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SOGAMOSO
Hydroelectric Power Plant
Civil works
The Sogamoso Hydroelectric Plant is located in
northeastern Colombia, in the department of
Santander.
The dam and all the works that comprise the
project are located in the canyon where the
Sogamoso River crosses the La Paz Mountain
Range, 62 km downstream from the confluence
of the Suárez and Chicamocha Rivers, and 75 km
before it empties into the Magdalena River.
The concrete face rock-fill dam is 190 m high and 355 m
wide at the crest. The elevation at the crest corresponds
to 330 meters above sea level. The fill volume is 8.5
million cubic meters.
The spillway is located on the left abutment of the dam;
it is open-channel and controlled via sluices. Its purpose
is to evacuate excess water when the reservoir’s storage
capacity is exceeded (elevation 320 meters above sea
level). It is designed to evacuate the probable maximum
swell of the Sogamoso River. The spillway consists of a
channel that’s 72 m wide and 354 m long, with gradients
varying between 8.22% and 53.58%, and a wall height
that varies between 10 m and 13 m.
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Installed capacity of
820 MW
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1
It is the structure through which water stored in the reservoir
is withdrawn in order to be transported (through the tunnels
of the penstock system) to the generating equipment housed
in the underground powerhouse. The intake is located 90 m
above the riverbed and consists of a concrete structure with
a grating, and is approximately 110 m long and 25 m high.
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3
In order to control water entry to the penstock system (which carries
water to the generating equipment located in the underground
powerhouse) there is a system of gates, which can be closed for
maintenance or inspection work.
These gates are operated through three 83 m-shafts from an
underground chamber that is 67 m long, 16 m high and 12 m wide
(horseshoe section, straight walls).
After entering via the intake, the water passes through three
conduits that have an upper horizontal 130 m section, a
95 m-shaft and a lower horizontal 180 m section (Average
of measurements between the three conduits). These
conduits have a diameter that varies between 7.2 and
8.4 m, giving them the ability to carry a flow rate of 210 m3
of water, per second, each.
The penstock conduits are concrete-coated, except for the
final part of the lower conduit tunnel, which is reinforced with
steel to ensure resistance to high pressures.
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4
After traveling through the penstock conduits, the water
reaches the generating units housed in the underground
powerhouse’s turbine hall, which contains the control
building and the three generating units that are 15 m in
diameter, weigh 2,618 tons each (turbine and generator)
and all have a 273 MW capacity.
The underground powerhouse is comprised of three rooms:
The aforementioned turbine hall, which is 142 m long,
24 m wide and 49 m high; the transformer room that is
119 m long, 14 m wide and 16 m high, which independently
houses the 324 Mega Volt Ampere power transformers,
and finally, there is the surge chamber, which is 100 m
long, 20 m wide and 43 m high (this is where water is
collected after it has the driven turbines for the power
generation process.
The energy generated in the turbine hall (after passing through the power transformers located in the transformer room) is transferred to the
surface through a vertical shaft that is 120 m high and 3.8 m in diameter. Three power cables (dry, with cross-linked polyethylene insulation,
XLPE) for 230 KV are used for each transformer. Once they reach the outside, these cables come to a gantry-shaped structure and then travel
to the Sogamoso substation where the energy is delivered to the national grid.
Moreover, to facilitate the evacuation of smoke produced by a potential fire or explosion in the transformer room, it has a smoke evacuation
shaft that’s 120 m high and 3.8 m in diameter that exits to the surface.
6
This structure is used to maintain the environmental flow downstream
of the dam when, for technical reasons, the plant is unable to generate
power. This structure was also used during the filling of the reservoir
to ensure the environmental flow.
It consists of a tunnel that’s 605 m long and 7.8 m in diameter
with horseshoe section. It is located on the right bank of the river
Sogamoso, with an adjustable radial gate with a maximum capacity
of 486 m3 per second.
