First Hydro Company
Dinorwig Power Station
When it was fully commissioned in 1984, Dinorwig Power Station was regarded as one of the world's most imaginative engineering and environmental project.
Today, Dinorwig's operational characteristics and dynamic response capability are still acknowledged the world over. Dinorwig is the largest scheme of its kind in Europe.
Dinorwig is comprised of 16km of underground tunnels, deep below Elidir mountain. Its construction required 1 million tonnes of concrete, 200,000 tonnes of cement and 4,500 tonnes of steel.
The station's six powerful generating units stand in Europe's largest man-made cavern. Adjacent to this lies the main inlet valve chamber housing the plant that regulates the flow of water through the turbines.
Dinorwig's reversible pump/turbines are capable of reaching maximum generation in less than 16 seconds. Using off-peak electricity the six units are reversed as pumps to transport water from the lower reservoir, back to Marchlyn Mawr.
DINORWIG FACTS & FIGURES
Surge Pond Data: | |
| Dimensions of surge pond | 80x40x14 metres deep |
| Diameter of surge shaft | 30 metres |
| Depth of surge shaft | 65 metres |
Generator/Motors: | |
| Type | Vertical shaft, salient pole, air cooled |
| Generator rating | 330 MVA |
| Motor rating | 312 MVA |
| Terminal voltage | 18kV |
| Excitation | Thyristor rectifier |
| Starting equipment | Static variable frequency |
Generator-Motor Transformer: | |
| Number | Six |
| Approximate rating | 340 MVA |
| Voltage ratio | 18 kV/420 kV |
Underground Caverns: | |
| Distance of power station inside mountain | 750 metres |
| Depth of turbine hall below top level of Llyn Peris | 71 metres |
Machine Hall: | |
| Length | 180 metres |
| Width | 23 metres |
| Height | 51 metres max |
Transformer Hall: | |
| Length | 160 metres |
| Width | 23 metres |
| Height | 17 metres |
| Diversion tunnel length | 2,208 metres |
| Width | 6.5 metres |
| Height | 5.5 metres |
| Maximum flow | 60 cubic m/s |
| Normal flow | 1-8 cubic m/s |
| Fall | 1:1500 |
Pump/Turbines: | |
| Type | Reversible Francis |
| Number | 6 |
| Plant orientation | Vertical spindle |
| Average pump power input | 275 MW |
| Pumping period (full volume) | 7 hours |
| Synchronous speed | 500 rpm |
| Average full unit over all heads (declared capacity) | 288 MW Generation potential at full load |
| Output | 5 hours |
| Station power requirements when generating | 12 MW |
| Standby operational mode | |
| Synchronised and spinning-in-air emergency load pick-up rate from standby | 0 to 1,320 MW in 12 seconds |
Transmission Switchgear: | |
| Type | SF6 metal clad |
| Breaking capacity | 35,000 MVA |
| Current rating | 4,000 A |
| Voltage | 420 kV |
Excavations: | |
| Main underground excavation | 1 million cubic metres (approx. 3 million tonnes) |
| Total scheme excavations | 12 million tonnes |
