Center for the Study of Energy Markets

Power transfer distribution factors depend on the operating point and topology of an electric power system. However, it is known empirically that, for a fixed topology, the power transfer distribution factors are relatively insensitive to the operating point. We demonstrate this result theoretically for lossless systems in two ways: as an exact result for a system having "series-parallel" topology and a single point of injection and a single point of withdrawal and also as an approximate result for systems of arbitrary topology but having reactive compensation sufficient to keep voltages constant at all busses. To the extent that losses are small, the results apply also for more realistic systems with losses. We also analyze two other distribution factors that more closely relate to thermal and steady-state stability constraints.