Effect of two-circuit lines on unbalanced distribution systems

Distribution power flow analysis is one of the most important resources for proper distribution systems operation. Distribution power flow problem is very different from transmission power flow problem due to radial structure, considerable R/X ratio, load unbalance and existence of light phase. In this paper, the impedance matrix based power flow program is expanded through modelling mutual effects in two-circuit lines. Besides, the effect of this modelling on the impedance matrix based power flow results of a medium-voltage test system is investigated using MATLAB. A sensitivity analysis is done on the effect of load variation on bus voltages and feeder currents of the system. The effect of load unbalance on voltage difference among different phases of the same bus is also obviously demonstrated.