Load-Flow Studies

The load or power flow study is a steady state analysis of the system capability to supply the connected load. The study will provide:
A list of real power and reactive power flow in the system, with the flow direction in each line or branch is provided. The losses in that line or branch, together with all the system losses are also supplied.
The bus voltage magnitude and angle calculated at each bus or node in the system.
All results are based on either the measured load or the calculated design loads at each bus, the system topography and the system elements data.

The results will be used to determine:
The optimum taps settings for power transformers.
The need and justification of power factor correction capacitors (shunt capacitors). These capacitors will supply the reactive power needed for the load and lower the overall system KW losses when connected near or at the load.

The possible overloading of the system transformers, generators and tie circuits during an emergency operating conditions existed.

The instantaneous effect on the system voltage whenever a suddenly large loads such as the starting of large motor load or starting of arc furnaces is applied. The effect of starting large motor loads on the system can be calculated with the load flow study performed several times for a predetermined time during which the motor reach full speed. The motor starting current and power factor will be changed during the starting to calculate the effect on the system voltage during each instant until the motor reach its full speed.

Several load flows are required for each system condition ( normal , abnormal, emergency generators on, tie open, and whatever system conditions that have to be considered for the study.

The load flow study is a pre- requisite to stability study. The load flow study is used as a part of the motor starting study The load flow study can be used as a pre- requisite to the SC study, but generally SC studies (for most systems) do not consider the system loading effect on the SC.