Types of power distribution !!

There are broadly two form in which electricity can be generated, Direct Current and Alternating Current.

Direct Current: Direct current is the type of electricity supplied by a battery. One terminal is positively charged, the other negatively charged and electricity flows from one to the other, always in the same direction. However, while it is simple to make and control, DC does not travel well over long distances; it gets used up by the resistance in the transmission lines and is gone before it gets to where it is needed.

Alternating Current: Alternating current is also has a positive and a negative terminal but the polarity and the direction of flow alternates many times per second. Electricity alternates polarity 120 times per second or 60 full cycles per second. in America. i.e. 60 Hz AC can travel well over long distances but in the Asia, alternates polarity will be 220 times per second, or 50 full cycles per second, i. e. 50/60 Hz AC can travel well over the long distance, so it the choice for power distribution lines.

There is no difference between Amps or Volts between AC and DC. Some devices can only operate on one type of system or the other, but otherwise a volt is a volt.

Power is usually generated at a distance from where it is used. It is supplied as 3-Phase power at very high voltages. This allows many kilowatts to flow through fairly small conductors because amperage is effectively small. There are 3 hots, each 120/220 degrees out of phase with the next when their sine waves are plotted against each other, hence the term '3 phase'. There is no neutral. This configuration is called Delta, and is the same type use to run 3 phase motors.

The power level is brought down through a series of substations. At each step transformers reduce the voltage and increase the amperage until it reaches the line transformers outside the building. At that point, the Delta service is converted to a Wye service and is brought into the building at the 'service entrance'.

The Wye service has the same three hot legs, plus an electrical neutral created at the transformer. By this time in either Wye or Delta, the line voltage has been brought down to where each hot terminal is 120/220 Volts above earth potential, called 'ground' and in the case of a Wye service, each hot is also 120/220 V above the Neutral as well. However, due to the geometry of the hot phases, there is a difference of between any two hots in either type of 3 phase system.