Under the National Electricity Rules, Scheduled and Semi-Scheduled units need to finalise bids for the following Market Day by 12:30 the day before (this is sometimes talked about as ‘Gate Closure’).

At this time, the unit’s 10 x Bid Bands are fixed for the following day, but the volume offered in each of those bands for all Dispatch Intervals (both now, and into the future of predispatch) can vary – using a Rebidding process.  The specific nature of the .

1st July 2021 – future It is worth noting that, in conjunction with the introduction of 5 Minute Settlement, the AER has introduced updated Rebidding Guidelines.

Documentation is available from the AER website here – including:
18th Sept 2019 = this “Draft Guideline for consultation – Sept 2019”, with written submissions required by 16 October 2019.
27th Nov 2019 = this “Rebidding and Technical Parameters Guideline – Final Guideline November 2019” , which becomes effective from 1st Oct 2021.

In conjunction with these AER Guidelines, the AEMO also published this document “Format and Validation for Energy, FCAS, and MNSP Bids and Offers” on 1st November 2019.

28th Feb 2017 – 30th June 2021 In February 2017 the AER published a revised version of the Guideline to replace the previous (December 2009) version. The release of the revised Guideline (and accompanying final decision) marks the end of a consultation process which began with a consultation paper in September 2016 followed by a draft decision in December 2016. The AER notes that they took issues raised in submissions to the consultation papers into account in arriving at their final decision.

The revised Guideline became effective from 28 February 2017.

Documentation is available from the AER website here – including the “Rebidding and Technical Parameters Guideline – Feb 2017”.

Note that this guideline provided some updates to the requirements established in 2009 – however it was the guideline of 2009 that provided a large step in the formalization of guidelines for rebidding in the NEM 

1st Dec 2009 – 27th Feb 2017 On 25 September 2009, the AER published the preceding version of the final Rebidding and Technical Parameters Guideline.
(a)  This version outlined the detail that needed to be be contained in a rebid reason submitted to the Australian Energy Market Operator (AEMO).
(b)  In addition, it covered several related areas associated with the bidding and rebidding of technical parameters.The AER recognised that compliance with the new Guideline would require a change to the business practices of many participants.  The revised Guideline became effective from 1st December 2009.Documentation is available from the AER website here – including the “Rebidding and Technical Parameters Guideline – Dec 2009”.—It’s also worth noting that, in this period (on 10th December 2015) the AEMC made a final rule to enhance the arrangements that govern generator’s offers in the wholesale electricity market.  The final rule amended the relevant provisions in the National Electricity Rules as follows:
(a)  The current requirement that offers be made in good faith will be replaced by a prohibition against making false or misleading offers.
(b)  Any variations to offers will need to be made as soon as practicable.
(c)  A requirement to preserve a contemporaneous record of the circumstances surrounding late rebids will be introduced.These changes were assessed in the AEMC project known as ‘Bidding in Good Faith’.
13th December 1998 – 30th Nov 2009 The initial 11 years of NEM operation incorporated the operation of the National Electricity Code Administrator (NECA) as the predecessor to the Australian Energy Regulator (which was established in July 2005).

With respect to discussion about Bids and Rebids on WattClarity and elsewhere, readers might be interested in the following:

Category of Rebid In the 2017 Guidelines, the AER required rebids to be attributed to one of the following categories:
Category “P” for Plant Reasons
Category “A” for AEMO Forecast or Dispatch Change
Category “F” for Financial/Commercial Reasons
Category “E” to Correct an Error
Form of Rebids –
‘Well Formed’ and
‘Not Well Formed’
The AER’s February 2017 Rebidding Guidelines requested participants to compose their rebids in a specific format for submission.

HHMM {space} Category {space} DDD…D

In the Generator Report Card 2018 we wanted to parse all the rebids made by generators (particularly since this guideline came into effect) in order to understand how many were made in each Category, and also for each plant type.

To do this we coded an algorithm that would parse all the bids using a strict interpretation of the structure of the rebid above and were surprised to find that the vast majority of rebids were ‘Not Well Formed (Strict)’.

By loosening the algorithm (i.e. taking into account the common types of failure modes of bids that we saw) we were able to successfully parse the Category and Time from the majority of rebids – however there were still a sizeable number of rebids that did not even pass that test, and were classified as ‘Not Well Formed (Loose)’.

This was discussed in this article from February 2019, and in more detail in the Generator Report Card.

Number of Rebids In the Generator Report Card 2018 we trended the number of rebids over time (by plant type and category).  This was discussed in this article from February 2019, and in more detail in the Generator Report Card.