Scottish and Southern Energy (SSE) has awarded two Thames Valley substation contracts worth a total of £24 million to an ABB and Balfour Beatty consortium. The consortium will design and construct two new indoor state-of the- art gas-insulated switchgear (GIS) distribution substations at Reading, Berkshire and Iver Heath, Buckinghamshire to replace existing outdoor air-insulated switchgear (AIS) substations that are approaching the end of their service life.
A key element in the Reading project will be the use of ABB’s innovative PASS MO switchgear modules to provide a temporary space-saving solution that will free up vital building space. This will enable the new GIS substation to be built in the very restricted space available at the existing site.
The new 132kV substation at Reading and the 66kV substation at Iver Heath are ABB’s first major substation projects for SSE. They play a vital role in SSE’s plans to reinforce its distribution network in the south of England to ensure security of supply and provide additional capacity. SSE regards both sites as flagship projects and asked the consortium to deploy innovative, cost-effective solutions that will enable the new GIS substations to be constructed within the confines of the existing AIS sites.
Vital construction space at Reading
The Reading site is already completely full with AIS switchgear which has to remain in service until the circuits can be transferred to the new substation. The option of expanding into nearby heavily wooded green space to make room for the construction of the new indoor GIS building was rejected because of the planning time, expense and project delays involved.
ABB’s solution uses its proven modular PASS MO switchgear as an interim measure while the new GIS building is built within the existing site. By dismantling old generator circuit-breakers that once served the demolished North Earley power station, just enough space will be freed up for ABB to install its PASS MO modules that will take over the operation of the existing AIS circuits.
When complete, the new 132kV substation will comprise 13 bays with space for four future circuits. After all the circuits have been transferred to the new substation, the temporary PASS MO modules will be removed.
Fast track for Iver Heath
The construction of the new 66kV substation at Iver Heath is more straightforward, as there is already sufficient space on the existing site. The challenge here is to get the new GIS substation on line as quickly as possible. The consortium is placing a major emphasis on planning and logistics.
The Iver Heath site is on the floodplain of the River Colne, so the building is being constructed on stilts to protect it against the predicted level of a once in 100 years flood. This approach has already proved a successful method of flood protection in UK installations. When complete, the new substation will provide six extra bays, taking the total number of bays to 24.