Monday 20 November 2017

Underground cables 'would cost €1bn more than pylons'

A protest outside the Dail against the siting of pylons in the Comeraghs
A protest outside the Dail against the siting of pylons in the Comeraghs
Ralph Riegel

Ralph Riegel

THE cost of developing a new high voltage power line between Cork and Dublin could soar by €1bn if it is placed entirely underground.

The Irish Independent has learned that the 250km high-voltage electricity grid extension could end up costing €1.5bn – three times the estimated cost of erecting the lines above ground on traditional pylons.

EirGrid will present two alternatives for the Cork-Kildare/Dublin network in September, one of which will be underground and the other one above ground.

The proposals will be submitted to an independent panel, which will then report to the Government with specific recommendations. A final decision on the type of network extension and its precise route will be made in July 2015.

The network must run between Cork, Wexford and Kildare but its precise route has not been finalised.

However, EirGrid is now battling to try to reduce the cost of placing the network extension underground amid fears by energy expets that the cost could reach as much as €1.5bn.

Residents in Cork and Waterford have already campaigned against the proposed above-ground option due to its reliance on up to 250 pylons, some of which, for topographical reasons, may extend to 75 metres in height. This is as tall as Croke Park.

The Comeraghs Against Pylons (CAP) group warned that the erection of such pylons across the narrow 7km strip between the Comeragh Mountains and the Waterford coastline would devastate an area of immense natural beauty.

CAP official John McCusker claimed that it would also jeopardise a UNESCO 'GeoPark' at the Copper Coast between Dungarvan and Tramore.

Residents in Knockraha in east Cork have also campaigned against the pylons.

The pylon alternative for the 400KV grid extension is estimated to cost between €500m and €700m.


However, EirGrid is battling to try to reduce the cost of placing the network underground in order to keep it competitive with the pylon option.

The problem is that electricity cannot be economically transferred underground in its normal high voltage alternating current (HVAC) format.

It is transferred in high voltage direct current (HVDC) format in three major cables which are buried in concrete in a trench parallel to major roadways.

However, the transfer of electricity in HVDC form requires special converter sub-stations at every major power station.

Each station costs €250m to construct – and there are concerns that the Cork-Wexford-Kildare network may require as many as four conversion stations at a total cost of €1bn.

"That is before a single metre of cable is laid underground," one source said.

There are also concerns that the cost of accessing underground cables for repairs and the length of time such repairs can take are both higher than the overground option of pylons.

However, the independent panel have the power to recommend a 'mixed' grid extension with a largely overground pylon link supplemented by underground cabling in specific areas. These could be used to try to ease residential or environmental concerns.

Irish Independent

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