Going underground

Going underground

Space is at a premium when building new infrastructure or delivering upgrade projects in congested city centres. The high value of the land makes it difficult to acquire suitable sites and obtaining planning consent can often be a major challenge, as well as extending project timelines.

The logical thing to do is to dig down, putting the substation below ground level and freeing up land on the surface for commercial, transport and public uses. ABB’s underground substation concept means that 98 percent of an installation can be hidden out of site below ground level, leaving only access points and cooling ducts visible.

Substation equipment

As a result, the functionality of a transformer substation can be hidden underneath buildings, parks and roadways. Such substations include equipment such as transformers, GIS, protection and control systems, AC and DC distribution boards, energy storage and backup batteries.

These are complemented by the essential safety provided by ventilation, air-conditioning and fire protection systems, as well as escape routes for operators.

In fact, ventilation equipment is one of the most important considerations. Under ABB’s approach to underground substations, the temperature profile of the environment is balanced against the needs of the equipment. In addition, ducts are sized to control air velocity so that noise emissions fall inside the permitted levels.

All city centre construction projects need careful planning and scheduling to minimise disruption, for example by ensuring faster completion, planning major deliveries to take place overnight, or by controlling the levels of noise and dust experienced by neighbours.

Operation, maintenance and extension

However, the life of a substation only starts when the construction phase ends. Equipment will need to be serviced and maintained throughout its life.

As a result, it’s vital to plan for replacement and extension of substation equipment. In particular, it’s important to allow space for the eventual lifting, removal and replacement of the power transformers, as well as oil servicing.

Two basement levels for London Underground

In the UK, ABB helped London Underground Limited make the most of a compact site when delivering a new Bulk Supply Point for the Circle, District, Hammersmith & City and Metropolitan lines. ABB excavated 11,000 cubic metres of spoil and carried out piling next door to the live railway line to create two basement levels to house switchgear and sophisticated cabling, with other equipment including grid transformers being located at ground level and above.

Delivery of the power transformers to the central location was scheduled in advance in the early hours of two Sunday mornings to minimise the impact of road closures.

ABB created two basement levels at this London Underground substation

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