Network Data#

Detailed documentation of the transmission network data.

ETYS Network Structure#

The full ETYS network represents the GB transmission system at high resolution.

Buses (Substations)#

Each bus represents a substation in the transmission network.

Key attributes:

Attribute

Description

Example

name

Unique identifier

BEAU41

v_nom

Nominal voltage (kV)

400, 275, 132

x

Easting (OSGB36, m)

267000

y

Northing (OSGB36, m)

843000

carrier

Bus type

AC

zone

DNO region

SSE-N

Naming convention:

  • First 4 characters: Location code

  • Last 2 characters: Voltage code

    • 41 = 400kV

    • 21 = 275kV

    • 11 = 132kV

Example: BEAU41 = Beauly substation, 400kV

Lines (Circuits)#

Transmission lines connecting substations.

Key attributes:

Attribute

Description

Units

bus0

From bus

-

bus1

To bus

-

s_nom

Thermal rating

MVA

r

Resistance

p.u.

x

Reactance

p.u.

b

Susceptance

p.u.

length

Circuit length

km

num_parallel

Parallel circuits

-

Transformers#

Connections between voltage levels.

Key attributes:

Attribute

Description

Units

bus0

High voltage bus

-

bus1

Low voltage bus

-

s_nom

Rating

MVA

x

Reactance

p.u.

tap_ratio

Tap position

-

Voltage Levels#

The GB transmission network has three main voltage levels:

Voltage

Usage

Operator

400kV

Supergrid backbone

NESO/TO

275kV

Regional transmission

NESO/TO

132kV

Sub-transmission (Scotland)

SHE-T, SPT

Note

In England and Wales, 132kV is distribution (DNO-operated). In Scotland, 132kV is transmission (TO-operated).

Transmission Owners#

Operator

Region

Key Corridors

SHE Transmission

North Scotland

Beauly-Denny

SP Transmission

Central Scotland

Hunterston-Torness

NGET

England & Wales

North-South flows

OFTO

Offshore

Wind farm connections

Key Transmission Boundaries#

Critical network boundaries that often constrain flows:

B6 Boundary (Scotland-England)#

The major constraint between Scotland and England.

Circuits:

  • Harker-Strathaven (400kV)

  • Eccles-Stella West (400kV)

  • HVDC (Western Link, Eastern Link)

Typical capacity: 6-8 GW (depends on year)

B4 Boundary (Central Scotland)#

        flowchart TB
    NORTH["North Scotland"] 
    CENTRAL["Central Belt"]
    ENGLAND["England"]
    
    NORTH -->|"B4"| CENTRAL
    CENTRAL -->|"B6"| ENGLAND

Network Files#

Location#

data/network/
├── ETYS/
│   ├── ETYS 2024 Appendix-B V1.xlsx    # ETYS 2024 circuits, transformers, HVDC
│   ├── ETYS Appendix B 2023.xlsx        # ETYS 2023 (alternative)
│   ├── ETYS Appendix B 2022.xlsx        # ETYS 2022 (alternative)
│   ├── GB_network.xlsx                  # Extra WF edges, BMU mappings, demand nodes
│   ├── substation_coordinates.csv       # Manually compiled bus coordinates
│   ├── Regional breakdown of FES24 data.xlsx  # FES regional capacity by GSP
│   └── ...                              # FES regional files for other years
├── reduced_network/
│   ├── buses.csv
│   └── lines.csv
└── zonal/
    ├── buses.csv
    └── links.csv

The ETYS publication year is selected via the etys.year configuration option (see Configuration Reference). The etys_file_registry.py module maps each publication year (2022, 2023, 2024) to the correct filenames and Excel sheet names.

Loading Network Data#

import pypsa

# Load a built network
n = pypsa.Network("resources/network/HT35_network.nc")

# Inspect buses
print(n.buses.head())

# Inspect lines
print(n.lines.head())

# Inspect transformers
print(n.transformers.head())

Network Upgrades#

ETYS includes planned reinforcements through 2031+ (depending on ETYS publication year).

