EMAT 6690
This is the contextual learning assignment
for EMAT 6690.
By Kimberly Burrell,
Brad Simmons, and Doug Westmoreland
Please click
here for an overview of electrical terms that are used in
this document.
North Georgia Hydro
The Tallulah Falls Hydroelectric Plant is the
oldest and largest in the North Georgia Hydro Group. The land
on which the plant stands was purchased before 1905 by the North
Georgia Electric Company. In 1912 the Georgia Power Company, which
purchased the North Georgia Electric Company in 1910, merged with
several other utilities that could use the plant's capacity. This
formed the Georgia Railway and Power Company. The plant first
began operating in 1913. In early 1914 all five of the 12,000
kilowatt generating units were completed, and Tallulah Falls became
the third largest hydroelectric facility in the United States.
The sixth generator was not added until 1919 and the output was
brought up to present day which is 72,000 kilowatts.
The Tallulah River is damed just above the
falls by a 126 foot high by 426 foot wide dam. Water is directed
into an intake structure on the river bank and into a horseshoe-shaped
tunnel that is 11 feet wide and 14 feet high. The tunnel is 6,666
feet long and is cut through solid rock. This tunnel takes the
water to the forebay which is on the side of the gorge above the
Tallulah Power Plant. The water is then passed into six penstocks
that deliver the water down the gorge to the powerhouse.
The map above shows the lakes and dams
that along with the hydro plants located at the dams that make
up the North Georgia Hydro Group.
THE TOUR
February 3, 2001
The railway track shown to the right
of the six penstocks is the primary mode of transportation in
and out of the power plant located in the bottom of Tallulah Gorge.
All the materials and equipment used
to construct the power plant were transported into the gorge by
the railway. The railway is still the mode of transport for all
equipment used for maintenance, repairs, and physical changes
to the power plant. Kim Burrell is standing next to the maintenance
car used today. Brad Simmons, Kim, Doug Westmoreland, and plant
operator Jeff Moore are standing behind the original 1914 motor
used to power the cable car which is still in use today. The maintenance
car is controlled from this hoist house located at the top of
the gorge.
The power plant operates three shifts
a day year round. There are three operators working in the plant
at all times. These operators travel in and out of the gorge in
the German manufactured passenger car shown in the upper left
picture. This car uses the same track as the maintenance car.
It takes the passenger car 8 minutes and the maintenance car 20
minutes to make the descent to the bottom of the gorge. The picture
on the upper right shows the walkway leading to the top of the
railway track.
Since the passenger car is controlled
from the control shack at the bottom of the gorge, Jeff Moore
informed the operator in the plant that we were ready to begin
our descent into the gorge.
"Cut the Rope
... "
The picture above is a view from the
top of the track.
The picture on the upper left is a
view as we are descending. The picture on the upper right is a
look back up the track as we approach the bottom of the gorge.
On the upper left is another look back
up the track as the passenger car reaches our destination at the
power plant. The picture on the upper right shows the small control
shack on the concrete deck outside the plant from where the passenger
car is controlled. Please notice that the track continues into
a hole under the concrete deck. Since the passenger car and the
maintenance car use the same track, the passenger car must be
placed down in this hole in order to clear the track for the maintenance
car to be used.
Doug, Kim, and Brad have survived their
ride into the gorge and are ready to enter the powerhouse.
Southern Company employees and visitors
enter the plant through the door, but the water enters through
the six penstocks. The next three pictures show the penstocks
as they get closer to the powerhouse.
Because of the drop in elevation from
Tallulah Falls lake to the bottom of the gorge the water pressure
builds to 250 pounds per square inch (psi) at the point where
the 60 inch diameter penstock feeds into the generating unit.
This water pressure enables the generating unit to produce electricity
with a minimal water flow of 300 cubic feet per second (CFS).
