One-way Transmission Link

Overview

One-way Transmission Link assets in Macro represent a unidirectional commodity transmission infrastructure that links a source node to a destination node. These assets are specified using JSON or CSV input files located in the assets directory, usually named with descriptive identifiers such as oneway_transmissions.json or oneway_transmissions.csv.

Asset Structure

A One-way Transmission Link asset consists of one main component:

Transmission Edge: Represents the unidirectional flow of a commodity from a start node to an end node with capacity constraints and losses

Here is a simple graphical representation of the One-way Transmission Link asset:

%%{init: {'theme': 'base', 'themeVariables': { 'background': '#D1EBDE' }}}%% flowchart LR subgraph OneWayTransmissionLink direction LR A((Commodity)) e1@-->|OneWayTransmission| B((Commodity)) e1@{ animate: true } end style A r:40,fill:#FFD700,stroke:black,color:black,stroke-dasharray: 3,5; style B r:40,fill:#FFD700,stroke:black,color:black,stroke-dasharray: 3,5; linkStyle 0 stroke:#FFD700, stroke-width: 2px;

Input File (Standard Format)

The easiest way to include a One-way Transmission Link asset in a model is to create a new file (either JSON or CSV) and place it in the assets directory together with the other assets.

your_case/
├── assets/
│   ├── oneway_transmissions.json    # or oneway_transmissions.csv
│   ├── other_assets.json
│   └── ...
├── system/
├── settings/
└── ...

This file can either be created manually, or using the template_asset function. The file will be automatically loaded when you run your Macro model.

The following is an example of a One-way Transmission Link asset input file:

{
    "link": [
        {
            "type": "OneWayTransmissionLink",
            "instance_data": [
                {
                    "id": "SE_to_MIDAT_oneway",
                    "commodity": "Electricity",
                    "transmission_origin": "elec_SE",
                    "transmission_dest": "elec_MIDAT",
                    "distance": 491.4512001,
                    "existing_capacity": 5552,
                    "max_capacity": 27760,
                    "investment_cost": 40219,
                    "loss_fraction": 0.04914512,
                    "transmission_constraints": {
                        "MaxCapacityConstraint": true
                    }
                }
            ]
        }
    ]
}

Global Data vs Instance Data

When working with JSON input files, the global_data field can be used to group data that is common to all instances of the same asset type. This is useful for setting constraints that are common to all instances of the same asset type and avoid repeating the same data for each instance.

Essential Attributes

Field	Type	Description
`type`	String	Asset type identifier: "OneWayTransmissionLink"
`id`	String	Unique identifier for the One-way Transmission Link instance
`commodity`	String	Commodity type being transmitted (e.g., "Electricity")
`transmission_origin`	String	Origin node identifier
`transmission_dest`	String	Destination node identifier

Constraints configuration

One-way Transmission Link assets can have different constraints applied to them, and the user can configure them using the following fields:

Field	Type	Description
`transmission_constraints`	Dict{String,Bool}	List of constraints applied to the transmission edge.

Users can refer to the Adding Asset Constraints to a System section of the User Guide for a list of all the constraints that can be applied to a transmission edge.

Default constraints

To simplify the input file and the asset configuration, the following constraints are applied to the One-way Transmission Link asset by default:

Capacity constraint (applied to the transmission edge)

Investment Parameters

Field	Type	Description	Units	Default
`can_retire`	Boolean	Whether capacity can be retired	-	false
`can_expand`	Boolean	Whether capacity can be expanded	-	true
`existing_capacity`	Float64	Initial installed capacity	MW	0.0
`capacity_size`	Float64	Unit size for capacity decisions	-	1.0

Additional Investment Parameters

Maximum and minimum capacity constraints

If MaxCapacityConstraint or MinCapacityConstraint are added to the constraints dictionary for the transmission edge, the following parameters are used by Macro:

Field	Type	Description	Units	Default
`max_capacity`	Float64	Maximum allowed capacity	MW	Inf
`min_capacity`	Float64	Minimum allowed capacity	MW	0.0

Economic Parameters

Field	Type	Description	Units	Default
`investment_cost`	Float64	CAPEX per unit capacity	/MW	0.0
`annualized_investment_cost`	Union{Nothing,Float64}	Annualized CAPEX	/MW/yr	calculated
`fixed_om_cost`	Float64	Fixed O&M costs	/MW/yr	0.0
`variable_om_cost`	Float64	Variable O&M costs	/MWh	0.0
`wacc`	Float64	Weighted average cost of capital	fraction	0.0
`lifetime`	Int	Asset lifetime in years	years	1
`capital_recovery_period`	Int	Investment recovery period	years	1
`retirement_period`	Int	Retirement period	years	0

