Investigations on transmission system performance analysis with voltage variation

Usually, the transmission line models, assume sending-and receiving-end voltages as constant, practically, which becomes difficult to maintain, due to its stochastic nature. Thus, for reliable and secure operation of the power system, their performance analysis becomes important. Availability of time-synchronized voltage measurements, at both ends of the transmission lines, allows their more accurate performance analysis. This paper utilizes circle diagrams, derived from ABCD parameter, as a graphical technique for analyzing the power flow variation, i.e., active, reactive, and apparent power at different voltage levels, at sending- and receiving-ends, both, of the transmission lines. Further, indices are proposed to evaluate the power flow variation with voltage. Also, resorting a third dimension of voltage to the circle diagrams, another useful representation of the power-chart transformation as projective relation is proposed. This method, being graphical, offers advantages of ease in analyzing the power flow on transmission lines to the operator, determining the power flow limits, etc. Also, from the smart grids perspective, these relationships help in maintaining secure power flow in the transmission network.