This however, was not realised until the early 1970’s and it wasnt until 1994, when the contract to supply 4.3MW of hydroelectric power from Llyn Brainne, was finally awarded to Hyder Industrial. The delay was due to the costs associated with connecting the local electricity network to the Grid which were previously thought to be too great to make the project viable.

The site location was very remote and at relatively high altitude in addition to weight restrictions on the access bridge and a constant water spray from the existing reservoir outlets. In spite of this, construction began in January 1996 and was commissioned at the end of the year. The plant was designed by Hyder’s engineering subsidiary, Hyder Consulting, and makes use of water supply infrastructure. Existing pipework was modi?ed to allow water from Llyn Brianne to pass to a purpose-built turbine house at the foot of the dam. The three Francis turbines in the turbine house were supplied by Gilbert Gilkes and Gordon, and have a rating of 2000kW, 2000kW and 640kW respectively. Each drives a synchronous electricity generator of nominally the same rating.

Electricity generated at 650V is transformed on-site to 33,000V via a 600kV ONAN Star/Delta auto tap change unit. It is then transmitted via a 20km underground cable to a local electricity network connection point in Llandovery. The water passing through the turbines is either used for water supply purposes or disposed of as spill. The installation of an advanced telemetry system allows Hyder Industrial to keep a close eye on the scheme 24 hours a day. Operation has generally been trouble-free.

The scheme generates enough electricity to meet the average needs of about 11,500 homes. This equates to annual savings in emissions of more than 28,000 tonnes of carbon dioxide, 384 tonnes of sulphur dioxide and 130 tonnes of oxides of nitrogen, when compared with the equivalent power output from a typical coal-?red power station. Between April 1997 and March 1999 the Llyn Brianne scheme supplied 38,462MWh of electricity to the Grid.