The Impact of X/R ratio on Voltage Stability in a Distribution Network Penetrated by Wind Farms

Existing technologies used for voltage regulation through reactive power control are mainly based on the reactance of the line while the line resistance is ignored. Hence, these solutions are appropriate for transmission networks where X/R ratio is high. However, this assumption does not hold for distribution systems as the value of line reactance is low, resulting in low X/R ratios. This paper investigates the effect of X/R ratio on reactive power requirements, voltage profile and step-voltage variation at the Point of Common Coupling (PCC) of a wind farm connected to a distribution system. The test distribution system has been modelled using different IEEE standard distribution systems. The results show that an increase in the X/R ratio increases the reactive power requirement and lowers the voltage at the PCC. However, lower X/R ratios increase the step-voltage variations as a function of wind power and adversely impact the power quality of the system.