Tracing active and reactive power between generators and loads using real and imaginary currents

In a competitive environment, usage allocation questions must be answered clearly and unequivocally. To help answer such questions, this paper proposes a method for determining how much of the active and reactive power output of each generator is contributed by each load. This method takes as its starting point a solved power flow solution. All power injections are translated into real and imaginary currents to avoid the problems arising from the nonlinear coupling between active and reactive power flows caused by losses. The method then traces these currents to determine how much current each source supplies to each sink. These current contributions can then be translated into contributions to the active and reactive power output of the generators. It is also shown that the global contribution of a load can be decomposed into contributions from its active and reactive parts. This decomposition is reasonably accurate for the reactive power generation. To determine the contributions to active power generation, the previously-described method based on the active power flows is recommended