Customer Connections – Policies

EirGrid, as a Transmission System Operator (TSO), plans, manages, develops and operates the national electricity transmission grid at 110, 220, 275 and 400kV across the island of Ireland.

EirGrid develops and maintains Transmission Investment Policies setting out the acceptable standards and regulations for transmission developments.

Below is a non-exhaustive list of policies that may be of interest to customers seeking connections. EirGrid considers it appropriate to engage with stakeholders when the development of new or changes to pre-existing technical standards and policies pertaining to transmission equipment and installations are proposed which could result in a significant increase in customer project costs or planning requirements. Following conclusion of a period during which stakeholder feedback was invited by 26 February 2021, EirGrid has finalised its engagement process for development and update of technical standards and policies which sets out the steps that EirGrid will follow in these circumstances here.

Transmission Policy Documents

  1. Access to TSO Current and Voltage Instrument Transformer Cores
  2. Policy on Wind Turbine Clearance to OHL’s
  3. Policy on Calculation of the Maximum Fault Level for Substation Earth Grid Design
  4. Policy Statement on Busbar Configuration for 110, 220 and 400 kV Transmission Substations
  5. Transmission Line and Solar Farm Guideline Clearances
  6. Options for Connecting Customers to the Transmission Network  

Customer Connections – Technical Standards

EirGrid maintains and develops technical standards, including functional specifications and standard drawings that are available to assist Customers proposing to connect to the Irish transmission system. These technical standards govern the design and construction of new transmission assets namely transmission substations, cables and overhead lines as well as providing guidance when developments are proposed in proximity to existing transmission infrastructure.

Below is a non-exhaustive list of commonly used technical standards for demand and generation customers to consider when developing their connection projects and associated planning applications.

Functional Specifications:

  1. 110/220/400kV Station General Requirements (XDS-GFS-00-001-R4)
  2. 110kV/220kV/400kV Underground Cable Functional Specifications (CDS-GFS-00-001-R1) - New May 2021
  3. 110kV Underground Cable Drawings
  4. 110/220/400 kV GIS Functional Specification (XDS-GFS-25-001-R4)- Currently Under Review
  5. Control, Protection and Metering Functional Specification (XDS-GFS-06-001-R2)
  6. Station Auxiliary Power Supplies Functional Specification (XDS-GFS-08-001-R3) - New Feb 2021
  7. Earthing and Lightning Protection (XDS-GFS-12-001-R4) and associated drawings (XDS-DGA-00-004-R04)
  8. Station 220 V, 48V and 24 V Lead Acid Batteries and Chargers (XDS-GFS-09-001-R4)
  9. Instrument Transformers (110, 220 & 400 kV) Functional Specification - Currently Under Review
  10. Substation Civil and Building Works (XDS-GFS-13-001-R2) - Currently Under Review

Standard Layout Drawings:

  1. 110 kV AIS Substation Layout Drawings – 8 Bay (XDN-LAY-ELV-STND-H-001-R08) - New Feb 2021
  2. 110kV AIS Single Transformer Tail Station (XDN-LAY-ELV-STND-H-003-R04) - New July 2021
  3. 110 kV Single Bay Extendable to C-type station (XDN-LAY-ELV-STND-H-006-R00) Currently under review
  4. 110kV AIS Station Typical Control Room Layout (XDN-CR-STND-H-001-R01)
  5. 110 kV GIS Station Layout (8 Bay) (XDN-LAY-ELV-STND-H-005-R00)
  6. 220 kV GIS Substation Layout Drawings: Single bay (XDN-LAY-ELEV-STND-F-002-R00), 8-Bay (XDN-LAY-ELEV-STND-F-005-R00) and 12-Bay layout (XDN-LAY-ELEV-STND-F-004-R01)

Standard Single Line Diagrams:

  1. Customer 110kV AIS C-Type SLD (XDN-SLD-STND-H-005-R03) - New July 2021
  2. Customer 110kV GIS C-Type  SLD (XDN-SLD-STND-H-006-R02)


It should be noted that requirements can change based on new technologies, safe working standards or lessons learned during construction, operation and decommissioning. There are a wide variety of potential transmission connection solutions. The standard layout drawings provided here are concept designs of the most commonly acceptable solutions and are provided for guidance only.

AIS substations comprise of open-terminal air –insulated switchgear, whereas GIS substations comprise of metal enclosed gas-insulated switchgear. In GIS substations the switchgear is located in a building. In the case of AIS substations the switchgear is generally located outdoors.

Detailed project specific documentation is provided to applicants who have executed a connection offer with EirGrid.

EirGrid will work with customers and provide technical assistance with their planning drawings to incorporate technical feedback in advance of finalising their planning submissions. Customers are encouraged to check that they are using the most up-to-date information.

For further information on the connection offer process, please refer to this page on becoming a customer

For customers currently engaging with EirGrid in the connection offer process, further detailed specifications and standards can be made available on the EirGrid Extranet page. (Requests for access to the EirGrid extranet page for Transmission standards should be submitted to


Information provided to customers on this website contains general and technical information, which is subject to change from time to time without notice. EirGrid makes no warranties or representations of any kind with respect to the general and technical information provided or the content of any other document or website referred to on this website. EirGrid cannot determine any proposed connection methods until the formal connection application process is completed. Until an application is submitted and the relevant detailed studies and an executed connection agreement are complete, EirGrid will not be in a position to confirm specific technical details. Customers should not act or refrain from acting on the basis of any information provided without seeking appropriate professional advice.

Use of the information provided is solely at the user's own risk. EirGrid does not accept liability for any loss or damage arising from use or reliance on the information provided.