Sensitivity of transfer capability margins with a fast formula

Bulk power transfers in electric power systems are limited by transmission network security. Transfer capability measures the maximum power transfer permissible under certain assumptions. Once a transfer capability has been computed for one set of assumptions, it is useful to quickly estimate the effect on the transfer capability of modifying those assumptions. This paper presents a computationally efficient formula for the first order sensitivity of the transfer capability with respect to the variation of any parameters. The sensitivity formula is very fast to evaluate. The approach is consistent with the current industrial practice of using de load now models and significantly generalizes that practice to more detailed ac power system models that include voltage and reactive power limits. The computation is illustrated and tested on a 3357 bus power system.