Planning makes perfect for north London substation

In August 2003, ABB delivered a turnkey design-and-build project for a new 400kV GIS (gas insulated switchgear) indoor substation in north London. The capital’s demand for electricity continues to soar. So as part of National Grid’s ongoing programme to reinforce the power grid serving the London area, ABB is now back on site to carry out the second development phase by adding a further supergrid transformer and associated GIS equipment.

For both National Grid and ABB, the original three-year project was one of the most onerous we had ever undertaken from the planning and the environmental and community impact points of view. The site, in an inner-city urban regeneration area, is particularly challenging, as it backs on to the Regents Canal and the City Road basin, and is surrounded by domestic housing, a school and commercial industrial premises – hemming us in on all four sides.

As turnkey project manager, ABB was responsible for the complete engineering design and civil works, including the construction of the new indoor substation building, and installation and commissioning of the GIS switchgear and ancillary equipment

Before we could even think about construction of the new substation, we had to demolish a four-storey office building. And since the first use of the site dated back to 1720, and it had at some stage been a timber yard, substantial remediation work was required – including the removal of some buried oil tanks.

Dealing with the contaminated land and ensuring that there was no risk of land or water pollution, or dust nuisance, presented a particular challenge. We worked very closely with the relevant environmental agencies to carry out regular sampling. We were also keen to be a ‘good neighbour’ to the local community. This meant keeping noise to a minimum, especially at weekends, and making sure neighbours were fully informed about what was happening through newsletters and letter drops.

The enclosed nature of the site also called for a great deal of advance logistical planning to enable us to move heavy plant, materials and equipment such as 200 tonne transformers in and out, while avoiding traffic disruption to both the roads and the canal, wherever possible. At the peak level, we had around 50 ABB people on site, while also having to direct other contractors.

For the first phase, ABB supplied four GIS switchbays and associated protection and control equipment, together with a 240MVA 400/132kV transformer, and carried out cable diversion work to link the new substation to a substation six miles away in east London. We proved throughout the project that we could help National Grid to meet tight schedules for energisation and final hand-over, while delivering a first class service with minimum disruption. Those were the key factors that enabled us to win the contract for the current two-year extension phase, to supply and install a further supergrid transformer and four more GIS switchbays.

In an excellent example of forward planning, the extension phase was anticipated at the original project stage, so room within the indoor substation had already been allocated for the new equipment, which means that additional civil works have largely been avoided.

One important development from the first stage is that the substation protection and automation systems for the extension will be based on National Grid's standardised NICAP (National scheme for Integrated Control and Protection) philosophy. By using pre-engineered, pre-tested and pre-approved solutions to interface the new bays to the existing substation systems, ABB will be able to achieve significant reductions in the delivery time for this element.

The extension will also see additional cable diversion work to connect the substation to the new indoor GIS substation that ABB has constructed in west London, together with an interconnection to a local MESH substation and connection to EDF Energy’s 132kV substation.