An improved fault analysis method based on bus-voltage thresholds determination for distribution networks with distributed generators

Integration of distributed generators (DGs) into a distribution network (DN) can impact on the reliability operation and stability of protection systems. Depending on DG types, their installed locations, and operation states, fault current values in the distribution network can be significantly changed such that protective devices can inaccurately operate. Traditional fault analysis methods have not considered the presence of distributed generators and their operation characteristics, bidirectional power flows and change in bus-voltage values in the DN. Therefore, improvement of fault current calculation methods is necessary to fast, automatically and accurately determine fault current values in the DN with distributed generators. Hence, this paper develops an improved fault analysis method based on bus-voltage thresholds determination for distribution networks with DGs. The bus-voltage thresholds can be evaluated by determining load power confidence intervals (LPCI), and fault current thresholds will be then calculated in the DN with DGs. Based on a developed LPCI calculation tool and E-terra distribution software, achieved simulation results have validated the effectiveness of fault analysis method based on bus-voltage thresholds for distribution networks in case of considering types, locations and operation states of various distributed generators.