Power Systems

Last edited: Monday, June 1st, 2015

Before Power Distribution

• Technology developed 50-100 years before power distribution to the public:• Batteries• Arc Lights• Incandescent Lights• Electric Motors (vacuum pump)

DC vs. AC

• Direct current (DC)– DC machines– Batteries– Fuel cells– Photovoltaic

• Alternating current (AC)– AC machines– Power electronic converters– 60 Hertz in the US

Brush Electric Company

• HVDC distribution that transmitted over longer distances to one customer• Niagara Falls to Buffalo

• Simple distribution system that could only power arc lights

Edison Electric Company

• Low voltage direct current system• Better lightbulb• Safer• Short range use• Powered Small DC motors

• Features added• Electric meter• Distribution System

Westinghouse Electric Company

• Low and High Voltage Alternating Current system• Long distance transmission• Able to change voltage• Compatible with Edison Bulb• Developed Westinghouse Bulb• Own patent for AC Motor

Grid Expansion

• Grid distribution networks expanded until around 1915.• The smaller grids slowly integrated into one system by

connecting the distribution grids by transmission lines.•More transmission lines were added during the 1930s as part

of the Depression projects and rural areas received electricity• By the 1960’s the gird was largely intact and upgrades

occurred to make the lines more reliable.

Major Power Grid Components

• Generation

• Transmission– 115 kVolts 765 kVolts

– Networked

• Distribution– 4 kVolts to 69 kVolts

– Radial

• Load

Major Power Grid Components

All power systems have three major components: Generation, Transmission/Distribution, and Load.

Generation: Creates electric power.

Transmission/Distribution: Transmits electric power from generation to load.

Load: Consumes electric power.

Power in = Power Out

The Electric Grid Model

Interconnections

AC Transmission Grid

DC Transmission Components

Transmission & Distribution

Transmission Distributionnetworked connections radial connections

power can be supplied from multiple sources

power moves in one direction only

typically higher voltages, above 100 kV

typically lower voltages, below 100 kV

mostly overhead, with some underground in urban areas

most new construction is underground, especially in

suburban and urban locationsoften source of large-scale

blackoutsthe source of most blackouts,

but these are local

Synchronism

16

Since most generation is from synchronous machines, the interconnected power system swings together.

North American Control Areas