intro to power

8/6/2019 Intro to Power

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The Power Transmission SystemThe Power Transmission System


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The Power GridThe Power GridNumber one invention of

the 20th century is

electrificationUS has one of the most

extensive and reliable

networks in the world


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The Power GridThe Power GridUS and Canada aredivided into eight largeregions (RROs

Regional ReliabilityOrganizations) overseenby the North AmericanElectric Reliability Council(NERC)

South Carolina is inSERCSource: NERC


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SERCSERCSERC Transmission Mileage

(161kV and above)

0

5,000

10,000

15,000

20,000

25,000

161kV 230kV 345kV 500kV

Comprised of about 50

member companies, co-ops,

and municipalities that supply

energy within the region

Covers an area ofapproximately 560,000

square miles in sixteen states

Supplies about

1,000,000GWh of energy

annually Dominated (like the US) by

coal and nuclear generation

Source: SERC Information Study, July 2006


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SERCSERC Comprised of aboutmember companies co ops

and municipalities that supply

energy within the region

Covers an area ofapproximately

square miles in sixteen states

Supplies about

GWh of energy

annually Dominated (li e the US) by

coal and nuclear generation

Nuclear

%

Dual Fuel (Gas/Oil)%

Gas

% Oil

%

Net Internal

Purchases9%

Coal

8%

Pumped Storage

%

Hydro

%

Source: SERC Information Study, July 2006


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US Energy

Usage

US Energy

Usage

Source: US Energy Information Administration


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Power in SCPower in SC South Carolinas four nuclear power

plants supply about half of theStates electricity demand.

South Carolina receives most of itscoal from Kentucky.

Industry is the States largestenergy-consuming sector,

accounting for roughly two-fifths oftotal energy consumption.



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Power in SCPower in SC If licensing and construction go as

planned, four new nuclear reactorscould come online in South Carolinaby 2020.

Per capita electricity use in SouthCarolina is higher than thenationwide average due to high air-conditioning demand during hotsummer months and the widespreaduse of electricity for home heatingduring generally mild winter months.



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TheU

S Power SystemTheU

S Power SystemThe Generating Station Can be nuclear, coal, etc

Usually a steam turbine

Generates 3-phase AC power

Output usually in the 10-

30kV range

Voltage must be increased to

high voltage fortransmission


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TheU

S Power SystemTheU

S Power SystemThe Transmission Substation Voltage stepped-up to

150-500kV

Allows for transmissions up

to 300 miles.


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TheU

S Power SystemTheU

S Power SystemTransmission Lines The transmission phase

covers long distances at high

voltages

Towers are BIG

Overseen by NERC

Connect power plant to

localities

Also connect the various

companies and even regions


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Transmission LinesTransmission LinesAluminum has replaced copper linesbecause they have lower cost and arelighter weight.

A shield wire is connected directly tothe top of transmission line towers to

protect the main conductors from adirect lightning strike.

Transmission lines are connected tothe towers by porcelain insulators.

Source: American Transmission Company


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Transmission Line StructuresTransmission Line StructuresElectrical Properties

Electrical Capacity (I)

Transmission Distance (V)

Efficiency (R, L, & C)

Aesthetics

Wood or Steel Construction

Physical Size

Environmental Impact

Designs of transmission lines vary greatly to meet various needs


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Transmission Line StructuresTransmission Line StructuresAccessibility

Constructability

Maintainability

Zoning and land-use

Right-of-way/Easement

Width and height restrictions

Determine voltage

and height of tower

Designs of transmission lines vary greatly to meet various needs


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Transmission Line StructuresTransmission Line StructuresDouble-circuit, 138-kilovolt

transmission line built on wood

structures.

Local electric distribution lines,

cable and telephone lines are

sometimes carried on the same

structures to make efficient use of

space. Taller poles are needed todo this.



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Transmission Line StructuresTransmission Line StructuresDouble-circuit, 138-kilovolt line

build on galvanized steel poles.

This type of design is often usedwhen the line will carry heavy

electric loads. Higher voltage

lines require taller poles-

sometime 100 feet or more.



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Transmission Line StructuresTransmission Line Structures138-kilovolt single-circuit line on

weathering steel.

This type of maintenance-freestructure will weather (rust) over

time to give the appearance of

wood and is generally used in

wooded areas.



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Transmission Line StructuresTransmission Line StructuresH-frame wood structure.

This type of design allows for

shorter spans (the distance

between structures.) In general

the height of the structures is less

than single pole structures.



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Transmission Line StructuresTransmission Line Structures138-kilovolt steel H-frame.

Require less height, but wider

right-of way.



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Transmission Line StructuresTransmission Line Structures345-kilovolt, double-circuit on

single poles.

Higher voltage lines require taller

poles and wider rights-of-way.



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The Power SubstationThe Power SubstationPower Substation Steps-down the HV for the

distribution network

Voltages


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The Power SubstationThe Power SubstationPower SubstationSwitch Tower and Main Transformer

Distribution Bus


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The Distribution NetworkThe Distribution NetworkSmaller, low-voltage

poles

Simpler designs usuallywooden Ts

Typically 7.2kV


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Whats on the poles?

Whats on the poles?

Capacitor banks


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Whats on the poles?

Whats on the poles?

Reclosers


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Whats on the poles?

Whats on the poles?

Transformers


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At your house

At your house

Transformer

Tap off of one

(occasionally two) phase


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The future The Smart GridThe future The Smart Grid

Central systemCentral systemDistributed systemDistributed system

Additional Sources Efficient Loads Recapture DevicesAdditional Sources Efficient Loads Recapture Devices

Combined Heat and Power recapture lost heat

Microturbine use exhaust

for generation

Motorformer motorspecialized to provide reactive power

AdditionalSources

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