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Nuts and Bolts

There are four principle components in the construction of Pole 3, which occur in parallel at the Haywards and Benmore substations:

  1. Civil work
  2. Construction of buildings
  3. Primary plant installed
  4. Construction of switchyards

Civil work

Only minor civil work is required at the Benmore substation to prepare the site for construction of the buildings and equipment for Pole 3 (compared to the larger amount civil works required at Haywards). This is because the substation at Benmore is on comparatively flat land and has adequate space available for the Pole 3 works.

Construction of foundations and excavation for the switchyard gantries comprises most of the civil work needed at Benmore.

Construction of buildings

From May 2010 to July 2011 the valve hall control room buildings will be constructed. Three thyristor valves that weigh 20 tonnes each will be suspended from the ceiling of the 19 metre high valve hall.

The control room houses the cabinets and servers that automate the operation of Pole 3.

Installation of Primary plant

Primary plant consists of the major pieces of equipment needed to convert AC to DC and back again. This includes the thyristor valves - housed in the valve hall - and converter transformers that are outside the valve hall and weigh up to 330 tonnes each. Six-metre long bushings transfer electricity between the transformer and the valve.

The primary plant will be installed between July and December 2011, ready for testing to begin in December and full operation in April 2012.

Construction of switchyards

The existing AC and DC switchyards will be expanded to accommodate the additional lines that are needed within the switchyard. Switchyards contain the lines and structures that support the lines within the substation grounds.