Electrical Power Electrical Power Distribution in Distribution in
AmericaAmerica
49.9 % Coal49.9 % Coal
20.4% Nuclear20.4% Nuclear
20.3% Natural Gas20.3% Natural Gas
6% Hydro Electric6% Hydro Electric
3.4% Other3.4% Other
http://www.eia.doe.gov/emeu/mer/pdf/pages/sec7_4.pdf
Power Plant Generation
Turbines Output 11KV to
22KV
Generated Power Distribution Power Plant
Turbine Output Voltage Transformed to Higher Voltage
155,000 volts to 765,000 Volts
Higher voltage, lower current = less line loss
End User High Distribution
Voltage Transformed Down
Common Commercial Substation Voltage 12,000 Volts
Residential 7,200 Volts
Commercial End User Transformed From 12,000 Volts, 3
Phase 480/277 Volts Three Phase 208/120 Volts Three Phase
480/277 Volt Rules of Thumb
Phase Conductors Marked BrownBrown, , OrangeOrange, , YellowYellow Neutral – White Ground – Green
Voltage reading between phases (BrownBrown to to OrangeOrange, , YellowYellow to Orange to Orange, or , or YellowYellow to to BrownBrown)
480 volts
Voltage reading phase to neutral (BrownBrown to White, to White, OrangeOrange to White, or to White, or YellowYellow to to WhiteWhite)
277 volts
208/120 Volt Rules of Thumb Phase Conductors
Marked Black, Red, Blue White - Neutral Green – Ground
Voltage Reading Between Phases (Black to Red, or Red to Blue or Black to Blue) 208 Volts
Voltage Reading Phase to Neutral (Black to White, Red to White, Blue to White) 120 Volts
Residential End User
Transformed From 7,200 Volts 240/120 Volts Single Phase
Residential Single Phase 3 Wire’s coming into
your home
Black and Red Wires are Hot
1 White is Neutral
Voltage between the two hot wires (Black to Red)
240 volts
Voltage between hot and neutral (Either the Black to White or the Red to White)
120 volts