A Modified Voltage SAG Duration for Power Quality Diagnosis

Abstract This paper newly defines a voltage sag duration considering the voltage tolerance characteristics of individual electrical device for power quality (PQ) diagnosis. In PQ diagnosis, the magnitude and the duration of voltage sag are important parameters that characterize the voltage sag event. The conventional sag characterizing method has the possibility to overestimate the voltage sag. Furthermore it cannot take the characteristics of each device into account. The proposed method utilizes the minimum voltage of voltage tolerance curve. The voltage sag profile is approximated and the modified duration is newly defined considering the voltage tolerance characteristics. The proposed method is applied to the non-rectangular sag originated from induction motor starting and proved to be effective for PQ diagnosis. The modified voltage sag duration can be applied to stochastic analysis of PQ diagnosis and will give more realistic understanding to the customers.