An Improved Method of Determining Incremental Loss Factors from Power System Admittances and Voltages

A method is presented for reducing the many complicated calculations of partial derivatives involved in the exact expression for incremental loss factors (that is,) needed for economic load dispatching. Calculations of the partial derivatives of voltage phase angles with respect to plant power output, which comprise the major obstacle to use of the exact expression, are avoided by digital-computer simulation of the mode of operation implied by the partial derivatives. These partial derivatives are investigated and are shown to be independent of system generation schedules and load levels. Their values may be determinied for one particular set of operating conditions and used thereafter (with the partial derivatives of total power loss with respect to voltage phase angles) to determine the most economic schedule of generation. The method gives very accurate values for the incremental loss factors for a Voltage-controlled system. For a non-voltage-controlled system, the values appear to be as accurate as those determined by B coefficients calculated by the usual tensor method.