The power grid
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The Power Grid. ELEC 403 The Citadel Mark McKinney. The Power Grid. Number one invention of the 20 th century is electrification US has one of the most extensive and reliable networks in the world. The Power Grid.

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The Power Grid

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The power grid

The Power Grid

ELEC 403

The Citadel

Mark McKinney


The power grid1

The Power Grid

  • Number one invention of the 20th century is electrification

  • US has one of the most extensive and reliable networks in the world


The power grid2

The Power Grid

  • US and Canada are divided into eight large regions (RROs – Regional Reliability Organizations) overseen by the North American Electric Reliability Council (NERC)

  • South Carolina is in SERC

Source: NERC


The power grid

SERC Transmission Mileage

(161kV and above)

SERC

  • Comprised of about 50 member companies, co-ops, and municipalities that supply energy within the region

  • Covers an area of approximately 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


The power grid

SERC

  • Comprised of about 50 member companies, co-ops, and municipalities that supply energy within the region

  • Covers an area of approximately 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


Us energy usage

US Energy Usage

Source: US Energy Information Administration


Power in sc

Power in SC

  • South Carolina’s four nuclear power plants supply about half of the State’s electricity demand.

  • South Carolina receives most of its coal from Kentucky.

  • Industry is the State’s largest energy-consuming sector, accounting for roughly two-fifths of total energy consumption.

Source: US Energy Information Administration


Power in sc1

Power in SC

  • If licensing and construction go as planned, two new nuclear reactors could come online in South Carolina by 2016.

  • Per capita electricity use in South Carolina is higher than the nationwide average due to high air-conditioning demand during hot summer months and the widespread use of electricity for home heating during generally mild winter months.

Source: US Energy Information Administration


The us power system

The US Power System

  • The 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 for “transmission”


The us power system1

The US Power System

  • The Transmission Substation

  • Voltage stepped-up to 150-500kV

  • Allows for transmissions up to 300 miles.


The us power system2

The US Power System

  • Transmission 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


Transmission lines

Transmission Lines

Aluminum has replaced copper lines because they have lower cost and are lighter weight.

A shield wire is connected directly to the top of transmission line towers to protect the main conductors from a direct lightning strike.

Transmission lines are connected to the towers by porcelain insulators.

Source: American Transmission Company


Transmission line structures

Transmission Line Structures

Designs of transmission lines vary greatly to meet various needs

  • Electrical Properties

    • Electrical Capacity (I)

    • Transmission Distance (V)

    • Efficiency (R, L, & C)

  • Aesthetics

    • Wood or Steel Construction

    • Physical Size

  • Environmental Impact


Transmission line structures1

Transmission Line Structures

Designs of transmission lines vary greatly to meet various needs

  • Accessibility

    • Constructability

    • Maintainability

  • Zoning and land-use

  • Right-of-way/Easement

    • Width and height restrictions

    • Determine voltage and height of tower


Transmission line structures2

Transmission Line Structures

Double-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 to do this.

Source: American Transmission Company


Transmission line structures3

Transmission Line Structures

Double-circuit, 138-kilovolt line build on galvanized steel poles.

This type of design is often used when the line will carry heavy electric loads. Higher voltage lines require taller poles-sometime 100 feet or more.

Source: American Transmission Company


Transmission line structures4

Transmission Line Structures

138-kilovolt single-circuit line on weathering steel.

This type of maintenance-free structure will weather (rust) over time to give the appearance of wood and is generally used in wooded areas.

Source: American Transmission Company


Transmission line structures5

Transmission Line Structures

H-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.

Source: American Transmission Company


Transmission line structures6

Transmission Line Structures

138-kilovolt steel H-frame.

Require less height, but wider right-of way.

Source: American Transmission Company


Transmission line structures7

Transmission Line Structures

345-kilovolt, double-circuit on single poles.

Higher voltage lines require taller poles and wider rights-of-way.

Source: American Transmission Company


The power substation

The Power Substation

  • Power Substation

  • Steps-down the HV for the “distribution” network

  • Voltages <100kV


The power substation1

The Power Substation

  • Power Substation

Switch Tower and Main Transformer

Distribution Bus


The distribution network

Smaller, low-voltage poles

Simpler designs – usually wooden Ts

Typically 7.2kV

The Distribution Network


What s on the poles

Capacitor banks

What’s on the poles?


What s on the poles1

Reclosers

What’s on the poles?


What s on the poles2

Transformers

What’s on the poles?


At your house

Transformer

Tap off of one (occasionally two) phase

At your house


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