The Power Generating Module Document — PGMD is the document a generation customer uses to demonstrate to the DNO that their Power Generating Module meets the requirements of G99. It sits at the heart of the compliance evidence for larger projects, and it's tightly linked to the operational notifications a project needs to receive.
When is a PGMD required?
A PGMD is required for all Type B, C and D Power Generating Modules. In UK terms:
- Type B: 1MW to under 10MW.
- Type C: 10MW to under 50MW.
- Type D: 50MW or more, or connected above 110kV.
Projects below 1MW (Type A) don't need a PGMD — they're covered by the standard G99 forms alone.
What goes into it?
A PGMD brings together the technical evidence that shows the generating module will behave as required on the network. That includes:
- Manufacturer information and type-test references for the generating units.
- Simulation studies where required.
- Protection settings and interface protection details.
- Operational parameters — how the plant responds to voltage and frequency events, reactive power capability, and so on.
- Any site-specific compliance evidence needed because equipment isn't fully type-tested.
It isn't a single one-page form; it's a structured document that's built up over the course of the connection process.
When do you submit it?
The PGMD is completed and updated in stages. Two milestones matter:
- Shortly after accepting the connection offer, a first draft is ideally submitted. This gives the DNO early visibility of the compliance approach and flags any gaps while there's still time to close them.
- At least 28 days before synchronising, the PGMD must be with the DNO. This is the minimum notice period — leaving it later than that will delay first sync.
Why the PGMD matters for your FON
A project doesn't have permanent rights to generate until it has received its Final Operational Notification (FON) from the DNO (see our article on EONs, IONs, LONs and FONs).
To get the FON, you must submit a final version of the PGMD with correct data — meaning any information that was previously estimated or left blank has to be filled in with the real, measured, commissioned values. A PGMD full of "TBC" won't unlock a FON, and without a FON the plant can only run under interim or limited arrangements.
Practical implications for developers
- Start early. Treat the PGMD as a live document from connection-offer acceptance onwards, not a commissioning-stage deliverable.
- Keep manufacturer evidence traceable. Type-test references, inverter datasheets and protection relay information all need to line up with what's in the PGMD.
- Update it after each design change. Inverter substitutions, protection re-settings and layout changes all affect the PGMD content and can invalidate an earlier draft.
- Plan the 28-day window backwards. If you have a target first-sync date, the finalised PGMD needs to be in the DNO's hands at least four weeks earlier — and realistically longer to allow for their review.
Do smaller projects need something similar?
No. For Type A projects (under 1MW), the standard G99 evidence forms — A2-1, A2-2, A2-3, A2-4 depending on the technology and whether interface protection is type-tested — cover the same ground in a much lighter format. The PGMD is specifically the mechanism for Type B and above, because those projects need more detailed engineering evidence to protect the network.
If your project sits at the edge of the 1MW threshold, it's worth confirming its classification early — the difference in documentation load either side of that line is significant.