7
The spillway is a structure whose function is to drain excess
water in the event of swells that exceed the reservoir’s
storage capacity. The channel is 72 m wide, 354 m long and
ends in a “ski-jump” deflector. It also has a control structure
with four gates that are 15 m wide by 20 m high, which are
used to control the discharges.
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2
Sluice chamber
1
Smoke and
cable shafts
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5
4
6
Underground
powerhouse
Bottom outlet
7
Spillway
Penstock
conduits
Intake
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Main generating equipment
The Sogamoso plant has three vertical shaft Francis turbines, each rated at 273 MW, with
a speed of 163.63 rpm, a flow rate of 210 m3/s, a nominal net head of 145.53 m, and a
minimum efficiency under nominal conditions of 93%.
Each turbine consists of various components, including the spiral chamber, whose
function is to ensure the uniform pressure of the water it delivers to the distributor, where
there is a cylindrical valve that enables the shutoff or flow of water. There are also the
moving blades and their hydraulic oil system, the speed controller, the turbine runner
(which rotates with a vertical shaft that is coupled to the generator’s lower shaft), and the
shielding for the suction tube, which is responsible for channeling water into the surge
chamber after it passes through the turbine.
The turbine shaft is coupled rigidly to the generator shaft, transmitting the torque to it.
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The generator is synchronous, three phase, 324 MVA, 16.5 kV, has a power factor of 0.9
and is air-cooled. It has a salient 44-pole rotor and vertical shaft, interconnected damper
winding, a guide bearing at the top and a combined guide and thrust bearing at the bottom.
Each generator has a digital static excitation system, which includes the transformer,
connected directly to the busbars, rectifiers, field breaker, and voltage regulator.
Each generator is connected to a power transformer through isolated-phase busbars
made of aluminum and installed inside sealed aluminum enclosures, with a capacity of
12,000 A.
Before reaching the transformer, the busbars are connected to the machine’s breakers,
which are three-pole and utilize SF6 as a means of arc extinguishing and internal insulation.
The rated current is 12,000 A, with a breaking capacity of 130 kA and a breaking time of
less than 67 ms.
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The power transformers are three-phase, OFWF, for operation as a voltage booster, with
two windings, one high-voltage (230 kV) with a star connection to neutral that’s solidly
grounded, and a low voltage winding (16.5 kV) with a delta connection. The rated capacity
is 324 MVA.
Each transformer is located in a separate enclosure in the transformer room. There is also
a backup transformer available for any eventuality.
The transformers are connected on the high voltage side to a circuit consisting of
crosslinked polyethylene insulated cables (XLPE), 230 kV, by means of connection
modules (GIL) immersed in SF6. The cables go up through a shaft until reaching the
surface and a gantry that’s located there, for connection to an overhead circuit that
connects them to the 230 kV Sogamoso substation linked to the national grid (STI).
The cables are made of aluminum and coated in cross-linked polyethylene (XLPE) for
230 kV, they have a 630 mm2 cross-section, forming three (3) three-phase circuits, plus a
backup cable for each unit. These cables exit to the cable gantry through a vertical shaft,
where there is a transition to a 900 Kcmil ACAR bare conductor, by means of composite
terminals (oil-immersed), for connection to the Sogamoso substation.
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The plant has a digital control system with a distributed
configuration (both physically and functionally), an
open architecture, and with manufacturing based
on the latest technologies. This enables growth at
the hardware level and software level, as well as
high availability, reliability and safety thanks to the
distribution of functions and self-checking and selfdiagnostic programs.
All controllers for the control and monitoring system
are redundant in terms of processor, power and
communication cards. They are suitable for working
within a distributed control system and are individually
accessible by any computer connected to the LAN
networks, provided that they comply with the network
security and integrity requirements. The failure of a
processor does not prevent the proper operation of
any of the data paths or devices connected to other
processors.
Connection to the
National Grid
The connection lines between the cable gantry and
the Sogamoso 230 kV substation are 6.7 km long.
The Sogamoso 230 KV substation has a one-and-ahalf breaker arrangement. It receives energy from the
power plant and delivers it to the national grid.