Grid West High Voltage Direct Current Technology Review


EirGrid pls (“EirGrid”) is a state-owned company that manages and operates the transmission grid in Ireland.  During the development stage of their Grid West project, a major transmission project in the North West to meet proposed plans to connect renewable energy generation, EirGrid investigated the viability of utilising underground cable technology in comparison to overhead transmission lines for this project.  With anticipated cable routes of 112.5km, any proposal to underground the Grid West project would need to consider utilising High Voltage Direct Current (HVDC) technology.


PSC concluded that two solutions that best met EirGrid’s requirements were based on 500MW VSC HVDC links.  The first solution ensured a stable export of new generation from the North Mayo area, whilst the second solution provided greater capacity, but with a higher cost for any future upgrades.

The difference between the two solutions was whether the first monopole was to be built as symmetric or not. The non-symmetric monopole could be converted into a 1000MW bipole by adding a second pole at a later stage whereas to double the capacity of an existing symmetric monopole, it has to be duplicated which would result in higher costs.

Future scenarios were considered that required a further 1000MW being required within ten years to extend the transmission circuit from North Mayo to Casula. The use of voltage source conversion (VSC) technology was preferred over line commutated conversion (LCC) technology because of the weak power system in the North Mayo area.

Specific aspects of the project performed by PSC included:

  • Specialist HVDC technology advice
  • HVDC Transmission options analysis
  • VSC and LCC HVDC project life cycle costing


  • PSC delivered a report on High Voltage Direct Current technology that addressed the key issues and characteristics associated with HVDC technology, and compared and contrasted the various HVDC options that could be viable for these projects. Full project lifecycle costing was provided for each option.
  • This report was submitted to the Irish Government Independent Expert Panel investigating options for the Grid.