Page to be fleshed out, about the Semi-Scheduled category
(A) Summary of current arrangements
In short-hand, the operation of a DUID that is registered as Semi-Scheduled is part-way between the fully Scheduled category (with a very prescriptive set of requirements specified in the NEM Rules) and the Non-Scheduled category (where the plant can essentially run as it likes, without following AEMO’s dispatch targets).
A Semi-Scheduled plant essentially switches operations between two states:
|State||What the Semi-Scheduled plant is required to do|
|Semi-Dispatch Cap (SDC) flag is OFF||
In practice this covers the majority of dispatch intervals.
When the SDC is OFF, the DUID can operate as it likes without needing to listen to* the AEMO’s Dispatch Targets.
* Whilst this is true, in terms of the way the rules are written (i.e. the Semi-Scheduled plant Conformance Status is automatically set to ‘Normal’ when the SDC flag is OFF), there is still a cost applied indirectly to Semi-Scheduled plant operating away from their Dispatch Targets during this period – which comes about through recovery of Regulation FCAS costs using the ‘Causer Pays’ method.
|Semi-Dispatch Cap (SDC) flag is ON||
Historically this might have been a very low percentage of dispatch intervals – however in practice this is increasing for some Semi-Scheduled plant as a result of both:
1) For a Scheduled plant, the Target means what the name suggests (i.e. the unit needs to meet the ‘target’ or it is deemed Non-Conforming):
2) For the Semi-Scheduled plant, the Target is perhaps mis-named and would be better named as a ‘Cap’:
Because there are so many dispatch intervals in which a Semi-Scheduled unit can essentially ignore its Dispatch Target, there are many more larger deviations in ‘Raw Off-Target‘ experienced for Semi-Scheduled plant than there are for Scheduled plant. In various articles on WattClarity (such as this article of 5th May 2020) we explore some of the potential implications of this, as the energy transition continues.
(B) Chronology of evolution
Will add something in here, as time permits.
|13th December 1998
(Start of the NEM)
|31st March 2009||
From the 31st March 2009
The effect this had on the number of rebids submitted by wind farms that existed at the time (i.e. those then registered as Scheduled) can be seen in the chart included in this article here.
|When in 2019?||
In an effort to improve the functioning of the Semi-Scheduled category, suitably approved Self-Forecasts were allowed to substitute for the AEMO-developed forecasts in AWEFS and ASEFS.
Will flesh this out with a short history as time permits.
|Future?||There are other changes to the Semi-Scheduled category being explored by some parties.
Will add more here, as time permits.
(C) Other useful references
On this WattClarity ® site, any articles tagged with ‘Semi-Scheduled Generation’ can be found here.
Will add in other links to useful references as time permits…