|
|
Hydro-electricity generation at Llyn Brianne
Although the generation of hydro-electricity (HEP) at Brianne has always been an option, it was not until 1990 when the government introduced its Non Fossil Fuel Obligation Renewables Orders (NFFOs) that it became a viable proposition for Welsh Water. A 4.35 Megawatt supply contract was obtained by Hyder Industrial in January1995. The scheme involved raising the sill of the Dam by one metre for better management of the water resource, and introducing three HEP turbines into the dam outflow. The operational system operates with one small 600 kw turbine running on the continuous (15 mgd) Compensation Flow, and the two large 2.5 MW machines operating mainly during periods of potential overspill following high winter rainfall, between 1st November and 6th April. They also generate under Prescribed Flow augmentation conditions, and during any extra releases made in order to dilute acidic flows into the Towy from the Doethie, a major upper river tributary.
The original 1650 mm (66 inch) steel outflow sub-divided into three branches each with a 625 mm (30 inch) blanked off inspection flange. This left the HEP engineers the simple task of fabricating a manifold for connecting up the turbines. This 1350 mm (53 inch) pipe weighed 12.5 tonnes.
The generation voltage is 660 volts which is transformed on site for transmission 20 miles underground to the Grid connection at Llandovery
