Supply voltage

[Shiju]

Why is that supply voltages have been standardised to 230/240/250V...ALso in America we find it is different in different regions, 120/240/277...what are the advantages of this?Also does the frequency play role in our household equipments like tv,refrigerator...

 

[mjevans]

You should find the answers to few of your questions here.

http://users.pandora.be/worldstandards/electricity.htm