If we compare this volume to the 1800 CFS it takes to produce
electricity at the Tugalo Plant down stream, it is easy to see
the benefit of having gravity build the water pressure in the
penstocks.
The picture above shows the penstock
as it feeds into the bottom part of the generating unit. Once
inside the unit, the water travels in a circular path which causes
the generator to turn.
This gauge measures the water pressure.
We can confirm that the water is under 250 psi as generating process
begins.
Even though the water enters the generators
at the bottom of the powerhouse, these large generating units
extend up into the next floor of the plant. The picture above
shows the lower part of one generating unit. To see the remainder
of the unit, one must walk up the stairs to the next floor of
the plant.
As the generator turns, the bearings
ride on a thin layer of oil that must be very closely monitored.
Once the water passes through the generating
unit, it is then expelled out into the gorge and flows into Tugalo
Lake.
Please notice in the picture above
the water between the powerhouse and the rock wall on the left.
This water has been used for power generation. The water to the
left of the small rock wall has not been used for power generation.
By federal law, at least 35 CFS of water must be in the gorge
at all times. Therefore, a 30 foot pipe was constructed in the
Tallulah Falls dam to feed water directly into the gorge. This
is the only water from Tallulah Falls Lake not used for power
generation. However, twice a year water levels in the gorge are
increased above 35 CFS for recreational purposes.
The control unit pictured above is
located just outside the powerhouse. It monitors the water flow
through the gorge and the data that is collected is used to report
to the federal government.
The picture above shows the top part
of five of the generating units.
Each generating unit has a governor
that controls its speed.
Each generating unit is air cooled.
Although Kim, Brad, and Doug are still inside the plant as they
stand near the top the this generating unit, the strong breeze
from the units air cooling system is evident as it blows up toward
the ceiling of the plant.
The picture above gives us an idea
of how large these unit are. Jeff is standing on the floor as
Brad and Doug look through a small glass window and observe the
circulating oil which is critical for the unit to run properly.
Here we see a picture of the information
plate that is displayed on each of the six generating units. These
alternating current generators produce 12,000 kilowatts which
is equal to 12 megawatts of electricity. At a speed of 514 they
produce 6600 volts and 1050 Amperes.
After climbing one more flight of steps
from the generating room floor, we entered the control room. This
is where the plant operators do the majority of their work. From
this room the operators monitor and control every generating unit
in the North Georgia Hydro Group with the one exception of the
unit at Burton Dam.
The entire power group which includes
hydro plants at Burton, Nacoochee, Terrora (Mathis Dam), Tallulah
Falls, Tugalo, and Yonah is linked together by a computer system
that has been online for the last four or five years. Bruce Taylor
is looking at the white monitor on the right which is part of
this new system. The old Hewlett Packard computer on the left
is still the only means to control the generating unit at Burton
Dam from this Tallulah Falls control room.
Doyle Parker is showing Doug and Brad
the old manual controls and gauges that were the only means to
monitor the plant at one time. These gauges and controls can still
be used in the case of a computer problem that may arise.
The operators must keep detailed log
sheets for not only power generation but for lake levels and water
flow in the gorge. The goal is to keep the water in the lakes
full during the summer recreation period. In the fall, the lake
levels are reduced in order to give residents on the lake an opportunity
to repair boat docks and take care of other general maintenance.
The ability to monitor the weather at all times is very important.
One thunderstorm could force the operators to completely rework
their power generation schedule.
Timing is critical in opening the gates
that lets water into the generating unit and past the dam because
if any lake gets overfilled the excess water will be lost over
the dam. Each time water spills over the dam, an opportunity to
generate electric power is lost. In the picture above Bruce is
looking at the Burton Dam computer. This older system does not
give the operator as much detail in monitoring or as much control
over the generating unit. This older system will sound a warning
if the unit needs some sort of attention. However, unlike the
new system, a worker must manually go up to the dam and find the
problem and make the necessary adjustments. Many of these adjustments
to the units controlled by the new system can be handled from
this control room. Burton should be connected to the new computer
system in the not too distant future.
