EMK:Grid

The Grid is the physical design of the lines and nodes.

Example of Grid Window

The grid is modelled as a single line between nodes, therefore if the physical grid has more than one line, this needs to be reflected in the values associated with the line. The physical aspects of the line, Resistance and Reactance are modelled to determine losses. Lines limits can be applied using 'Enforce' so constraints can be modelled.

Details Box (top of the window)

Name and Description	Used to identify and describe the Grid Resource
Base Voltage	Determines the variable losses that occur on a line through the formula: Loss = RZ2 / Base Voltage, where R is the per unit resistance of a line and Z the power flowing through the line in MW.

Lines Box

The Grid Lines Box provides access to details of the Lines connecting Nodes on a Grid. Lines can be added to, or removed from, the Grid Instance and their details edited.

Note: Within EMarket positive line flow (Node from to Node to) is an arbitrary convention. EMarket automatically adjusts for line flow direction at run time.

Line Box Fields

Line Name	Automatically produced from Node From and Node To fields
Node From	The code of the Node defined as the upstream Node when line flow is positive
Node To	The code of the Node defined as the downstream Node when the line flow is positive
Resistance	The per unit resistance of the line
Reactance	The per unit reactance of the line
Winter Limit (MW)	The maximum capacity of the line during the Winter period
Summer Limit (MW)	The maximum capacity of the line during the Summer period
Enforce	When set to Y the Line capacities are enforced during Runs. When set to N, EMarket runs with the Line unconstrained which means that the power flow can exceed the limit values in this table.

The Check Grid Configuration Button is used to ensure that all Nodes listed in the Grid Nodes Box are connected to the Grid and that there aren't any duplicate lines. An error message is returned if the Grid is not properly connected.

DC Lines Box

The Grid DC Lines Box is used to set the limits on DC Lines (principally for the HVDC link).

DC Lines Box Fields (Fields which are identical to the lines box have been omitted)

+Limit (MW)	The capacity of the line when the power flow is positive
-Limit (MW)	The capacity of the line when the power flow is negative

Note: Lines appearing in the DC Lines Box cannot also appear in the Grid Lines Box. You will be prevented from saving a Grid with Lines duplicated in this manner.

Nodes Box

The Grid Nodes Box contains the Nodes available for connecting the Lines in the Grid and determines the linkage between Node and Reserve Region which is essential for effective Reserves modelling.

Note: Reserves Node-Region mappings should not be confused with the Node-Region mappings (related to Demand) in the Regions Resource Editor - they have distinctly different purposes.

Nodes Box Fields

Node	A code representing a Node on the Grid
Region	The Reserve Region where the Node is located. New Reserve Regions can be mapped to Nodes simply by editing their Region field.
Resistance	This represents the per unit resistance between the retail supply Nodes and those on the Grid backbone and is used to model transformer losses on aggregated Grids. Full Grid models do not need resistance values, where aggregated grids are used resistance values may be needed to model losses.

Equations Box

The Grid Equations Box is used to model Equation Constraints associated with the Grid.

Equation Box Fields

Name	Used to reference the Constraint in Schedule Resources and Reports
Formula	The constraint formula expressed in the same format as used by Transpower.: For the Constraint to be effective the circuits used in the formula must have exact matches in the Grid
Winter Limit	The value (as calculated in each Tick using the formula) at which the Constraint will become effective during the Winter period
Summer Limit	The value (as calculated in each Tick using the formula) at which the Constraint will become effective during the Summer period

Comments

• Nodes need to be present before a line can be entered
• Individual line limits can be modified for defined periods using the schedule
• Individual lines can be entirely 'outaged' through the schedule
• Data can be copied directly from excel cells into cells in EMarket

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