The Scenario Analyser

Purpose

To examine the sensitivity surrounding any given Dispatch Factor.

The output of a dispatch calculation is entirely dependent on the values of the input data. For any one dispatch calculation some of the input data could have a wide range of values without affecting the end result. For other data items even a fractional change in input value could effect wide reaching changes in the output data. Using EMarketOffer in Scenario Analyser Mode you can examine the sensitivity of any Dispatch Factor within a single dispatch in the Presentation Interface.

NOTE: You can analyse Scenarios created from either Market or Forecast Data Source, however results will not be useful in cases where historical Offers are unavailable in the Market data.

Marginal Analysis

Purpose

To examine the sensitivity around individual Dispatch Factors using a marginal analysis technique similar to that used for calculating Nodal Prices in the Market.

Marginal Analysis mode allows you to investigate the impact of small changes to the inputs of the dispatch problem. The inputs which may affect dispatch are:

• Nodal Demand
• Offer Prices and Quantities (energy and reserves)
• The limits of various Constraints such as Circuit Capacities and Group Constraints.
• The setting of a number of Reserves-related parameters

Not all of these input values will have an impact on the dispatch solution. Those that do have an impact include:

• Demand values
• Offer quantities for Units on the margin (i.e. Units with Offer tranches which have been partially dispatched)
• Offer Prices for marginal tranches
• Limits for Circuit and Group Constraints which are constrained.

Marginal analysis is conducted by changing the value of a selected value by a small amount, re-dispatching and comparing the new dispatch figures to the original ones. Differences in the 'before' and ' after' dispatch results are highlighted on the Map and in the Display Area Information Grids.

Using the Scenario Analyser

>> To use the Scenario Analyser:

1. Place the Presentation Interface into Scenario Data Source mode
2. Load a single period Scenario into the Presentation Interface
3. Click the Analyse Button

The Main Window in Scenario Analysis Mode

1. The Scenario Functions Panel disappears
2. The Data Source Manager disappears
3. The Analyser Functions Panel appears at the foot of the Main Window Side Panel

The Analyser Functions Panel

The Analyser Functions Panel Appears at the foot of the Main Window Control Panel' whenever the Presentation Interface is placed in Scenario Analyser mode.

Features

Feature	Purpose
Item Type	Provides a selection for the Modelled Item you would like to examine for sensitivity
Field Name	Provides a selection list of Dispatch Factors related to the selected Modeled Item
Item Name	Provides a selection list of individual instances of the selected Dispatch Factor
Analyse Margins Button	Diplays the results of a marginal analysis based in the Presentation Interface
Done Button	Returns the Presentation Interface to Scenario Data Source mode

NOTE: Marginal analysis can only be conducted on one Dispatch Factor at a time

>> To display the results of a Dispatch Factor Marginal Analysis in the Presentation Interface:

1. Select the Modelled Item type of the factor you wish to analyse from the Item Type Selector
2. Select the type of Dispatch Factor you wish to analyse from the Field Name Selector
3. Select the factor instance from the Item Name Selector
4. Load the result of the factor analysis into the Presentation Interface by clicking the Analyse Margins Button

Marginal Analysis Dispatch Factors

Modelled Item	Dispatch Factor	Instance Example
Circuit	Capacity	ABY_T2.T2_A
Equation Constraint	Limit	TMU_Runback_Enabled_S_P_E
Node	Load	TMK1101
Reserve Region	Subtractor	N/A
	Base Risk	N/A
Unit	Offer Quantities (bands 1-5)	Offer Q1, BEN0162_BEN0
	Offer Prices (bands 1-5)	Offer P1, BEN0162_BEN0
	Reserve slopes for Primary and Secondary Reserves	HLY2201_HLY1
	Primary and Secondary Reserves Quantities	RsvSecQ1, HLY2201_HLY1
	Primary and Secondary Reserves Prices	RsvSecP1, HLY2201_HLY1

Viewing Analyser Results in the Map

Results can be viewed using the Map as described in The Map.

WARNING! A marginal analysis is run automatically on activating Analyse mode using the dispatch factor used in the last analysis. It is therefore possible to see apparent differences being highlighted on the map even before you have selected a dispatch factor to analyse.

TIP: In most instances any differences on initially entering analysis mode should be negligible. However finding a significant difference is useful information, it will certainly indicate that the dispatch contains at least one very sensitive factor and provides an initial place to start your sensitivity investigations.

Viewing Analyser Results in Information Grids

While in Analyser Mode Main Window and Secondary Information Grids display the results of the last marginal analysis as the difference between the value before (original scenario value) and after the analysis.

NOTES:

1. Change columns are highlighted in pale green and show the absolute value of the change.
2. The Price value represents the Price before marginal analysis (ie in the underlying Scenario)
3. The load column, highlighted in yellow, can be edited in this window but will have no effect on marginal analysis until Analyser Mode is closed and the Scenario is re-dispatched from the Scenario Functions Panel
4. All columns in this display can be sorted high-to-low or low-to-high

Viewing Analyser Results in Watch Windows

While in Analyser Mode open Watch Windows are updated with the value differences resulting from a marginal analysis in the same way the Information Grids are. All other Watch Window functions remain effective.

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