Voltage-drop calculations and power-flow studies for rural electric distribution lines

The history of distribution system voltage-drop and loss calculation from paper-and-pencil methods to full three-phase power flow calculations using the digital computer is examined. The methods discussed include an approach that allows unbalanced operation (such as an open-wye line) to be analyzed accurately. It is suggested that intelligent use of the models will entail using the more detailed models only if necessary, thereby avoiding unnecessary computational expense. It is much more important to use a reasonable value for the load power factor than to account exactly for every small unbalance in the line impedances. Recommendations to aid the practicing engineer in the choice of the best analytical tools are offered