EMarketOffer uses two broad types of data:
Static Data: Static data describes the Items Modelled in EMarketOffer (e.g. Generator maximum capacity).
Dynamic Data: Dynamic data describing the state of the Modelled Items defined by the static data and changes rapidly over time, typically by Trading Period (e.g. Nodal Price)
Terminology
EMarketOffer's data design consists of 'things' (or items) included in the model, and the characteristics of those 'things'. In this manual the 'things' are called Entities and their characteristics are called Traits. Traits may be static or dynamic.
For example the Circuit Entity can have the static Traits of Start Node and End Node, and the dynamic Traits of Powerflow and Loss by Trading Period.
NOTE: : Static data is not permanently fixed and may, at times, be quite changeable, but within the context of EMarketOffer it is not necessary to be able to track such changes down to the Trading Period level.
Modelled Entities
Four broad categories of entity are modelled in EMarketOffer:
| Entity Type |
Relate To
|
- System
|
- The physical Transmission System
|
- Market
|
- The routine operation of the wholesale Market (Offers, Load, Price)
|
- Commercial
|
- Generation Companies and their retail and hedging operations
|
- Geographical
|
- Physical points and regional positioning
|
System Entities
The following table lists and describes the System entities modelled in EMarketOffer.
| Entity |
Description |
Attribute (Trait)
|
|
System Node
|
- Any point in the NZ Transmission System to which a Circuit can be connected
|
|
|
Substation
|
- One or more System and/or Market Nodes located at a single geographical location
|
|
|
Circuit
|
- A branch (Circuit) conducting power on the NZ Transmission System
|
- Name
- From Node
- To Node
- Contributes to HVDC (Yes/No)
- Resistance
- Reactance
- Capacity (Summer/Winter)
|
|
Branch Constraint
|
- A Transpower defined Constraint affecting a single Circuit (by imposing a limit on power transfer on the circuit)
|
- Name
- Circuit
- Start Date and Period
- End Date and Period
- Value
|
|
Equation Constraint
|
- A Transpower defined Constraint involving more than one circuit
|
- Name
- Start Date and Period
- End Date and Period
- Affected circuits
- Constraint Equation
- Limit (RHS)
|
|
Reserve Region
|
- A Transpower defined Region used for calculating
|
|
Market Entities
The following table lists and describes the Market entities modelled in EMarketOffer
| Entity |
Description |
Attribute (Trait)
|
|
Market Node
|
- A system Node at which electricity can be injected or withdrawn and for which a Nodal Price is published in the NZEM
|
|
|
Unit
|
- A single physical electricity generation Unit for which Offers can be made
|
- Name
- Connection (Market Node)
|
|
Generator
|
- A logical collection of (typically geographically co-located) Units
|
|
Commercial Entities
The following table lists and describes the Commercial entities modeled in EMarketOffer
| Entity |
Description |
Attribute (trait)
|
|
Company
|
- An owner of Generation capacity
|
- Name
- Unit(s)
- Unit Name
- Cost in dollars per MWh
- Retail Node(s)
- Node Name
- Percentage load owned
- Retail price in dollars per MWh
- Hedge Contract(s)
- Reference Node name
- Hedge start date
- Hedge start period
- Hedge end date
- Hedge end period
- Strike price in dollars per MWh
- Quantity (MW)
|
Geographical Items
The following table lists and describes the Geographical items modelled in EMarketOffer
| Item (entity) |
Description |
Attribute (trait)
|
|
Region
|
- A logical collection of Substations (typically but not necessarily geographically co-located)
|
- Name
- Component System nodes
|
Note: The Items listed above are not all modelled at the same level in EMarketOffer. For example no distinction is made in the program between System and Market Nodes with Prices being calculated for all System Nodes in Forecasts. Also Branch Constraints are treated as complex attributes of individual circuits rather than Items in their own right.
