What is Power Wheeling ?

Power Wheeling is the transfer of power from the point of generation by a power producer using the transmission networks which do not belong to him.

Power wheeling is used by owners of large power plants which do not have their own transmission networks.  These producers usually pay a sum to the utility or company which owns the power transmission network. 
The charges for using the network may vary with the time of day.  As the congestion on the networks is higher during the daytime and less during the off-peak hours, the charges are higher during the peak hours and lower during the off-peak hours.

Hence, it is essential to measure the power and the time of the day in which it was transferred.  Hence, there are special time-of-day energy meters to record the time as well as the amount of power transferred.