ABB and Balfour Beatty consortium starts work on £12 million contract to build Midlands Electricity’s replacement substation at Port Ham, Gloucester

An ABB and Balfour Beatty consortium has commenced work on a £12 million contract for Midlands Electricity (a Powergen Company) to design and build a replacement 132kV interconnector substation at Port Ham, Gloucester. The use of gas insulated (GIS) switchgear will enable the replacement substation to be housed indoors in a new purpose-built building which will occupy less than one quarter of the space occupied by the existing air insulated (AIS) substation.

The Port Ham interconnector substation is a grid supply point, which feeds electricity from the National Grid substation at Walham into Midland Electricity’s distribution network. This network feeds most of Gloucestershire and Herefordshire and parts of south and east Worcestershire – the equivalent of over one million homes. The existing Port Ham substation, built in the early 1950s, has been subject to above average load growth and its reliability has deteriorated. It is now reaching the end of its useful life and is being replaced to ensure continued reliability of supply.

The traditional approach would be to construct a new outdoor substation alongside the existing substation using similar AIS (air insulated switchgear). This would have required the purchase of additional land. In addition, the outdoor solution presented engineering complexities in order to maintain supplies and meet safety clearances. Midlands Electricity therefore decided on an alternative based on ABB’s state of the art compact ELK- 04 gas insulated (GIS) switchgear housed in an indoor building. This has the advantage of requiring less than one quarter of the space. The site is also in a environmentally sensitive area, being positioned on the edge of a flood plane by the river Severn, and the ABB and Balfour Beatty consortium’s approach to the project offered engineering solutions to meet the required planning requirements to address these environmental issues.



"ABB is proud to be helping Midlands Electricity with this upgrade of one of its key interconnector substations", says Josef Dürr, head of ABB’s Power Systems operations. "The project will provide a perfect example of how the extremely low space requirements and high reliability of ABB GIS combine to offer smart and economic solutions for indoor substations."

In addition to saving space, GIS also offers two further advantages to Midlands Electricity. Firstly, circuit downtime will be reduced as the new circuits in GIS can be constructed with the existing units still in service. So the downtime is then reduced to the re-routing of the network connections. This is crucial due to the critical position of Port Ham in the supply network. In addition, the GIS can be constructed outside the existing live compound thereby considerably reducing Health & Safety risks to personnel working on site. The switchgear will be installed on the first floor of the building to ensure that it is 600 mm above the predicted level of the once in 100 years flooding plain level.


The ABB and Balfour Beatty consortium is providing a complete design, construction and installation service for the new substation, which will feature 20 bays of switchgear and provide a 132kV interconnection for eight incoming and outgoing circuits. It is expected to become operational towards the end of 2006. The existing air insulated switchgear and control room buildings will be demolished.