Dynamic Data
Dynamic data Traits that changes value frequently, typically by Trading Period. The following table lists the dynamic data items modelled in the EMarketOffer:
| Modelled Item |
Attribute |
Units |
Comment
|
| Circuit
|
- Capacity
|
- MW
|
- Can be re-rated by the Trading Period
|
- Powerflow
|
- MW
|
|
- Price Separation
|
- dollars per MWh
|
- Price difference on a constrained Circuit
|
- Losses
|
- MW
|
|
- Loading
|
- ratio
|
- Ratio of flow to capacity
|
| Company
|
- Generation
|
- MWh
|
- Across all Generators owned by the Company
|
- Generation Revenue
|
- dollars
|
|
- Generation Cost
|
- dollars
|
- Based on Generation marginal cost
|
- Retail Load
|
- MWh
|
- Across all Nodes supplied by the Generator
|
- Retail Revenue
|
- dollars
|
|
- Retail Cost
|
- dollars
|
- Nodal Price - Retail Price
|
- Hedge Cash Flow
|
- dollars
|
- (Nodal Price - Strike Price) * Quantity
|
- Total Cash Flow
|
- dollars
|
- The sum of all revenues and costs
|
| Equation Constraint
|
- Limit
|
- MWh
|
- Can be re-rated by the Trading Period
|
- Value
|
- MWh
|
|
- Freedom
|
- MWh
|
- Limit - Value
|
| Company
|
- Generation
|
- MWh
|
|
| Node
|
- Load
|
- MWh
|
|
- Generation
|
- MWh
|
|
- Price
|
- dollars per MWh
|
|
- Losses
|
- MWh
|
|
| Region
|
- Load
|
- MWh
|
- Across all Region Nodes
|
- Generation
|
- MWh
|
- Across all Region Nodes
|
- Price
|
- dollars per MWh
|
- Across all Region Nodes
|
- Losses
|
- MWh
|
- Across all Region Nodes
|
| Reserve Region
|
- Offered Fast Reserve
|
- MWh
|
- North and South Island
|
- Offered Sustained Reserve
|
- MWh
|
- North and South Island
|
- Cleared Fast Reserve
|
- MWh
|
- North and South Island
|
- Cleared Sustained Reserve
|
- MWh
|
- North and South Island
|
- Price Fast Reserve
|
- dollars per MWh
|
- North and South Island
|
- Price Sustained Reserve
|
- dollars per MWh
|
- North and South Island
|
- DC Offset Fast Reserve
|
- dollars per MWh
|
- North and South Island
|
- DC Offset Sustained Reserve
|
- dollars per MWh
|
- North and South Island
|
- AC Offset Fast Reserve
|
- dollars per MWh
|
- North and South Island
|
- AC Offset Sustained Reserve
|
- dollars per MWh
|
- North and South Island
|
- Base Risk Fast Reserve
|
- MW
|
- North and South Island
|
- Base Risk Sustained Reserve
|
- MW
|
- North and South Island
|
- Risk Adjustment Factor Fast Reserve
|
|
- North and South Island
|
- Risk Adjustment Factor Sustained Reserve
|
|
- North and South Island
|
| Substation
|
- Load
|
- MWh
|
- Averaged across all Nodes
|
- Generation
|
- MWh
|
- Averaged across all Units
|
- Price
|
- dollars per MWh
|
- Averaged across all Nodes
|
- Losses
|
- MW
|
- Averaged across all Nodes
|
| Unit
|
- Generation
|
- MW
|
|
- Fast Reserve dispatched
|
- MW
|
|
- Sustained Reserve dispatched
|
- MW
|
|
- Marginal Indicator
|
|
- Indicates if Unit was marginal for the Trading Period in question
|
- Risk Setter
|
|
- Indicates if Unit was setting the risk for the Trading Period in question
|
- Maximum Generation
|
- MW
|
- Maximum generation a unit is capable of producing in the Trading Period (used in Reserves calculation)
|
- Fast Reserve Offer Quatity (PLSR) bands 1-3
|
- MW
|
|
- Fast Reserve Offer Price (PLSR) bands 1-3
|
- dollars per MWh
|
|
- Fast Reserve RSlope (PLSR) bands 1-3
|
|
|
- Sustained Reserve Offer Quantity (PLSR) bands 1-3
|
- MW
|
|
- Sustained Reserve Offer Price (PLSR) bands 1-3
|
- dollars per MWh
|
|
- Sustained Reserve RSlope (PLSR) bands 1-3
|
|
|
- Fast Reserve Offer Quantity (TWD/ILR) bands 1-3
|
- MW
|
|
- Fast Reserve Offer Price (TWD/ILR) bands 1-3
|
- dollars per MWh
|
|
- Sustained Reserve Offer Quantity (TWD/ILR) bands 1-3
|
- MW
|
|
- Sustained Reserve Offer Price (TWD/ILR) bands 1-3
|
- dollars per MWh
|
|
- Frequency keeping band
|
- MW
|
|
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