The Miel I Power Plant is located in the Municipality of Norcasia. It generates a portion of the hydroelectric power in west Caldas, where major water sources include the Guarinó, La Miel, Moro, Manso and Samaná Sur Rivers and minor tributaries such as the Pensilvania and Tenerife Rivers. The Power Plant has an installed capacity of 396 MW in three units. In isolated operation, it can generate 1,135 GWh of firm energy/year, and an average of 1,638 GWh/year when the Guarinó Diversion is used to supplement the natural river flow.

Location

Patángoras Dam

At 188m high, this is one of the tallest dams in the world, built from Roller-Compacted Concrete (RCC). It is a gravity type dam with a spillway. It is built over the Miel River, downstream from the mouth of the Moro River, forming the 1,220 hectare Amaní reservoir, which has a storage capacity of 571 Mm3. The dam crest is 340 meters long, 454 meters above sea level, and the reservoir's normal level is a maximum of 445.5 meters above sea level. The dam volume is 1.73 Mm3.

Diversion and bottom discharge structure

For the dry construction of the dam, the river was diverted by means of a tunnel located on the right bank, 550 meters long and with rectangular section with circular vault of 10,8 x 10,8 meters without coating, which was sealed off when the construction of the dam was completed. The bottom discharge is composed of a collecting structure and a well that feeds two parallel tunnels. Flow into the tunnels is controlled by Butterfly and Howell Bunger valves. It is able to discharge up to 250 m3/s and will allow discharge of the ecological flow whenever required.

Water inlet and pressure tunnel

The inlet and pressure tunnel are located on the left bank of the river. Control of charge tunnel is made by means of two floodgates installed in the floodgate well, located 68 meters from the entrance. The floodgates are operated by means of servomotors located in the upper part of the well. The upper charge reinforced concrete coated tunnel is located after the inlet; it is 90 meters long and has a diameter of 6,55 meters. Next, there is a vertical reinforced concrete coated elbow type joint connecting with the charge (vertical) well, 119,20 meters deep. The 58 meter long interior tunnel includes a reinforced concrete coated section and a steel shielding 45 meters long. From that point on, there are two metallic bifurcations connecting with the three inferior tunnels 3,35 meters in diameter that conduct water to the machine cave.

Powerhouse

The underground powerhouse is located on the left bank of La Miel River and is composed of three caverns, from upstream to downstream, including machine, transformer, and surge tank.

Machine cavern

The main cavern is 19,3 meters wide, 86,5 meters long, and 38,8 meters high, and hosts 3 Francis turbines with their corresponding generators and auxiliary equipments. It has permanent and forced ventilation through horizontal galleries and from the ventilation well located northwest from the cavern.

Transformers cavern

The transformer cavern hosts three 150 MVA step up transformers. The transformers' 230 kV dry cables exit through a gallery and a well up to the cable portico, on the foothill. From these porticos two aerial lines leave, one single circuit, the other double circuit, up to Miel I substation.

Surge tank

It is located downstream from the machine cavern and serves to collect discharges from the turbines and as shock absorber of pressure caused by the normal machine operation. The cavern is 52 meters long, 15 meters wide, and 44,5 meters high.

Discharge tunnel

It is located on left bank of La Miel River and returns its waters into the same river. The discharge tunnel of 9,0 meters and 9,05 meters section begins next to the surge tank and is 4,1 km. long with a concrete crossbeam with pneumatic concrete coating. At the exit, it has a reinforced concrete structure with guides for metallic planks.

Main equipment