An oral hearing by An Bord Pleanála into plans by Eirgrid to build a new north-south interconnector is underway.
It is expected the hearings in Carrickmacross will last at least six weeks and hear from a range of experts from both the company and the campaign group opposing the scheme.
The plan would see a 140km stretch of new 400 kilovolt overhead line running from Meath to Tyrone.
It would be the second interconnector between the Republic and the North and would, according to the company, secure electricity for the northeast, encourage the provision of renewable energy projects and reduce the need for power stations.
However, there is strong local opposition to the project. The Chairperson of the North East Pylon Pressure campaign, Aimee Tracey, said the plan by Eirgrid was medieval.
She said they accepted the need to upgrade the infrastructure but insisted the cables should be buried underground to alleviate concerns about the health and environmental impact of the cables.
Eigrid say it is not possible to put a cable of that length underground and even if it was it would cause major problems when they would have to carry out repairs or upgrades.
It is likely to be several months before the inspector's report and recommendations are finalised following the oral hearing.
A decision on whether to grant the project planning permission or not will then rest with An Bord Pleanála.
