ENA EREC G99 Issue 2

Grid-code type testing to G99 Issue 2

The British connection standard for generation above the G98 threshold, and the one that names a variable AC test supply in its own text.

Issue 2 introduced requirements for Power Generating Modules incorporating Electricity Storage that came into force on 1 March 2026. Anyone connecting storage in Britain is inside that regime now.

Why this reaches the test bench

G99 Annex A.7.1.2.2 specifies over/under-voltage type verification carried out by operating the module in parallel with a variable AC test supply, with the test voltage applied in steps of 0.5% or less, held longer than the trip delay, then stepped in a single jump to measure trip time. The document also states that a fully integrated package can be tested in a factory environment, for example on a grid simulator. That is a written-down specification for a programmable AC source.

What gets tested

Interface Protection
LFSM-O
LFSM-U
RoCoF
Fault Ride Through
Vector Shift

Northern Ireland

Northern Ireland runs its own variant: NIE Networks publishes ENA EREC G99/NI. Even within the UK the standard forks.

Normatively referenced

BS EN 50549 series · BS EN 50160 · BS 7430 — British and European documents, none of them American.

How this differs from the American regime

The American equivalent regime is IEEE 1547 with UL 1741 SA/SB — different tests, different trip settings, a different certification culture. A US page cannot serve a British connection application.

Sources

ENA EREC G99 Issue 2 — Energy Networks Association, via the GB Distribution Code site. Retrieved 2026-09-05.Supports: Issue 2, dated 10 March 2025; the storage requirements in force 1 March 2026; Annex A.7.1.2.2 test method

Issue numbers and transition dates move, and several in this field are still quoted wrongly. The compliance calendar tracks the dates that moved, the ones that quietly passed, and thirteen this market repeats wrongly — each against the instrument it comes from.