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G99 connection procedures

  • 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 where you have already connected, or are proposing to connect, other G98 compliant generation installations within a local geographic region* within 28 days of this application.

  • The aggregate rating of the generation is deemed to be the sum of the rating of each generator at the premises. No consideration is given to whether or not they are likely to be operating at maximum capacity at the same time.

    The rating of each generator is deemed to the Alternating Current (AC) rating of the generator. Ratings expressed in watts or kilowatts are based on the nominal voltage. For generation connected to our low voltage network the nominal voltage is 230V (between phase and neutral).

    For example, a 3 phase generator with a rating of 50kW that is designed to be connected to our low voltage network has a current rating of 50,000 ÷ (230 x 3) = 72.46A per phase, assuming the generation operates at a power factor of 1.0 (i.e. unity power factor).

  • 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).

  • 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.

  • 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

    A fast track process is available to installations onto a single phase connection whereby two inverters will be connected, but export will be limited, and a number of pre-determined eligibility requirements can be met. This may include requests to;

    a) Install a battery storage device via a separate ER G98 type tested inverter at premises with existing PV installation (or other DG type that confirms with ER G98); or
    b) Install a new PV (or other DG type) scheme and battery storage via two separate G98 type tested inverters.

    You will be eligible provided you can reply yes to each of the following:

    1. Are you applying to connect at a single property?
    2. Is the combined installed capacity of your generation and battery storage devices less than 32A per phase?
    3. Is the individual capacity of each of your generation and battery storage devices less than 16A per phase?
    4. Will your export capacity be limited to a maximum of 16A per phase via an export limiting device that is compliant with ER G100.
    5. Will both your generation and battery storage devices be connected via ER G98 type tested invertors?
    6. Will both your generation and battery storage devices be prevented from operating in island mode, i.e. when there is no mains supply?

    When utilising the fast track process for eligible schemes, we aim to provide you with a decision regarding the ability to proceed with the installation with 10 working days.

    To apply, please complete Form A1-2, Application for Connection of Fully Type Tested Integrated Micro-Generation and Storage Installations.

  • 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.