National Grid - G99 connection procedures

Which schemes do the G99 connection procedures apply to?

These processes may be followed where you are installing generation and energy storage installations that are either rated above 16A (3.68kW) per phase or that do not meet the requirements of the current version the Energy Networks Association (ENA) Engineering Recommendation G98.

Where G99 applies, installations must comply with the ENA document ER G99 “Requirements for the connection of generation equipment in parallel with public distribution networks”

Power generating modules with an aggregate capacity ≤50kW 3 phase or ≤17kW single phase

Smaller installations have a simplified process of application

Power generating modules with an aggregate capacity >50kW 3 phase or >17kW single phase

Follow this process if you wish to make an application.

How do I determine the rating of my installation?

I have an inverter, which rating do I use to determine the size of my connection?

Some types of generation (e.g. PV Solar) produce Direct Current (DC) electricity. Where this is the case they have to be connected to our network through inverters which convert the electricity to Alternating Current (AC) before it is connected to our network. The rating of this type of generation is deemed to be the inverter’s continuous steady state rating.

For example, a single phase PV solar installation that uses a 4kW inverter is deemed to have a rating of 4,000 ÷ 230 = 17.39A, which is just over the 16A per phase threshold, assuming the generation operates at a power factor of 1.0 (i.e. unity power factor).

What connection options are available to me?

We have a number of connection offer types we can provide, including a Study & Offer approach which enables you to request that we consider the design solutions for up to 3 different capacities, alternative connections for areas affected by network constraints and traditional connection offers to provide the full requested capacity.

More information is available in the website section Types of Connection Offer Available.

How do I apply?

	Fast Track SGI 1	Fast Track SGI 2	Fast Track SGI 3	Less than 50kW	Greater than 50kW & less than 1MW (Type A)	1MW to less than 10MW (Type B)	10MW to <50MW (Type C)	Greater than or equal to 50MW or > 110kV (Type D)
Applicable Standard	G99	G99	G99	G99	G99	G99	G99	G99
Application	Not Required	Form A1-2	Form A1-2	Form A1-1	Standard Application Form	Standard Application Form	Standard Application Form	Standard Application Form
Notification	Form A3-3	Form A3-2	Form A3-2	Form A3-1	Form A3-1
Evidence	Must be Type Tested	Must be Type Tested	Must be Type Tested	If not type tested- Form A2-1 Synchronous <50kW Or Form A2-3 Inverter connected gen	If not type tested - Form A2-2 Synchronous & Form A2-3 Inverter connected gen	PGMD Form B2-1	PGMD Form C2-1	PGMD Form C2-1
Compliance & Commissioning Checks					Form A2-4 if the interface protection is not type tested or for other site compliance tests	Form B2-2 if the interface protection is not type tested or for other site compliance tests	Form C2-2 if the interface protection is not type tested or for other site compliance tests	Form C2-2 if the interface protection is not type tested or for other site compliance tests
Installation						Form B3	Form C3	Form C3
EON, ION, FON						FON Types B-D: FON obtained during compliance testing & commissioning phase	FON Types B-D: FON obtained during compliance testing & commissioning phase	ION, EON, FON For Type D only: ION & EON obtained during Energisation Planning phase

All application forms can be found on the ENA website here.

Power generating modules with an aggregate capacity >50kW 3 phase or >17kW single phase

Please complete the G99 standard application form. As a minimum, parts 1-3 should be completed at application stage. Parts 4 and 5 shall be completed where the information is available and, in any case, should be submitted prior to the connection being made.

Power generating modules with an aggregate capacity ≤50kW 3 phase or ≤17kW single phase

Where the power generating module is fully type tested and registered in the ENA Type Test Verification Report Register, application form A1-1 should be completed.

Where the power generating module is not type tested or only part type tested, application form A1-1 should be completed and submitted along with one of the following forms (as appropriate):

A2-1 Compliance verification report – tests for Type A synchronous power generating modules up to and including 50kW – test record
A2-2 Compliance verification report for synchronous power generating modules >50kW and also for synchronous power generating modules ≤50kW where the approach of this form is preferred to that in Form A2-1
A2-3 Compliance Verification Report for inverter connected power generating modules

G99 Fast Track

For G99 Fast Track processes please click here.

Witness testing

Engineering Recommendation G99 sets out the requirements for commissioning tests and checks. It is the responsibility of the installer to undertake these tests and ensure the generation units meet all the relevant requirements.

In some instances, we may need to witness the testing which will incur a fee. For further information regarding our fees please click here. We will notify you in advance should a witness test be required.

Further Guidance