Glossary

First things first - it is essential to understand that the NEM is operated on Australian Eastern Standard time (GMT + 10 hours) - which means no daylight savings. All data published by NEMMCO (and hence updated by NEM-Review) is stamped on this basis.

It is important that you are aware that, in real-time, the NEM operates in two different intervals:

• Dispatch (5-minute) Intervals
  NEMMCO dispatches the market on a five-minute basis.
  
  In doing so, NEMMCO takes generator's bids to supply, and assumes what the demand in each region will be at the end of the current five-minute (dispatch) interval to determine:
  • what each generator should be producing at the end of the five minute interval, and hence
  • the dispatch price.
  It should be understood that the dispatch data is data derived from the dispatch algorithm for the end of each dispatch interval. Specifically in terms of generator production, regional demand, and interconnector flow:
  • the data is an instantaneous value (i.e. MW rather than MWh); and
  • the data is not actual metered data, but rather derived from calculations.



• Trading (30-minute) Intervals Even though the dispatch process is operated on a 5-minute basis, commercially the NEM operates on a half-hour (trading) basis.
  
  The trading interval data published by NEMMCO is just the time-weighted average of the 6 x five-minute dispatch data points within a given trading interval. Hence, it is not until just after 25 minutes into a trading interval that the trading data for that interval can be known with certainty.
  
  The generators are paid the variable trading price for net production in the half hour, and wholesale market customers (and hence indirectly the energy users) pay the variable trading price for energy consumed in each given half hour.

The key point here is that, when referencing the data updated by NEM-Review, it is important that you are aware that the data is all trading data.

The following are the data sets supplied in NEM-Review:

• Pool Price
  The prices included in the NEM-Review package are denoted by NEMMCO as "RRP". NEMMCO defines this as follows:

  Regional Reference Price - the energy clearing price at the reference node of each region for the reported interval ... For trading interval information, this is the (actual) spot price.

  The trading price for the half-hour is the time-weighted average of the six dispatch (5-minute) prices set within the trading (30-minute) period. For instance, a trading price calculated at 13:25 (applying for trading between 13:00 and 13:30) will be the average of the dispatch interval prices set as follows:
  
  Set at 13:00 (for 13:00 to 13:05);
  Set at 13:05 (for 13:05 to 13:10);
  Set at 13:10 (for 13:10 to 13:15);
  Set at 13:15 (for 13:15 to 13:20);
  Set at 13:20 (for 13:20 to 13:25); and
  Set at 13:25 (for 13:25 to 13:30).



• Demand
  The demand included in the NEM-Review package are denoted by NEMMCO as "TotalDemand". NEMMCO defines this as follows:

  Total Demand can be summarised as the total non-dispatchable loads for each region. It reflects the price independent demand use by the NEMMCO dispatch engine (NEMDE) to calculate dispatch and pricing.
  
  In dispatch, total demand is calculated using the following formula:
  
  Total Demand =
  metered generation
  - metered dispatchable loads
  - allocated interconnector losses
  + demand forecast
  + aggregate dispatch error
  
  For trading interval information, this is the time-weighted average of the dispatch interval demands for the half-hour.
  
  Note: NEMMCO excluded Victorian smelters (950MW) from Victoria's demand in the first 2 years after market start.

• Interconnector Flow
  The interconnector flows included in the NEM-Review package are denoted by NEMMCO as "MWFlow". NEMMCO defines this as follows:

  The scheduled interconnector flow from the interconnector's defined sending end at the region boundary. Positive flow is given by the interconnector naming convention. The identifier indicates the direction of a positive value of power flow as follows:
  
  V-S-MNSP1 - From Victoria to SA (Murraylink)
  V-SA - From Victoria to SA (Heywood)
  V-SN - From Victoria to Snowy
  SNOWY1 - From Snowy to NSW
  NSW1-QLD1 - From NSW to Queensland (QNI)
  N-Q-MNSP - From NSW to Queensland (Directlink)
  
  For trading interval information, this is the time-weighted average of the dispatch interval flows for the half-hour.

• Unit Generation
  The generation included in the NEM-Review package are denoted by NEMMCO as "TotalCleared". NEMMCO defines this as follows:

  For a scheduled generating unit, this is the target gross electrical output of the unit for the dispatch interval. For a scheduled load, this is the forecast electrical consumption for the dispatch interval. For dispatch interval data, the target refers to the end of the five-minute interval. For example, calculation of the 06:35 dispatch interval commences at 06:00 using a snapshot of input data. Targets are intended to be achieved by 06:35.
  
  For trading interval data, the value is the time-weighted average of the dispatch interval targets for the half-hour ending the indicated time.

  Note that metered (sent-out) generation is what is used for payment purposes – however this information is confidential and is not released to the market (and hence can’t be updated in NEM-Review).

For the NEM-Review Silver Model, three additional data sets are provides, as follows:

• Available Generation
  NEMMCO also publishes the total available generation capacity for each unit for every trading period, as declared by each generator. This information is presented in NEM-Review in two ways:
  
  
  • For each individual generator (NEMMCO has named this “Availability”). NEMMCO defines this data as follows:
    

    Bid energy availability.

  • Aggregated for each region (NEMMCO has named this “Available Generation”). NEMMCO defines this data as follows:

    The available generation in the Region for the interval.

• FCAS Prices
  In order to balance the market in real time (i.e. within each 5-minute dispatch interval) NEMMCO procures Frequency Control Ancillary Services (FCAS) from those willing and able to supply it.
  
  There are a total of 8 commodities purchased, reflecting different times in which the service must be supplied, and whether the service is for raising the frequency (e,g. which would be required if a large generator tripped offline) or lowering the frequency (e.g. which would be required if a large load tripped offline).
  
  The total volume of trading across all 8 FCAS commodities is only approximately 1% of the total purchases of energy in the NEM. Hence, it is a small but vital part of the NEM.
  
  FCAS prices for each of the 8 commodities in each region are updated through NEM-Review Silver Model.



• Interconnector Losses
  As part of the dispatch process, NEMMCO calculates the losses that occur on each of the interconnectors and publishes this data. This is updated in NEM-Review Silver Model. For clarity, please note this data is not metered data, but instead is calculated within the NEMDE dispatch process.
  
  NEMMCO calls this “MW Losses” – and defines this as follows:

  Interconnector losses at cleared flow.

The following data sets are derived by NEM-Review from the aforementioned NEMMCO data:

• Number of Hours Run
  The number of hours when a unit's generation is not zero.
• Availability
  The number of hours when a unit's available generation is not zero.
• Number of Full Outages
  The number of times when a unit's available generation drops from some positive number to zero.
• Outage Length
  The number of hours when a unit's available generation is zero.