Operational Parameters

Field	Type	Description	Units	Default
`distance`	Float64	Distance between nodes	km	0.0
`loss_fraction`	Float64	Fraction of power lost during transmission	fraction	0.0
`unidirectional`	Boolean	Whether the transmission is unidirectional	-	true

Types - Asset Structure

The OneWayTransmissionLink asset is defined as follows:

struct OneWayTransmissionLink{T} <: AbstractAsset
    id::AssetId
    transmission_edge::UnidirectionalEdge{<:T}
end

Constructors

Default constructor

OneWayTransmissionLink(id::AssetId, transmission_edge::UnidirectionalEdge{<:T})

Factory constructor

make(asset_type::Type{OneWayTransmissionLink}, data::AbstractDict{Symbol,Any}, system::System)

Field	Type	Description
`asset_type`	`Type{OneWayTransmissionLink}`	Macro type of the asset
`data`	`AbstractDict{Symbol,Any}`	Dictionary containing the input data for the asset
`system`	`System`	System to which the asset belongs

Examples

This section contains examples of how to use the One-way Transmission Link asset in a Macro model.

Single one-way transmission link between zones

JSON Format:

{
    "link": [
        {
            "type": "OneWayTransmissionLink",
            "global_data": {
                "transmission_constraints": {
                    "MaxCapacityConstraint": true
                }
            },
            "instance_data": [
                {
                    "id": "SE_to_MIDAT_oneway",
                    "commodity": "Electricity",
                    "transmission_origin": "elec_SE",
                    "transmission_dest": "elec_MIDAT",
                    "distance": 491.4512001,
                    "existing_capacity": 5552,
                    "max_capacity": 27760,
                    "investment_cost": 40219,
                    "loss_fraction": 0.04914512
                }
            ]
        }
    ]
}

CSV Format:

Type	id	commodity	transmission_origin	transmission_dest	distance	existing_capacity	max_capacity	investment_cost	loss_fraction	transmission_constraints–MaxCapacityConstraint
OneWayTransmissionLink	SE_to_MIDAT_oneway	Electricity	elec_SE	elec_MIDAT	491.4512001	5552	27760	40219	0.04914512	true

Best Practices

Prefer global_data for shared fields and constraints across instances.
Ensure loss_fraction reflects realistic transmission losses for the distance and technology used.
Use descriptive IDs that indicate origin and destination.
Validate capacity-related cost and technology parameters before large-scale runs.

Input File (Advanced Format)

The advanced format mirrors the asset's hierarchical structure. A One-way Transmission Link asset is composed of a single transmission edge, represented by a UnidirectionalEdge object. The input file is therefore organized as follows:

{
    "edges": {
        "transmission_edge": {
            // ... transmission_edge-specific attributes ...
        }
    }
}

Below is an example of an input file using the advanced format for a One-way Transmission Link asset.

{
    "link": [
        {
            "type": "OneWayTransmissionLink",
            "global_data": {
                "edges": {
                    "transmission_edge": {
                        "commodity": "Electricity",
                        "has_capacity": true,
                        "unidirectional": true,
                        "can_expand": true,
                        "can_retire": false,
                        "integer_decisions": false,
                        "constraints": {
                            "CapacityConstraint": true,
                            "MaxCapacityConstraint": true
                        }
                    }
                }
            },
            "instance_data": [
                {
                    "id": "SE_to_MIDAT_oneway",
                    "edges": {
                        "transmission_edge": {
                            "start_vertex": "elec_SE",
                            "end_vertex": "elec_MIDAT",
                            "distance": 491.4512001,
                            "existing_capacity": 5552,
                            "max_capacity": 27760,
                            "investment_cost": 40219,
                            "loss_fraction": 0.04914512
                        }
                    }
                }
            ]
        }
    ]
}

Key Points

The global_data field is utilized to define attributes and constraints that apply universally to all instances of a particular asset type.
The start_vertex and end_vertex fields indicate the nodes to which the transmission edge is connected. These nodes must be defined in the nodes.json file.
For a comprehensive list of attributes that can be configured for the edge component, refer to the edges page of the Macro manual.