Ian,
Not quite
Voltages used in NI:
Transmission:
275kV (North-South Interconnector also operates at this voltage. Runs 30miles across the border and converts to 220kV at a station in the Republic) 2 X 2000Amp circuits.
110kV (same as the Republic) Rather than 132kV as in the rest of the UK.
There are also two single circuit interconnections at 110kV between Enniskillen – Coraclassey and Strabane – Letterkenny. These cannot be used for trade, but provide system security to electrically weak regions in both jurisdictions.
Distribution:
33kV
11kV
Source: SONI (Systems Operator For Northern Ireland)
A wholly owned subsidury of Virdian Group (this group includes NIE)
Under regulation from OFREG, S.O.N.I. Ltd also manages the commercial agreements with Generation companies and is the facilitator for the emerging energy marketplace in addition to the role of settlements system administrator.
NI is NOT part of the UK national grid system. It operates its own grid independently.
Interconnection:
North-South : SONI - Eirgrid
The main North –South interconnector is a twin circuit 275kV alternating current(AC) tower line, almost thirty miles in length. The connection points are at Tandragee on the NIE system and at Louth on the ESB system. As the ESB system operates at 220kV, intersystem transformers are required - these are situated at Louth.
The circuit ratings are 2000amp and the transformer ratings are 600MVA. There are two sets of first main protection both operating on the distance principle with acceleration – one set runs on BT private wires and the other link is provided by power line carrier equipment.
These circuits allow the two system operators to share spinning reserve requirements, thus saving costs and helping overall system stability. The circuits are also used to trade energy between the two systems by commercial operatives in both jurisdictions.
There are also two single circuit interconnections at 110kV between Enniskillen – Coraclassey and Strabane – Letterkenny. These cannot be used for trade, but provide system security to electrically weak regions in both jurisdictions.
Moyle Interconnector - to GB:
NIE – SP
The interconnection between NIE and SP is carried out using direct current(DC). There are two circuits connecting the two power systems and these are submarine cables approximately 55 km in length.
The cables operate at 250kV DC as two monopolar HVDC transmission systems rated at 250MW per pole, thus providing 500MW transfer capability. The HVDC converter stations are located at Ballycronan More (on Islandmagee in Northern Ireland) and at Auchencrosh (near Ballintrae in Scotland). These converter stations convert the electricity from AC to DC for transmission along the cable and then back to AC again. Power can flow in either direction.
There are two unique features to the equipment involved:-
i) The converter stations are the first in the world designed to use light triggered thyristors(LTT technology). With this technology the thyristors are not triggered by an electrical signal but by a pulse of light – this should make the process more reliable.
ii) The submarine cable design is also a world wide first in HVDC technology as the cables used have a coaxial construction i.e. a metallic ‘return’ conductor is provided as part of one cable.
The link is currently contracted to provide 125MW of power to NI as replacement for NI generation. The rest of the available link capacity (275MW) has been auctioned to energy traders in Ireland.
[This message has been edited by djk (edited 01-10-2006).]
