Jake Perez

Student ID 1514624

ELMT 1391.2001 – Special Topics in ElectroMechanical Technology

Senior Essay – “From Wind to 120VAC in Austin, TX – The Process”

Electricity has been around for hundreds of years. Through

out the years we have discovered many ways to harness

electricity. There is coal, solar, nuclear, geothermal, steam,

gas, oil, and finally wind. This essay will be about how

Austin harnesses the wind to generate electricity for every

day use.

Before any power can be generated, the wind turbine must

first detect a few things. The speed, direction and

consistency of the wind must be at the right conditions for

the turbine to turn on. This is done by using an anemometer.

An Anemometer is a device used for measuring wind speed. The

Anemometer is hooked up to a computer with a fiber optic cable

inside the nacelle which then tells it the direction its

blowing from and how consistent it is. Along with other

important information. Once all requirements are met the

turbine starts winding up.

After it winds up, the nacelle rotates to the wind with the

help of yaw motors located directly below structure. Once the

turbine is facing the wind, the blades will then pitch to a 45

degree angle so it can begin to harness the wind. These blades

are similar to airplane wings. Air passes on both sides of the

blade, because of the shape of the blade. It causes air

pressure to become uneven. The pressure is higher on one side

and lower on the other. The uneven pressure causes the blades

to spin around the hub of the turbine. The blades are

connected to a rotor which is connected to a low-speed shaft

inside the hub. Which will take us to the next paragraph.

The low-speed shaft spins at about 30-60 rotations per-

minute. (RPM) The shaft is connected to a gear box which

increases the rotation speeds to 1,000-1800 rpm. The gear box

is one of the heaviest part of the turbine and also the a very

expensive piece of equipment to replace. From the gear box

you have the High-speed shaft that is connected to the

generator.

The most common generator in a wind turbine is a Induction

Generator. Induction generators produce electrical AC power

when their shaft is rotated faster than the synchronous

frequency of the equivalent induction motor. Induction

generators are mechanically and electrically simpler than

other generators types. Induction generators require an

external supply to produce a rotating magnetic flux. The

external supply can be supplied from either the electrical

grid or from the generator itself once it starts producing

power. You can also use a capacitor bank to start the

generator as well. Once generated the power travels down

tower. The voltages the generator creates can vary from 600 V

to 4000 V.

Each operating wind turbine has a three-phase pad mounted

transformer at the base of each wind turbine. The Three-phase

pad mounted transformers job is to increase the voltage the

generator makes. This voltage can but up to 400,00 volts. From

the pad mounted transformer it is sent to a switch station

that is connected to all the wind turbines on that particular

farm. From the transformer it is sent to a transmission

substation where the power will be distributed on the grid.

Once power is on the grid it is sent across the state by

high voltage transmission lines. These transmission lines are

made of copper or aluminum because they have a low resistance

to electricity. Higher resistance means the wire will get

warmer. Because the wires heat up some of the energy is lost

in transit. There are 450,00 miles of high-voltage power

lines and 160,00 miles of over head transmission lines in the

United States connecting electrical power plants to homes and

businesses.

From the high voltage transmission lines power is then sent

to a step down transmission substation. A step down

transmission substation are located at switching points on the

electrical grid. They connect different parts of the grid and

is a source for distribution lines. A step down substation can

change the transmission voltage to a sub transmission voltage.

This is usually 69 kV. The sub transmission voltage lines can

then serve as a source to distribution substations.

There are two types of distribution substations. One is

above ground and the other is underground. It is called a

underground distribution substation. Its job is to change the

transmission or sub transmission voltage to a lower voltage so

it can be used at a consumer level. Distribution voltages vary

from 34,500Y/19,920 volts to 4,160Y/2400 volts. Underground

distribution substations do the same job but have a few more

parts. An underground system may consist of conduits, duct

runs, manholes, high-voltage underground cables, transformer

vault, riser and transformers. Conduits are hollow tubes

running from manhole to manhole in an distribution system.

They contain one or more ducts. These ducts can be made of

plastic, fiberglass, fiber, tile, concrete or steel. PVC and

fiberglass are most commonly used though. Duct runs are hollow

tubes running from man hole to manhole inside a conduit in an

underground system. They vary from 2 to 6 inches in diameter.

High-voltage underground cables are then ran though the ducts.

