G99 Protection Panels
Mains-protection relay panels for DNO compliance — built, tested and ready for witness testing.
Connecting generation to the network — solar, battery storage, CHP or standby plant running in parallel — means satisfying your DNO under Engineering Recommendation G99. ENICO builds the protection panel that gets you there: a protection relay configured to the settings in your connection agreement, wired to a shunt-trip device that disconnects your generation when the network needs it to.
We build standard G99 panels for the repeatable jobs and bespoke panels for the big ones — including systems up to 10 MW and distributed, multi-generator schemes — and we support commissioning so the DNO witness test goes smoothly the first time.
What's included
Protection relay configured to your connection agreement
Loss-of-mains, over/under voltage and over/under frequency protection set to the values your DNO has specified, recorded on a settings sheet in the documentation pack.
Tripping and interlocking arrangements
Shunt-trip or undervoltage-release tripping of your nominated circuit breaker, with status indication and volt-free contacts for your control system.
Standard panels for smaller generation
Compact, repeatable G99 relay panels for small solar and battery installations — quick to price, quick to deliver, familiar to DNO engineers.
Engineered panels for larger sites
Bespoke protection panels for larger or multi-generator sites, including CT/VT metering arrangements and integration into existing switchboards.
Commissioning and witness-test support
Relay settings applied and injection-tested before dispatch, with support on the day of the DNO witness test if you need it.
Capability at a glance
| Compliance | Engineering Recommendation G99 (DNO connection requirements) |
|---|---|
| Applications | Solar PV, battery storage, CHP, generators in parallel with the mains |
| Protection functions | Loss of mains, U/O voltage, U/O frequency, per your connection agreement |
| Track record | Systems up to 10 MW, including distributed multi-generator schemes |
| Testing | Settings applied and secondary-injection tested before dispatch |
| Documentation | Settings record, schematics and test certificate — QR-linked on the panel |
Common questions
Do I need a G99 panel?
If your generation runs in parallel with the grid — even briefly during changeover — your DNO will require G99 protection appropriate to the size of the installation. Your connection offer or agreement will state the protection settings required; send it to us and we will quote the panel to match.
What happens at a DNO witness test?
The DNO's engineer watches the protection operate at the agreed settings — typically by secondary injection into the relay — and sees the generation disconnect. Our panels arrive pre-tested with the settings applied, and we can attend site to run the injection test with the DNO present.
How quickly can you deliver a G99 panel?
Standard panels for smaller installations are a stocked, repeatable build — ask for current lead times when you enquire. Engineered panels depend on relay availability and complexity; we confirm a delivery date with the quotation.
Often combined with
Pricing a g99 protection job?
Send whatever you have — a drawing, a spec, or a description of the problem — and we'll come back with a straight quotation: standard panels in hours, complex projects priced properly.