South Hill Switching Station
South Hill is the strategic hub of our transmission and distribution network, the connection point for Normandie 3 and a potential future fourth cable, as well as accommodating future transmission plant located at La Collette Power Station.
Opened in April 2012, it was built in just 16 months, on time and on budget. However, the speed of its creation was in sharp contrast with its conception.
When the Channel Island Electricity Grid (CIEG) was formed in partnership with Guernsey Electricity in 2000, Jersey Electricity agreed a long-term strategic plan to form a dual 90kV transmission ‘ring’ around Jersey to increase the security of supplies. Planned in stages, it required foresight and a capital budget of an average £10m a year for more than a decade. A switching station at South Hill would complete the ring by connecting our four other primary substations and nine 90kV circuits.
Finding the right site
A substation close to the Power Station was desirable and the old quarry at South Hill was deemed the most suitable plot – being remote enough from the blast envelope of the Fuel Farm, raised above sea level to avoid flooding risk and physically separated from the Power Station but close enough for cabling. Building permission was granted in November 2009 and the site cleared in February 2010.
Fitting the switching station into the site presented huge challenges for two reasons. On the mainland, substations of this size would normally be built outdoors. These installations are not aesthetically pleasing plus, wind-borne salt contamination is a problem on islands.
Our engineers realised that the French design by INEO of St Remy des Landes substation would be the best solution. The design uses air insulated components integrated into the structure of the building. Though, crucially, it means we can carry out our own maintenance and repairs, the technology requires a 25% larger installation.
Minimising the environmental impact
Second, was the desire to minimise the impact of the switching station on the environment. We therefore agreed to base the 39m x 20m x 8m structure two metres below ground, necessitating the removal of 4,000 cubic metres of rock and soil from the site before construction began in earnest in April 2010.
The granite façade further camouflaged the operational nature of the building and landscaping and planting of 150 trees and shrubs minimised the general visual impact.
Almost 18,000 metres of 90kV cabling, manufactured by French company Nexans, was installed by pulling it through through pre-installed ducts that had been laid from South Hill to Tyneville Lane on Victoria Avenue.
With the main external build completed in September 2010, INEO set to work on the complex internal fit-out. The integrated design houses everything required in a transmission substation all in one building: cable terminations, current transformers voltage transformers, line isolators, circuit breakers, bus bars, protection and control equipment and batteries. All this was installed as Geomarine progressed the massive duct laying and cable installation.
Delivered on time and on budget
Both these logistically complicated processes were completed by June 2011 ready for commissioning in July 2011.
Our team of Jeremy Willis (Senior Porjects Engineer, John Duquemin (Chief Engineer), Mark Willie (Senior Maintenance Engineer) and Dominic Warren-Gash (Maintenance Engineer), supported by a number of colleagues, spent a month undertaking various commissioning tests before South Hill was finally energised in August 2011.
The extensive external works, including the laying of 400sqm of dressed granite was completed before the official opening in April 2012 by Lieutenant Governor General Sir John McColl.
JE CEO Chris Ambler said: ‘The delivery of this project on time and budget is credit to a highly skilled, multi-disciplined team and the commitment of our contract partners. It again demonstrates our commitment to investing the capital necessary to provide Jersey with a reliable, secure and affordable supply of energy. As well as enhancing this security, South Hill also exemplifies our desire to integrate our facilities in a sympathetic way within the environment they are situated.’