It is located in the Department of Antioquia, 150 km farther east from Medellín, within San Carlos Municipality area, nearby El Jordán rural district. With more than 20 years of commercial operation, is still the largest power plant in the country, 1.240 MW, distributed in eight generation units of 155 MW each, and with proper infrastructure to install two more units. Its first stage (620 MW) started operation in 1984, and the second one in 1987.

Location

Punchiná Dam

Punchiná dam is located over the Guatapé River, nearby the Puerto Bello village. The reservoir has 3,4 km2 reservoir, with a storage capacity of 72 Mm3 of which approximately 53,23 Mm3 are useful reservoir. The dam has an average height of 70 meters over the average level of the river, is 800 meters long, 6 Mm3 of compacted residual soil, with free border at elevation of 781 meters above sea level.

Diversion works and bottom discharge

Diversion of the river during construction was carried out by means of a rectangular section concrete conduit of double body, on the right bank of the river, 414 meters long and 35 m2 of section. One of the sections was blocked off by two sliding floodgates for controlling the flow and thus allowing it to be used as bottom discharge of the reservoir. The other section was sealed off by means of a concrete stopper when the construction of the dam was completed.

Main equipment

The power plant is supervised by the National Dispatch Center (NDC). The NDC computers used for automatic generation control (AGC) and supervisory control and data acquisition (SCADA) communicate with remote terminal units (RTUs) in the machine room to send and receive orders and signals to the generator unit regulators. Communications between the control room and the NDC in Medellin transmitted over a microwave and fiber optic network. The system for supervising and controlling the units is state-of-the-art.

Connection to the National Transmission System, STN (due to its initials in Spanish)

Power generation from San Carlos Power Plant is delivered to the National Transmission System , in order to be taken to consumption centers using two conventional substations, at 230 kV and 500 kV.

Surge tanks

Of restricted orifice type, concrete coated, with a surge absorbent tank 105 meters high, and inner diameter of 13,5 meters in surge tank No. 1 and of 17 meters in surge tank No. 2. They are connected to the pressure tunnels through a shaft 170 meters high.

Shafts and aeration tunnels

Powerhouse ventilation is done by means of a vertical 187 meter high shaft with a round section 4 meters in diameter finishing up with a horizontal tunnel.

Cable shafts

Power cables go out of the transformer cavern through two slope wells at 47°. The San Carlos I's shaft is 270 meters long and has a 7 m2 section. San Carlos II's shaft is 260 meters long and has an 8 m2 section. Either wells finish at the upper part in a horizontal tunnel from where the cables pass to an outgoing structure. From this structure, cables head to the main substation.

Intake works

The reservoir waters are collected through two 54 meter high towers, one of them with round sections 6,30 meters in diameter for San Carlos I, and the other one with 7,50 meters for San Carlos II. The towers, on the right bank of the Guatapé River, are controlled by cylindrical floodgates. Through these towers, flows required for generation are taken to the tunnels by means of two concrete coated vertical wells 147 meters deep each. A metallic bridge joins the operating floors of the towers and allows the movement of the auxiliary floodgates from one tower to the other in a special cart. Each water entrance to the towers is equipped with a strainer grid.

Powerhouse

Powerhouse is composed of two parallel underground caverns located at a depth of approximately 400 meters. The main cave destinated to the generating units is 203 meters long, 19,65 meters wide, and 27,5 meters high. The transformer cave is 203 meters long, 13 meters wide, and 15,3 meters high. Access to cavern through a 1.113 meter long tunnel, with an 8,9% slope, and a double concrete paved pathway.

Shafts and pressure tunnels

Each stage of the plant has an independent conduction with two pressure tunnels 4.474 meters and 4.501 meters of length, and slopes of 1,5% and 0,5%, respectively. The greater part of the tunnels is conventional concrete coated with a round section of 6,1 and 7,5 meters in diameter.

Discharge tunnels

Water leaves the powerhouse and heads to the Samaná Norte River through two discharge tunnels 1.587 meters long and 74 m2 and 102 m2 sections, with slopes of 0,18 % and 0,17 % respectively. The tunnels operate as a free flow conduit for discharges of 132 m3/s and 198 m3/s with a free border of 2,6 meters in the upper section.