EMO:Getting Good Data

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When solving EMO to reproduce dispatch solves from SPD (i.e. solves done by SPD when calculating final prices), or to look at what-ifs, it is essential that you have good data feeds into EMO. The following are our recommendations, and tips.

When comparing the market to EMO dispatch solves, always keep in mind that there are differences between what actually happened in the market and what EMO solves.

This arises for three main reasons:

  1. Dispatch is based on forecast demand whereas SPD solves for final prices with metered half hourly demand.
  2. Frequency keeping stations operate within their respective frequency keeping bands and not at exactly their dispatched MW values.
  3. The large hydro systems are generally allowed to block dispatch, under which they are given their station dispatches but they can change individual station outputs as long as the total system output equals the total MW dispatch for the block (the exception is when a block is split by a line constraint within the block). As a result, you will often see one station in a block up and one down by the same amount relative to the dispatch given by EMO.

The above is based on the assumption that you set EMO up to access actual generation data (from SCADA on em6) from your database for use in Market View mode. You could also choose to extract generator dispatch from the daily SPD data files available on the EA web site, in which case the agreement between EMO and the SPD generation data will be much better.

You also need to make sure that you have EMO download the latest data files from our web site, by going into File>>File Inputs and clicking on the "Check for New Files Box". The data that we make available for EMO is extracted from the SPD daily data files on the EA's web site, which is the data used by the Pricing Manager for final pricing. However, it is easy to end up working with the wrong set of inputs because these files come out in different versions, so you need to make sure that you are using the latest version that matches final prices.

Demand Data Changes with Introduction of DCLS Feb-15: The GXP daily demand data available on WITS, which we typically recommend you to use for demand data in EMO, has changed slightly. This data is based on the demand data actually used in SPD to solve for final prices, so is in principle what we need to produce accurate solves in EMO.

However, the introduction of Dispatch Capable Load Stations (DCLS) into the market has caused this data to become slightly less accurate than it was prior. It appears the GXP daily demand does not include the demand associated with a DCLS, for example at Kawerau. As a result, using this data in EMO leaves you short of demand and consequently you won’t find it easy to match your EMO solve to the market (e.g. as a starting point for an EMO Scenario).

For avoidance of doubt, please note that the DCLS demand data (e.g. at KAW0113) is still in the Transpower SCADA available on em6, so if you use SCADA data in EMO, then this is not an issue for you.

It is currently up to EMO users to source their demand data for use in EMO. At Energy Link, we have changed our approach: the GXP daily demand data is also available in the SPD daily final pricing files from which we extract reserves and constraint data (the data that EMO downloads from our web site under the File>File Inputs menu item). Also in these files is the demand at any DCLS, so we are working on a solution for our own use which will extract the GXP daily demand data and the DCLS data from the SPD daily final pricing files and store it in our demand database. We’re happy to share the details of this with you.