gb-full
is the national network as a case file the solver actually runs: every distribution licence area in
Britain plus the transmission spine, distilled from 38,109 real network nodes, geolocated bus by bus,
and shipped already converged. Load it, and you are holding the country at a residual of
3.6×10−11 pu. This page is the datasheet.
The DNOs publish their networks the way accountants publish ledgers — exhaustively, and in a form you cannot solve. Long-term development statements model every busbar section, every zero-impedance jumper, every star point as its own node. The pipeline's job is to collapse the bookkeeping without touching the electricity.
38,109 nodesEvery node the DNO and NESO publications describe, taken in whole from the lake — long-term development statements, asset registers, the TEC register, GSP geography. No sampling, no "representative subset". The full ledger, exactly as Britain filed it.
→ 4,240 busesNodes joined by zero-impedance links are the same electrical point wearing different name badges. The collapse merges 2,910 busbar ties and dissolves 10 star nodes — pure bookkeeping removed, admittance matrix untouched in meaning.
→ 3,539 busesThe subtle one. UKPN's three areas (EPN, LPN, SPN) and SP Manweb publish busbar sections as separate nodes without the couplers that join them — so a single substation arrives as two or three disconnected fragments. The merge rejoins 702 split section nodes, gated on matching name and matching voltage, so two distinct substations can never be combined by accident.
machine εAfter every reduction stage the model is re-solved and re-checked by the independent residual instrument. The reduced model re-validates to the same machine-epsilon residual — the merge is electrically faithful, and I can prove it rather than assert it.
The point of the exercise is not a smaller number. It is a model where every bus is a real electrical node with a real name, a real voltage and a real place on the map — and nothing else.
A network model is a list of promises. Here is the full set, so you can audit mine before you rely on them.
| Quantity | Value | Notes |
|---|---|---|
| Branches | ||
| Branches, total | 5,918 | every one carrying an impedance and a rating |
| — series branches | 2,719 | lines and cables |
| — transformers | 1,413 | modelled with ratio and impedance |
| — of which OLTCs | 1,383 | on-load tap changers under live tap control in the solve loop, not frozen at nominal |
| Demand | ||
| Demand carried | 48,870 MW | real LTDS demand, not a uniform smear |
| Load points | 1,141 | each attached where the DNO says the load lives |
| Generation | ||
| Embedded generation, capacity | 127,616 MW | from the embedded capacity registers |
| Embedded generation, dispatched | 49,867 MW | the operating point actually solved |
| Transmission generation (TEC-attached) | 92,997 MW | 572 units, placed from the TEC register |
| Topology & reference | ||
| Islands | 2 | largest island 3,536 buses |
| Slack bus | bus 194 — Melksham | the spine node with the largest incident branch rating: 21,000 MVA. Chosen by the network, not by taste. |
| Voltage filter | ≥132 kV | lower voltages appear only as attachment points |
The model is filtered to 132 kV and above as a network; the sub-132 kV buses that remain are attachment points — the places where demand and embedded generation reach up and grab the grid.
| Nominal voltage | Buses | Role |
|---|---|---|
| 400 kV | 113 | the supergrid — the country's spine |
| 275 kV | 203 | transmission, the older half of the spine |
| 132 kV | 2,281 | the distribution backbone — where most of Britain actually hangs |
| 66 kV | 54 | attachment points |
| 33 kV | 843 | attachment points |
| 25 kV | 34 | attachment points (railway supplies, mostly) |
| 22 kV | 11 | attachment points |
| Total | 3,539 |
Note where the mass is: 2,281 of the 3,539 buses sit at 132 kV. Great Britain is not 400 kV with some detail bolted on — it is a distribution country with a transmission spine, and the model respects that ratio.