Applying Upgrades#

# In scenario configuration
etys_upgrades:
  enabled: true
  upgrade_year: 2035  # Apply all upgrades through 2035 (null = use modelled_year)

Upgrades are read from the ETYS Appendix B Excel file selected by etys.year. The upgrade sheets are organized by transmission owner:

Sheet

Content

B-2-2a

Circuit changes (SHE Transmission)

B-2-2b

Circuit changes (SP Transmission)

B-2-2c

Circuit changes (NGET)

B-2-2d

Circuit changes (OFTO)

B-3-2a

Transformer changes (SHE Transmission)

B-3-2b

Transformer changes (SP Transmission)

B-3-2c

Transformer changes (NGET)

B-3-2d

Transformer changes (OFTO)

Types of Upgrades#

  • Circuit additions: New transmission lines

  • Circuit removals: Decommissioned lines

  • Circuit modifications: Uprating existing circuits

  • Transformer additions: New transformers between voltage levels

  • Transformer removals: Decommissioned transformers

  • Transformer modifications: Re-rated transformers

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

Bus Placement for Upgrades#

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

  1. Strategy 0: Lookup in substation_coordinates.csv (WGS84 → OSGB36 conversion)

  2. Strategy 1: Copy coordinates from a same-site bus already in the network

  3. Strategy 2: Copy from a bus added earlier in the same upgrade batch

  4. Strategy 3: Estimate from a connected bus using circuit length as offset

After applying upgrades, orphan buses (disconnected from the network) are automatically removed.

Coordinate System#

OSGB36 (British National Grid)#

The network uses OSGB36 coordinates:

  • EPSG: 27700

  • Units: Meters

  • Origin: Southwest of Cornwall

Dimension

Range

X (Easting)

0 - 700,000

Y (Northing)

0 - 1,200,000

Converting to WGS84#

from pyproj import Transformer

# Create transformer
transformer = Transformer.from_crs(
    "EPSG:27700",  # OSGB36
    "EPSG:4326",   # WGS84
    always_xy=True
)

# Convert (x, y) to (lon, lat)
lon, lat = transformer.transform(267000, 843000)
print(f"Beauly: {lat:.4f}°N, {lon:.4f}°W")

Visualizing the Network#

Basic Plot#

import pypsa
import matplotlib.pyplot as plt

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

fig, ax = plt.subplots(figsize=(8, 10))
n.plot(ax=ax, line_widths=0.5)
plt.title("GB Transmission Network")
plt.tight_layout()
plt.savefig("gb_network.png", dpi=150)

With Generation#

# Size buses by generation capacity
bus_gen = n.generators.groupby('bus').p_nom.sum()

n.plot(
    bus_sizes=bus_gen / 500,  # Scale factor
    bus_colors=bus_gen,
    line_widths=1,
    line_colors='gray'
)

Interactive Map#

import folium
from pyproj import Transformer

# Convert coordinates and create map
transformer = Transformer.from_crs("EPSG:27700", "EPSG:4326", always_xy=True)

m = folium.Map(location=[54.5, -2], zoom_start=6)

for idx, bus in n.buses.iterrows():
    lon, lat = transformer.transform(bus.x, bus.y)
    folium.CircleMarker(
        [lat, lon],
        radius=3,
        popup=idx
    ).add_to(m)

m.save("network_map.html")

Data Quality#

Validation Checks#

The workflow validates network data:

  1. Connectivity: All buses reachable

  2. Parameters: R, X, B in reasonable ranges

  3. Coordinates: All buses have valid locations

  4. Ratings: All lines have positive s_nom

Known Issues#

Issue

Description

Handling

Missing coordinates

Some ETYS buses lack x,y

Multi-tier resolution: GSP mapping → substation lookup → prefix fallback → distance-weighted guessing with land boundary validation

Zero impedance

Some short lines

Minimum impedance applied

Islanded buses

Disconnected substations

Connected via small impedance

Offshore buses

Wind farm connection buses outside GB landmass

Identified via OFTO data; is_offshore flag propagated through the pipeline

Land boundary

Guessed coordinates may fall in the sea

Coordinates validated against GSP region GeoJSON boundaries and moved to nearest land point