Case Study

The Moyle Interconnector

Client locations:

Northern Ireland, Scotland
Services: HVDC + Facts
Client/Project Profile:

The Moyle Interconnector (Moyle) is an HVDC link between Northern Ireland and Scotland. Commissioned in 2001, the link provides 500 MW of interconnection capacity between the Northern Ireland and GB electricity grids. The project is a control system upgrade at both converter stations.



TGS is the Client Side Technical Advisor for this project. 

Phase 1 Services:

  • Provision of support for procurement strategy
  • Development of functional technical specifications for the control system replacement
  • Support during the contract development and approval phase

Phase 2 Services:

  • Technical Lead for the control system upgrade project
  • Review design reports from the supplier
  • Witness factory testing at the supplier’s factory
  • Be present on-site to provide support during the commissioning


  • The system had limited reliability due to lack of spare parts for the Control and Protection system; therefore, a new Control and Protection system with state of the art equipment was supplied.
  • There were performance limitations due to the changes in the AC power system; therefore, the Control and Protection system was upgraded as well as some filter banks


The upgrade project was completed on time and on budget despite many challenges caused by the Coronavirus pandemic and the UK Brexit. TGS supported the client (Mutual Energy) and worked together with the supplier (Siemens) closely to overcome many technical challenges.