Each generating unit has its own transformer
located on the floor above it in the powerhouse. These transformers
increase the voltage from 6600 to 115,000. This increased voltage
is necessary in order for the electricity to travel along the
power grid and reach the locations where it is to be used. Southern
Company has sold power to locations as far away as California.
Before this high voltage power can be used, it must pass through
another transformer which reduces the voltage to a usable level.
An example of this is a transformer outside a residence that would
reduce the voltage to 220.
The picture above shows the circuits
and power lines in the high tension room. The electrical voltage
has been transformed to 115,000 volts and is leaving the powerhouse.
Its destination is the Southern Company power grid.
The railway is not the only way out
of the gorge, but it may be the best way.
Special Thanks to Donna Westmoreland
for her assistance with the photography.
THE MATHEMATICS
The three primary jobs
related to the mathematics involved in generating hydro-electric
power are the plant operators, plant maintenance personnel, and
the plant engineers.
Plant Operator
One of the duties of
the plant operator is to monitor the water levels of the lakes.
The goal is to maximize the power generating potential of the
water in all the lakes in the North Georgia Hydro Group. Therefore,
lake levels must be closely watched so that water is not lost
over the dams. Keeping an eye on the weather plays a significant
role. If a large storm is approaching, lake level must be drawn
down in order to make room for the extra storm water. Drawing
down lake levels means opening the generating unit gates and generating
hydro-electrical power. Since water used to generate power in
a plant upstream is expelled into the lakes downstream, each time
the gates are opened in a generating unit it sets off a chain
reaction in all of the lakes and generators downstream because
of the need to maintain proper lake levels.
The plant operator
has a schedule of power generation that he must follow. This schedule
is made by the engineers in the Atlanta office and reflects the
power needs that must be generated and made available to the many
customers serviced by the Southern Company electrical grid. The
operator must manage the system so it meets peek power demands
and at the same time keeps lake levels that are appropriate for
the recreational needs on all the lakes without losing any excess
water over the dam.
Other than the data
collection and summation skills use to fill out the daily log
sheets, the plant operator may not notice the mathematics involved
in doing his day to day job. He must have proficiency in basic
mathematical concepts in order to understand electricity, hydro-electrical
power generation, and the ability to think critically and solve
problems that involve logical thinking.
In addition to having
a high school diploma, each operator must have enough mathematical
knowledge to pass a pre-employment test, an operations test, and
a plant operators test. Many of these operators have passed the
tests and have experience working as operators in power plants
dealing with mechanical, electrical, and steam generation.
Maintenance Personnel
In order to maintain a generating unit
properly, it must be almost completely taken apart. When the maintenance
personnel re-assemble the unit, every part must be aligned within
1/1000 of an inch. They must be able to read, understand, and
use instruments such as micrometers. They must also be able to
read dial indicators like those found on a metal lathe. Calculations
involving angles, measurements, and problem solving may range
from very simple arithmetic and geometry to more complicated geometry
and trigonometry.
Consider the following example of a
project that maintenance personnel may encounter. In order to
connect two water pipes, a flange must be constructed around the
end of each pipe. The two pipes are then bolted together through
holes in each flange. If ten equally spaced bolts are to be used,
where should the holes in the flange be constructed? One solution
is to divide the circle (360 degrees) into ten 36 degree angles.
If the bolt holes are constructed on the rays of the 36 degree
angles, then they will be equally spaced.
Plant Engineer
The plant engineer must have a greater
degree of mathematical knowledge than either the plant operator
or the maintenance personnel. A college degree in engineering
requires mathematics beyond the level of calculus. Furthermore,
any major changes or additions to the plant or its operation will
be directed by the engineers. The on going project of computerizing
the plant operations so that everything can be controlled from
the Tallulah Falls control room is an example of a modification
designed and directed by the plant engineers.
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