Development and Investigation of a Proposed Voltage Sag Index

A proposed voltage sag index based on power flow equations is developed and investigated in this paper. The index supervises the power quality of a system, through calculating the voltage sag profile caused by an increase in reactive demand due to induction motor starting. Mathematical equations representing the load angle of the system are also derived. The accuracy of the index is investigated for a range of load, transmission, and distribution line X/R ratio values as well as various motor loading levels. Results demonstrate the effectiveness and applicability of the proposed index.