Eirgrid has defended is proposal to build an interconnector in the north east which would connect electricity grids between the North and South.
Over 900 submissions have been made to An Bord Pleanála relating to the plan for some 140-kilometre of 400 kilovolt overhead line on lattice towers from Meath to Tyrone.
An oral hearing into the plan in Carrickmacross Co Monaghan was attended by hundreds of people as it began this morning. The part of the electricity line within the State will cover 100 kilometres and will pass through Meath, Cavan and Monaghan before crossing the border to a new substation in Co Tyrone.
Residents of the north east, led by groups including the North East Pylon Pressure Group, have previously argued that large pylons and high voltage overhead lines are not appropriate in the area.
They have suggested a number of options including the laying of underground cables along existing rail lines. This would not interfere with animal or human health and would not have a negative effect on farming or tourism, they argue. However, many of the objectors accepted in their submissions that improvement of the electricity infrastructure is needed.
The development is needed to improve electricity competition by reducing constraints to the all island electricity market, to support renewable power generation, to improve the security of supply and to maintain the reliability of the network in the north east, Louis Fisher of Eirgrid said today.
If the interconnector was not built it would put the reliability of customer supply in the north east at risk by 2017, he said.
The second interconnector was also needed in case of an unplanned outage at the existing interconnector from Louth to Armagh which would have serious consequences.
This outage would be cause "widespread disconnection of customers in one part of the system and system instability or even collapse in the other", he said.
The risk and serious potential consequences of power system separation resulted in more expensive generation and higher electricity costs.
There was nothing particularly unusual about this project in its design, construction or operation, said Aidan Geoghegan, a technical specialist with Eirgrid. He said there was no difference between this and over 400 kilometres of line which were already operating safely in Ireland.
However, the masts in this project would have less of a visual impact on the landscape, he said.
He dismissed submissions which said that underground cables should be used rather than overhead lines. Overhead lines were equally as safe and underground cables and underground lines had less impact on the environment, he said.
Forced outage duration of an underground cable would be at least ten times longer than an overhead line because they take significantly longer to repair, he said. While overhead line might take a day or even repair itself the underground cables can take four weeks to fix, he said.
Despite concerns about fatalities with overhead cables there was not a single fatality on overhead cables (110kv, 220kv or 400kv) since records began in 1995, Mr Geoghegan said.
Underground cables were used in specific circumstances such as under the sea as in the proposed Ireland and Wales interconnector. They are also estimated to cost up to ten times more to construct than overhead lines, he said
Eirgrid also dismissed calls for using the route of disused railway lines or placing cables under roads as railway lines and roads in the north east would be too narrow for the development.
The hearing is expected to last until the end of June and in that time local authorities, residents' groups and the Department of the Environment and An Taisce will appear before the board.
