It is the study of finding the voltage, current, and power factor or reacting power at different points in power system installed.

Load study is strongly recommended in a system which is in operation for future enhancement because to make the system work perfectly and satisfy the demand at user end it is necessary to know about the effects of interconnection with other power systems, and of adding new loads and the addition of new generation system.

Long-term calculation are parity much tedious when specially when they belongs to complex systems. To avoid this difficulty there is a solution available in the world of engineering and technology. This is solution is an ac calculating board. It is best method to make a load study to find the effects of possible changes.

An ac calculating board is small scale power similar to original power system on which load study is being applied. It is always single phase system either original system is single phase or poly phase. It consist of many ac voltage sources which are equal to the voltages of original system, which could adjusted in magnitude and phase and also consist of number of resistance and current elements which are usually connected by plugging arrangements to present the actual system. These accessories are connected in equivalent circuits of its components parts. All values of a power system are scaled down to convenient size. Measurements made on the calculating can be easily converted by multiplying factors, to the value would exists on the real network.