Each of the power stations generates a definite amount of electric power. The electricity generated by all the power stations is added in the national power grid. According to the demand of different locality power sub-stations collect electricity from the national grid. Then the power sub-station delivers or distributes the electricity to the consumer level.
When in a particular area, the demand of electricity exceeds the supply or generation; the power sub-station can no longer fulfill the demand of electricity. Then the sub-station authority is forced to switch off or to disconnect the power distribution for a while in some parts of the distribution network. This is called load shedding. When the sub-station gets the supply according to its demand, then it distributes electricity in that region again.
If the load shedding takes place for a couple of hours continuously, authority load sheds circularly in different area to make load shedding tolerable at the consumer level.