Most GB studies stop at the transmission spine and hand-wave the rest. This model was assembled the long way — from NGED, UKPN, Northern Powergrid, SSEN, SPEN, ENW and NGET published data, area by area, with each area's buses counted, named and placed.
| Area | Operator | Buses |
|---|---|---|
| EMID | NGED — East Midlands | 432 |
| ENWL | Electricity North West | 168 |
| EPN | UKPN — Eastern | 321 |
| LPN | UKPN — London | 126 |
| NGET | National Grid — the transmission spine | 316 |
| NPGN | Northern Powergrid — Northeast | 166 |
| NPGY | Northern Powergrid — Yorkshire | 372 |
| SEPD | SSEN — Southern | 369 |
| SPM | SP Energy Networks — Manweb | 224 |
| SPN | UKPN — South Eastern | 185 |
| SWALES | NGED — South Wales | 336 |
| SWEST | NGED — South West | 227 |
| WMID | NGED — West Midlands | 297 |
| TOTAL | 14/14 licence areas represented | 3,539 |
The two Scottish licence areas are carried on the spine: their demand and generation attach at NGET GSP buses rather than as separately-modelled distribution networks — see the full disclosure below.
Thirteen distribution and transmission networks, seven publishing organisations, one coherent admittance matrix. If your study touches a GSP, a DNO boundary or an embedded fleet, the network it lives on is already in the file.
A bus without coordinates is a spreadsheet row. A bus with coordinates is a substation. Geolocation was done the honest way — direct matching first, GSP-region hinting second, and the stragglers run to ground rather than quietly deleted.
The model is not just solvable, it is drawable. Three ready-made layers drop straight onto any web map or GIS tool, in plain GeoJSON with no proprietary wrapper.
| Layer | Size | Contents |
|---|---|---|
| assets.geojson | 5.2 MB | every bus and branch, placed |
| dno_areas.geojson | 1.3 MB | the fourteen licence-area polygons |
| gsp_regions.geojson | 7.6 MB | Grid Supply Point region boundaries |
The ETYS boundary corridors are modelled with their real MW limits — not decorative lines on a map, but constraints the solver can bind against. Run a constraint study and it runs against the same boundaries the control room watches.
Each corridor carries its published transfer limit, so a boundary-flow question gets a number with a constraint attached — and a verdict when the constraint binds.
Most tools hand you a topology and wish you luck with initialisation. gb-full ships with a converged operating point baked in — solved at 0.70 × LTDS maximum demand, taps set, voltages banded, losses accounted. Your first solve is a warm start on a national grid.
Three Newton iterations on the final pass is what a well-conditioned national model looks like. Eight OLTC passes means the tap-control loop genuinely hunted — 953 of 1,383 taps ended off-nominal, which is the model doing the voltage regulation the real network does, rather than pinning everything at 1.0 pu and calling it a day. And the voltage band sits comfortably inside statutory limits without a single cosmetic clamp.
Behind the solved case sits the full asset graph it was distilled from — 734,913 assets and 1,016,912 edges — so every bus can be traced back through the reduction to the published records that put it there.
case: gb-full operating_point: 0.70 × LTDS maximum demand newton_iterations: 3 # final pass oltc_passes: 8 # 1,383 controlled taps max_mismatch_pu: 3.6e-11 voltage_band_pu: [0.9802, 1.0457] losses_mw: 267 taps_off_nominal: 953 slack: bus 194 "Melksham" (21,000 MVA) asset_graph: 734,913 assets / 1,016,912 edges status: CONVERGED — ships in this state
NGET does not publish circuit-by-circuit connectivity. Nobody outside the control room has the real wiring diagram, and any vendor implying otherwise is selling you a guess without the label. My guess wears the label: the spine topology is a Delaunay/Gabriel geometric reconstruction over the real GSP sites — triangulate the actual substation locations, keep the edges physics and geography would keep, dress them with real ratings.
Everything the spine connects is real: real buses, real demand, real generation, real transformers, all from published DNO and NESO data. The reconstruction is the wiring between them, nothing more. And it has artefacts I will name rather than bury — the Alverdiscott–Pembroke corridor spans 96 km over the Bristol Channel, a line no sane planner would build, kept because the reconstruction needs it for connectivity. Scottish demand and generation attach at GSP spine buses rather than through separately-modelled Scottish distribution networks.
None of this moves the physics: the model re-validates to machine epsilon either way. But you deserved to know before you licensed it, not after.
This is the only asterisk on the page. Everything above it — the bus counts, the demand, the taps, the residual — is exactly as stated.
gb-full ships with GridSim Core; the GDA data lake keeps it pinned to the public record, settlement period by settlement period.