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Transmission Settings

These parameters define inter-regional transmission network expansion costs, line losses, and reference data tables containing network topology.

Network Topology from Data Tables

Unlike generators and demand, transmission network structure (which regions connect, capacities, distances) is not defined in settings YAML. Instead, PowerGenome loads this from data tables configured via transmission_constraints_table and transmission_cost_table.

Data Table References

transmission_constraints_table

Type: String or dictionary Required: For database-based transmission data Example: "trancap_init_energy_wecc_pg.csv"

Table containing transmission capacity between base regions.

Simple:

transmission_constraints_table: transmission_capacity.csv

Advanced:

transmission_constraints_table:
  table_name: transmission.parquet
  scenario: high_capacity
  filters:
    - - [year, '=', 2030]

Expected columns:

  • region_from: Origin base region
  • region_to: Destination base region
  • firm_ttc_mw: Firm transmission capacity (MW)
  • nonfirm_ttc_mw: Non-firm capacity (optional)

PowerGenome aggregates these constraints across base regions according to region_aggregations.

transmission_cost_table

Type: String or dictionary Required: For pre-calculated transmission costs Example: "transmission_distance_cost_500kVac_annuity.csv"

Table with transmission line costs and losses calculated from least-cost-path analysis.

transmission_cost_table: network_costs.csv

Expected columns:

  • start_region: Origin model region
  • dest_region: Destination model region
  • total_interconnect_annuity_mw: Annualized cost ($/MW-yr)
  • total_interconnect_cost_mw: Total capital cost ($/MW)
  • total_line_loss_frac: Line loss as fraction (0.05 = 5%)
  • dollar_year: Cost basis year

user_transmission_costs

Type: String (filename in input_folder) Required: For user-specified transmission costs Example: "network_costs_wecc_6_zone.csv"

CSV file with transmission costs between model regions. Overrides database values.

user_transmission_costs: network_costs.csv

File format (extra_inputs/network_costs.csv):

start_region,dest_region,total_interconnect_annuity_mw,total_interconnect_cost_mw,total_line_loss_frac,dollar_year
northeast,midwest,15000,350000,0.08,2018
midwest,south,12000,280000,0.05,2018

Use Pre-Calculated Costs

PowerGenome can calculate costs from region centroids, but pre-calculated costs from least-cost-path analysis are strongly recommended. See Gagnon et al. (2023) for methodology.

Capacity Selection

tx_value_col

Type: String Required: No Default: "firm_ttc_mw" Options: "firm_ttc_mw" or "nonfirm_ttc_mw"

Which capacity column to use from transmission data tables.

tx_value_col: firm_ttc_mw

Firm vs non-firm:

  • Firm: Guaranteed capacity (lower value, more conservative)
  • Non-firm: Opportunistic capacity (higher value, less reliable)

PowerGenome v0.8+ defaults to firm_ttc_mw. Previous versions used nonfirm_ttc_mw.

distribution_loss_factor

Type: Float Required: For distributed generation Default: 0.0 Example: 0.06

Distribution-level line loss (transmission substation to customer).

distribution_loss_factor: 0.06  # 6% distribution loss

Used when subtracting distributed generation from total demand. Total demand includes distribution losses, so DG must be adjusted.

Expansion Controls

tx_expansion_per_period

Type: Float Required: For transmission expansion Example: 1.0

Maximum fractional expansion of existing transmission per planning period.

tx_expansion_per_period: 1.0  # Can double existing capacity

Interpretation:

  • 1.0: Can add 100% of existing capacity (500 MW → 1000 MW max)
  • 0.5: Can add 50% of existing (500 MW → 750 MW max)
  • 2.0: Can triple existing capacity

Combined with tx_expansion_mw_per_period — larger value governs each line.

tx_expansion_mw_per_period

Type: Integer Required: No Example: 500

Absolute expansion limit per line per period (MW).

tx_expansion_mw_per_period: 500  # Can add up to 500 MW

Useful for setting minimum buildable increments (e.g., one 230kV line ≈ 200-400 MW).

Expansion calculation per line:

max_expansion = max(
    existing_capacity * tx_expansion_per_period,
    tx_expansion_mw_per_period
)

GenX Output Files

PowerGenome generates these GenX transmission files:

Network.csv:

  • Network_Lines: Line ID number
  • z1, z2, ...: Network topology matrix
  • Line_Max_Flow_MW: Existing capacity
  • Line_Min_Flow_MW: Reverse flow limit (typically negative of max)
  • transmission_path_name: Human-readable name
  • Line_Loss_Percentage: Loss fraction
  • Line_Reinforcement_Cost_per_MWyr: Annualized expansion cost

GenX uses these files to optimize transmission expansion and inter-regional power flows.