Tutorial onPower Distribution
Circuits
G. Heydt
Arizona State University
March, 2003
What is power distribution?Power systems are made up of:• Generation• Transmission• Distribution
Generation systems are the large generating units that produce AC voltages at high power levels. Transmission systems are long distance, very high power level systems to transmit power from city to city. Distribution systems are local, lower power systems that take power from the intercity grid and bring this to residences, commercial customers, and industrials
Typical numbers
Generation Transmis-sion
Distribution
Typicalvoltages
35 kV 345 kV 15 kV
Typicalpower
800 MW 800 MW 1 MW
Typical size In a powerplant
Inter-city,200 km
Local inneighbor-
hood, 5 km
Typical configurations
Transmission systems are NETWORKED usually. That is there are many loads and many sources, and many lines that join these points in a mesh, networked fashion.
FLAGSTAFF
PRESCOTT
PHOENIX
TEMPE
NOGALES
WINSLOW
HOLBROOK
Typical configurationsTransmission systems are networked so that power can be delivered between load centers by several routes. If a line is removed from service, power can be rerouted. Like power delivered to Nogales from Flagstaff by two different routes.
FLAGSTAFF
PRESCOTT
PHOENIX
TEMPE
NOGALES
WINSLOW
HOLBROOK
Distribution systems
Distribution system configuration is usually different -- rather than being networked, distributuin systems are usually RADIAL. That means lines go from A to B to C to D to ...
RURAL RD PRICE RD MESA-W MESA-C MAIN ST
Distribution systems
Power can only flow in one direction in the radial system
RURAL RD PRICE RD MESA-W MESA-C MAIN ST
Distribution systems
Why is this configuration used?• Safety (only one source direction - when it
is interrupted, the line is dead)• Cost -- it is cheaper• Easy to locate problems
RURAL RD PRICE RD MESA-W MESA-C MAIN ST
But there are advantages of reliability of networked systems - provided cost, safety, control, and maintenance issues can be resolved.
A TYPICAL RADIAL
DISTRIBUTION SYSTEM
Research and study areas• The reliability vs cost of networked
systems versus radial systems
• Use of networked systems (they do this in big cities like Chicago and New York)
• Control of power in a networked distribution system
Deployment of distribution components,multiple feeds, and over-capacity
Cost
INVESTMENT COST
COST OF SERVICEINTERRUPTIONS ANDLOSS OF PRODUCTIVITY
TOTAL COST
Directed reading
Some easy to read texts on distribution engineering:
Acknowledgements
• To my colleagues and students who are working on the project
• To Dr. Momoh at the NSF
• To the staff at ONR for their input
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