Electrical Distribution Systems

TN

• 3-Phase, 4-Wire 400Y/230 V
• used in Europe and others

IT

• 3-Phase, 3-Wire 230 V Wye (No neutral)
• used in Norway

Three Phase Three Wire Delta

• used to provide power for three-phase motor loads in industry, and utility power distribution systems
• voltage typical 240, 400, 480, 600 and higher

277/480V Three Phase Four Wire Wye

• used in larger U.S. facilities with voltage 277/480. 277 volt is used as single phase for lighting and 480 volt is used for larger loads like HVAC systems
• in western Canada 347/600V is commonly used

120/240V Three Phase Four Wire Delta

• used in older manufacturing facilities with mostly three-phase motor loads and some 120 volt single-phase lighting and plug loads

120/240V Single Phase Three Wire

• grounded neutral system
• known as the Edison system, split-phase or center-tapped neutral
• common as residential service in North America

120/208V Three Phase Four Wire Wye

• grounded neutral system
• the most common commercial building electric service in North America