Network Models#

PyPSA-GB supports three network models with different levels of detail.

Overview#

Model

Buses

Lines

Transformers

Typical Solve Time

ETYS

~2000

~3000

~500

30-60 min/week

Reduced

32

64

10

2-5 min/week

Zonal

17

~30

-

1-2 min/week

ETYS Network#

The full Electricity Ten Year Statement network from National Grid ESO.

network_model: "ETYS"

Characteristics#

  • Complete 400kV and 275kV transmission network

  • All substations and switching points

  • Detailed transformer ratings

  • Planned reinforcements available

  • Multi-year support: Select ETYS publication year (2022, 2023, or 2024) via etys.year

Two-Stage Build Pipeline#

The ETYS network is built in two stages:

  1. Data extraction (process_ETYS_data): Parses the raw ETYS Appendix B Excel file into intermediate CSVs for circuits, transformers, HVDC, and buses. Also processes offshore wind farm connections from GB_network.xlsx.

  2. Network assembly (build_ETYS_base_network): Assembles the CSVs into a PyPSA network with coordinate resolution, land boundary validation, and optional upgrade application.

Coordinate Resolution#

Many ETYS buses lack explicit coordinates. A multi-tier strategy resolves missing locations:

  1. GSP mapping: Explicit node-to-GSP mapping from the Dem_per_node sheet of GB_network.xlsx

  2. Substation coordinates: Lookup from substation_coordinates.csv (WGS84 → OSGB36 conversion)

  3. Prefix fallback: Match the 4-character location prefix to other buses at the same site

  4. Distance-weighted guessing: Iterative estimation from connected buses using circuit lengths

All guessed coordinates are validated against GB land boundaries (GSP region GeoJSON). Points that fall in the sea are moved to the nearest land point.

Offshore Bus Identification#

Buses serving offshore wind farm connections are identified via OFTO data and flagged with is_offshore = True. These are excluded from land boundary validation.

Use Cases#

  • Production analysis requiring accurate constraints

  • Locational marginal pricing studies

  • Network constraint analysis

  • Investment planning

Data Source#

Based on ETYS Appendix B data (selected via etys.year), including:

  • Circuit parameters (R, X, B, rating) from sheets B-2-1a/b/c/d (SHE-T/SPT/NGET/OFTO)

  • Transformer impedances and tap positions from sheets B-3-1a/b/c/d

  • HVDC data from sheet B-5-1

  • Bus coordinates from substation data and supplementary sources

  • Planned upgrades timeline from sheets B-2-2a/b/c/d and B-3-2a/b/c/d

Reduced Network#

A 32-bus equivalent capturing major flow paths.

network_model: "Reduced"

Topology#

        flowchart TB
    subgraph Scotland
        SHETL["SHETL Zone"]
        SPTL["SPTL Zone"]
    end
    
    subgraph England
        NORTH["North"]
        MIDLANDS["Midlands"]
        LONDON["London"]
        SOUTH["South"]
    end
    
    subgraph Wales
        WALES["Wales"]
    end
    
    SHETL --> SPTL
    SPTL --> NORTH
    NORTH --> MIDLANDS
    MIDLANDS --> LONDON
    MIDLANDS --> WALES
    LONDON --> SOUTH
    WALES --> SOUTH

Use Cases#

  • Fast scenario testing

  • Sensitivity analysis

  • Educational purposes

  • Debugging workflow issues

Advantages#

  • 10-20x faster than ETYS

  • Still captures major constraints (Scotland-England, etc.)

