A load flow analysis is undertaken during the design stage of an electrical distribution system, or during operation if problems are encountered. Load flow analysis refers to the problem of determining the voltages at various points in the system, and the power flow in the lines (cables). Due to the large number of calculations required to arrive at a solution, load-flow is typically analyzed with a computer. 

Voltage:

The voltages at the main busses (power distribution centres and motor control centres) are calculated. Cable sizes may then be optimized, and power factor compensation applied, to ensure voltages are within an acceptable range – approximately 95 to 105% of nominal.

Based on the voltage calculations, settings for transformer tap changers can be recommended. A control strategy can be developed for automatic tap changers. 

Power:

Real power (kW) and reactive power (kVAR) flows through the lines of the system are calculated.

The power factor at the customer’s connection to the utility system can be corrected to a level required by the utility. As the utility company will charge a premium for a power factor outside of a certain range in most cases, there may be a strong economic incentive to adjust the customer’s power factor by applying power factor correction.

Power losses in lines can be calculated and based on these, the line size may be adjusted to minimize losses.