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.


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 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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