The current major project to create a new Bulk Supply Point (BSP) for London Underground (LU) provides a perfect example of ABB’s capability to deliver a complete design, project management and construction service for rail substation projects.
This capability that not only includes all the electrical equipment, but also cabling and the very substantial civil works required to create a new substation building within an extremely restricted footprint.
Transport for London (TfL) has a number of existing 132 kV BSPs that supply power for LU. This additional BSP is now needed to increase the available power to support the full operation of new air-conditioned rolling stock that, since 2010, is being phased in on the sub-surface (SSL) lines – the Circle, District, Hammersmith & City and Metropolitan.
The BSP’s desired 120 MW capacity dictated that it should be located relatively close to a grid supply point. It also had to be located close to the LU infrastructure in order for the necessary cable connections to be made between it and the existing distribution system. The most appropriate site for the new BSP substation was identified adjacent to an underground station.
Restricted site
The new BSP is designed to take electricity from a nearby National Grid 400/132 kV substation (constructed by ABB in 2004) and step it down through transformation (132/22/11kV) to feed into the LU power supply system. In the past there were houses and shops on the site, but they have been long since demolished and most recently, the site was used as a car park. The major challenge for ABB has been in working within this restricted site, hemmed in on all sides with an operating railway close by, to create a large, modern substation building.
The project commenced in 2009, and ABB has focused on the excavation and civil works to create a new cable and switchgear basements and multi-level reinforced concrete building. The scale of this exercise is illustrated by the need to remove 11,000 cubic metres of spoil materials – some 2,300 lorry loads. Extensive deep piling has also been carried out to create the foundations. This level of civils work in a busy area of London has called for a very detailed approach to logistics and communications, not only with contractors and travel authorities but also in ensuring minimal disruption for the local community.
Electrical equipment
Following completion of the civil works, ABB moved on to install the electrical equipment. This includes: three 22/11 kV 25 MVA coupling transformers; two 132/22 kV 120 MVA grid transformers; a 35 panel 22 kV switchboard featuring ZX2 GIS (gas insulated switchgear); a 27 panel 11 kV switchboard featuring UniGear AIS (air insulated switchgear); LV switchgear; two 11 kV earthing / auxiliary transformers; ventilation system and associated mechanical systems; 110 V batteries and charger.
A major project milestone was the successful delivery and installation of the two grid transformers, each weighing 97 tonnes, completed over two weekends at the end of 2011. Transporting the transformers into the centre of London and manoeuvring them into position was a highly complex logistical exercise requiring months of planning with ABB’s transportation partner ALE (Abnormal Load Engineering) to develop the optimum installation methodology.
Stakeholder management
Equally important was detailed attention to stakeholder management. This involved working in close liaison with the local council, police and residents to identify the best route, arrange the necessary road closures, traffic diversions, suspension of parking spaces, removal of traffic lights and signs to enable the two massive loads to reach the site with minimum disruption.
The substation is also being provided with new SCADA RTU (remote terminal units) for the 11 kV and 22 kV switchgear. Extensive fibre optic cabling will be installed to provide the communication path between the BSP, other substations and the LU control centres.
In its first large scale cabling exercise for LU, ABB is also carrying out cabling works associated with the BSP including around 55 km of 22 k and 11 kV XLPE cable installed in tunnels and ducts.
The new BSP project is scheduled for completion in the summer of 2012.