms by which extreme prices can be derived.
Review of August 2011 frequency keeping costs
| Stage: II (Review) | Status: Complete | Date commenced: 16/09/2011 |
The total frequency keeping costs during August 2011 were the highest since December 2009, when the system operator included a revised frequency keeper selection method in its new market system.
This review outlines the frequency keeping selection process and its shortcomings, which made it susceptible to unanticipated costs. A detailed analysis of the August 2011 frequency keeping costs is also provided to quantify the potential magnitude of this shortcoming.
Review of price separation during HVDC reversal
| Stage: II (Review) | Status: Complete | Date commenced: 29/08/2011 |
Following the introduction of the new market system project (MSP) by the system operator in mid 2009, the modelling practice for the HVDC in the final pricing schedule has changed. The new practice is to apply to the dispatch schedule, a maximum constraint of 0 to pole 1 or pole 2 when either pole is scheduled to operate below its minimum operating level in real time. If the constraints occur across a trading period boundary, it is also applied to the final pricing schedule.
This report analyses the possible impacts of the current practice on final prices and financial transmission rights.
Analysis of historical offer revisions
| Stage:II (Review) | Status: Complete | Date commenced: 21/08/2011 |
Under certain specified circumstances the Code allows generators to revise their offers up to two hours before the start of a relevant trading period. However, the Authority has observed instances of inconsistent generator offer behaviour, which has sent confusing information to other spot market participants.
The Authority has reviewed these historic offer revisions. This report discusses some of the issues around generator offering and describes a graphical representation of how a generator's offers evolve over time and a metric for quantifying the likely impact on the market, both of which the Authority intends to publish on an ongoing basis.
Review of high spring washer resolution issue with SFT
| Stage: II (Review) | Status: Complete | Date commenced: 18/08/2011 |
Prior to the introduction of the simultaneous feasibility test (SFT) in March 2011, security constraints were applied manually, with one constraint being applied to parallel lines. Since the introduction of SFT, different but very similar constraints can be applied to parallel transmission lines. The similar constraints undermine the ability of the high spring washer resolution process to mitigate extreme prices.
This report elucidates the underlying high spring washer resolution issue through analysis of some recent market situations.
Review of Stratford peaker commissioning 8 February 2011
| Stage: I (Enquiry) | Status: Complete | Date commenced: 09/02/2011 |
The system operator increased the North Island instantaneous reserve (IR) requirements from 08:30 to 15:00 (trade periods 18 to 31) on 8th February 2011. This was done to cover the additional risk to the system due to the commissioning of the new Stratford peaking units.
Dispatch of unscheduled generation: 23-27 January 2011
| Stage: II (Review) | Status: Complete | Date commenced: 01/02/2011 |
The Electricity Authority has released a report on events surrounding plant being constrained on in late January 2011, particularly Huntly Unit 5 on 23-27 January 2011.
On 11 February 2011, the Authority received a letter from the System Operator answering six questions asked on 1 February 2011.
On 22 February 2011, the Authority received a letter from Contact Energy expressing concern at the magnitude of constrained-on payments for January 2011.
On 23 February 2011, the Authority went back to the System Operator with an additional four questions. The System Operator sent the Authority a letter answering those questions on 28 February 2011.
On 2 March 2011, the Authority received a letter from Genesis Power answering four questions asked on 28 January 2011.
On 18 March 2011, the Authority received a letter from Mighty River Power expressing concern at the magnitude of constrained-on payments for January 2011.
The System Operator sends a daily report to the Market Administrator each day just after 7:00am. The daily report covers the previous 24-hour period and provides a comprehensive list of potential breaches of the code, adjustments to the pre-dispatch schedule, discretionary action, and block and station security constraint notices issued by the System Operator. The 26 January 2011 daily report is presented below as an example