A commercial solar array may be capable of generating more power than the local distribution network will allow the site to export. An approved export limitation scheme can sometimes keep net export within an agreed limit while allowing the business to install and use more generation onsite.
What is G100?
Energy Networks Association Engineering Recommendation G100 sets requirements for customer export or import limitation schemes. These systems control net power flow at the site’s connection point while protecting network safety and supply quality.
Why might export be limited?
The distribution network operator assesses proposed generation against the connection and local network. Unrestricted export may require reinforcement, a smaller system or another design response. In some cases the customer may choose an agreed limitation rather than wait for or contribute to reinforcement.
How does export limitation work?
Measurement equipment monitors power flow at the connection point. The control system adjusts generation, storage or flexible loads so export remains within the agreed limit. The scheme must use appropriate equipment and fail-safe behaviour.
Does G100 mean the solar array is always curtailed?
No. If the business is consuming the generation onsite, little may reach the grid. Curtailment occurs when generation would otherwise push net export above the set limit. The effect depends on the load profile, array size, storage and controls.
Can a battery reduce curtailed generation?
Potentially. A battery may absorb surplus electricity, but only while it has available capacity and sufficient charge power. Its controls must coordinate with the approved scheme. A battery should not be assumed to eliminate all curtailment.
G99 and G100 are not the same
G99 addresses the connection of generation equipment. G100 addresses limitation schemes for import or export. A project may involve both, and compliant equipment does not remove the need for the relevant DNO application and acceptance.
Questions a proposal should answer
- What installed capacity is proposed?
- What export limit is assumed?
- Has the DNO accepted the arrangement?
- Which devices form the limitation scheme?
- How much curtailment is modelled?
- What happens if communications or controls fail?
- Who commissions and documents the scheme?
What information helps?
Half-hourly demand, connection details, single-line diagrams and planned loads help the designer compare onsite use, export and curtailment.