Underground cables can be constructed in many different ways,

but are usually shield cables. They are made with either a

conductor-strand shielding, insulation, metallic insulation

shielding and a sheath. These types of cables are use mostly

in circuits operating at 2400 volts or higher. Some of the

high-voltage cables are ran though a transformer vault. This

is a structure or room underground in which power

transformers, network protectors, voltage regulators, circuit

breakers, and meters are stored.

Once the high power cable has left the transformer vault,

it is ran up a utility pole to a riser. A riser is a set of

devices that connects an overhead line to a underground line.

A riser has a conduit from the ground up the utility pole

where potheads are used. Potheads are a type of insulator with

a bell or pot-like shape used to connect underground

electrical cables to overhead lines. They serve to separate

the bunched up conductors from one another in the cable, to a

much wider separation in the overhead line. It also protects

the cable end from weather related damage. These cables are

then ran from utility pole to utility pole and connected by a

hot line connector, till it has either reached a neighborhood

or a business. It is then wired to a distribution transformer

or service transformer. This last piece of equipment provides

the final voltage transformation in the electric power

distribution system. It steps down the voltage in the

distribution lines to the level used by the consumer.

Distribution transformers have ratings less than 200 kVA. From

the distribution transformer, a service wire is then connected

to the house. This is called a service drop. The service drop

is then wired a meter box outside of the residential home.

What does a meter box or electricity meter do? The most

common type of electricity meter is the electromechanical

induction watt-hour meter. Electric companies use electric

meters to measure electric energy being delivered. If energy

saving during certain periods is needed, some of the meters

may measure demand, the maximum use of power in some interval.

"Time of day" metering allows electric rates to be changed

during the day, to record usage during peak high-cost periods

and off-peak, lower-costs, periods.

After it is wired to the meter box, a NMD90 cable is then

wired to the a service box that houses the main switch. The

main switch is a mechanism allowing a residential house power

to be cut off. Power is then ran from the main switch to a

distribution panel with a 240-volt feeder cable. This device

is forming the junction of the public electricity grid and the

electric circuits of the house. The distribution panel is a

pretty important part of the power process. From this panel

the houses ground wire is wired to a ground connection in the

event of a short circuit. 2 types of current come of the the

distribution panel. There is a 120-volt circuit and a 240-volt

circuit. The 120-volt is composed of one live wire, one

neutral wire and one ground wire. This wire allows electricity

to reach small appliances or a light. The 240-volt uses two

live wires, one neutral wire and one ground wire. This allows

electricity to reach devices requiring a lot of power. Example

would be like a stove or a washer and dryer. Both of these

wires are hooked to a single and double circuit breaker. A few

other key pieces to a distribution panel are the plastic

insulator, the neutral wire, hot bus bar, ground/neutral bus

bar terminal and the ground fault circuit interrupter. The

plastic insulator is made up of noncondutive material which

prevents the hot bus bars from coming in contact with the back

of the panel. A neutral wire has no electric charge and it

allows the current to return to the distribution panel and the

grid. The hot bus bar is a conductive part of the panel into

which the breakers for each circuit are plugged into. The

ground fault circuit interrupter is a device that reduces the

risk of electric shock in a humid place in the event of an

accidental leak of current to the ground. Finally the

ground/neutral bus bar receives the current from the neutral

grounded wires of the various circuits and conducts them to

the neutral service wire and the ground connection.

From the distribution panel the 120-volt and 240-volt wires

are then ran through out the house with Romex cables to its

proper destination. Romex is the trade name for a type of

electrical conductor with non-metallic sheathing. It is

commonly used as residential branch wiring. Romex will be the

most common type of cable you will use in wiring residential

houses. Romex is used for most light and outlet circuits in

the home. It will be labeled with "12-2" or "12-3". The first

number indicates the gauge of wire. The second number

indicates the number of conductors. After the wires have been

ran to the proper destination, you can then wire them into

wall outlets. When wiring a wall outlet the neutral wire

should connect to the white or metal screw. The hot wire

should connect to the brass colored screw. The green screw is

for the ground wire. There is a tab between each of the screws

of similar color. This allows you to put the top and bottom

receptacles on separate circuits or to put one receptacle on a

switch. This tab can be removed with some if needed. Normally

you would leave the tab in place so that both outlets are

powered once you have connected to either of the screws. After

that you will have 120VAC ready to be used at the outlet.

As you can see the process in which we harness electricity

from the wind, all the way till it comes out of the electrical

socket is complicated and has many steps it has to take. In

conclusion, I hope this has cleared up and helped with

learning the process in which we get our power from wind

turbines.

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