EMK:Getting the Best out of EMarket

The key to effectively managing and organising the vast amount of data that is produced by EMarket, is disciplined record keeping of Run ids or Resource Versions. Experience has also shown that the best overall result is obtained from the model when there is an appreciation of its underlying theory and construction. This certainly helps in interpreting its output and using the results. If you have a question it can be forwarded to the Energy Link helpdesk: helpdesk@energylink.co.nz

Non-Supply Generators

At times there will be conditions where there is insufficient generation either nationally or one side of a constrained line. Therefore it is essential that non-supply generators are configured at various Nodes.

It is suggested to have at least one non-supply Generator, however it is recommended that there is one located in each major Region of the grid which could be partially cut off from other Regions by a line constraint. These will usually provide enough generation despite any Grid constraints that develop. It generally provides enough geographical distribution to reduce serious distortions of Grid flows and perhaps unusual price differences across the grid.

More non-supply generators might be needed if a number of constraints could be active, as might occur with far-future runs or with Generator outages.

Far Future Runs

The accuracy of any DCPF could decrease significantly in far-future runs because Demand growth could either push lines to near their limit for substantial portions of a year or load lines to the point where line losses are excessive and rather inaccurate. Care should be taken with far-future runs to thoroughly investigate Grid flows to determine which lines, if any, are likely to suffer this problem. Check the line constraints Report to determine which lines, if any, are reaching their load limits.

Investigation could indicate that some lines should have their capacity increased and resistance reduced to improve the results. This effectively means anticipating an upgrade to the Grid which requires careful thought and judgement. It should be kept in mind that there are always two alternatives in this situation as either the line can be upgraded or new generation can be added to alleviate the Grid congestion.

Location Factors

The location factor of a Node is defined as the price at the Node divided by the price at some arbitrary reference Node. In other words, location factor expresses the relative price difference across the grid from a common reference point.

It is easy to concentrate on one aspect of the model and find later that other aspects are not working well. A typical example is to concentrate on the price at the reference Node, only to find that location factors are unrealistic in other Regions.

Location factors in many parts of the country are very sensitive to the patterns of generation.

Location factors are driven mainly by losses, except when line constraints are active. This usually occurs during outages for repair or maintenance, or when very high transfers occur on a line. Losses, in turn, are driven by Grid flows which are driven by the pattern of net injection, i.e the nodal injection minus nodal off-take. Thus the pattern of generation is as important as the reference prices.

A typical problem with location factors will occur when two large stations are generating in the wrong pattern in EMarket when compared to the actual market.

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