  • Good enough for many policy questions

Limitations#

  • Loses locational detail within zones

  • Some constraint interactions missed

  • Not suitable for detailed LMP analysis

Zonal Network#

Maximum aggregation to 17 zones.

network_model: "Zonal"

Zones#

Aligned with DNO regions:

  • SSE-N (North Scotland)

  • SSE-S (South Scotland)

  • SPEN (SP Networks)

  • NPG-NE (Northern Powergrid NE)

  • NPG-Y (Northern Powergrid Yorkshire)

  • ENWL (Electricity North West)

  • WPD-EM (East Midlands)

  • WPD-WM (West Midlands)

  • WPD-SW (South West)

  • WPD-W (Wales)

  • UKPN-E (Eastern)

  • UKPN-L (London)

  • UKPN-SE (South East)

  • SSEN-S (Southern)

  • Northern Ireland (interconnected)

Use Cases#

  • Quick screening studies

  • Regional capacity analysis

  • Very fast iteration

Choosing a Network Model#

        flowchart TD
    Q1{Need locational\ndetail?}
    Q1 -->|Yes| Q2{Production\nrun?}
    Q1 -->|No| ZONAL[Zonal]
    
    Q2 -->|Yes| ETYS[ETYS]
    Q2 -->|No| Q3{Time\nconstrained?}
    
    Q3 -->|Yes| REDUCED[Reduced]
    Q3 -->|No| ETYS

Decision Guide#

Your Need

Recommended Model

Publication-quality results

ETYS

Constraint analysis

ETYS

Quick testing

Reduced

Parameter sweeps

Reduced

Regional aggregates

Zonal

Educational

Reduced or Zonal

Network Clustering#

For intermediate detail, cluster the ETYS network:

HT35_clustered:
  network_model: "ETYS"
  clustering:
    enabled: true
    n_clusters: 100

This reduces ETYS to ~100 buses while preserving:

  • Major transmission corridors

  • Generation locations (approximately)

  • Regional balance

See Network Clustering for details.

Coordinate Systems#

ETYS Network#

Uses OSGB36 (British National Grid):

  • X: Easting in meters (0-700,000)

  • Y: Northing in meters (0-1,200,000)

Conversion#

If you need WGS84 (lat/lon):

from pyproj import Transformer

# OSGB36 to WGS84
transformer = Transformer.from_crs("EPSG:27700", "EPSG:4326", always_xy=True)
lon, lat = transformer.transform(x_osgb, y_osgb)

ETYS Network Upgrades#

For future years, ETYS planned upgrades can be applied:

HT35_with_upgrades:
  modelled_year: 2035
  network_model: "ETYS"
  etys_upgrades:
    enabled: true
    upgrade_year: null   # null = use modelled_year

Upgrades are read from the same ETYS Appendix B file selected by etys.year. All upgrades with a commissioning year up to upgrade_year (or modelled_year if null) are applied.

Supported Upgrade Types#

  • Circuit additions: New transmission lines (with auto bus placement)

  • Circuit removals: Decommissioned lines

  • Circuit modifications: Uprated or re-routed circuits

  • Transformer additions: New inter-voltage transformers

  • Transformer removals: Decommissioned transformers

  • Transformer modifications: Re-rated transformers

  • HVDC additions: New DC links (e.g., Eastern HVDC)

New Bus Placement#

When upgrades reference buses not in the base network, coordinates are resolved via a multi-pass strategy:

Strategy

Method

0

Explicit lookup in substation_coordinates.csv (WGS84 → OSGB36)

1

Copy coordinates from a same-site bus already in the network

2

Copy from a bus added earlier in the same upgrade batch

3

Estimate from a connected bus using circuit length as directional offset

After applying all upgrades, remove_orphan_buses() cleans up any buses that became disconnected.

See the ETYS Appendix B documentation for the full upgrade timeline.

Visualizing Networks#

Load and plot any network:

import pypsa
import matplotlib.pyplot as plt

n = pypsa.Network("resources/network/HT35_network.nc")

fig, ax = plt.subplots(figsize=(10, 12))
n.plot(
    ax=ax,
    bus_sizes=n.generators.groupby('bus').p_nom.sum() / 1000,
    line_widths=1,
    title="ETYS Network - Generation Capacity"
)
plt.tight_layout()
plt.savefig("network_map.png", dpi=150)

Performance Comparison#

Benchmarks for a typical 1-week solve:

Model

Build Time

Solve Time

Memory

ETYS

5 min

45 min

8 GB

Reduced

1 min

3 min

2 GB

Zonal

30 sec

1 min

1 GB

Times vary based on hardware and solver.