Overview of voltage sag profile estimation

Voltage sags are considered important because they may cause equipment to malfunction and/or interrupt industrial processes and commerce. There is a need for voltage sag profile estimation, because voltage monitoring equipment may prove costly for utilities. This paper provides a review of existing work on voltage sag profile estimation. The methods under sag profile estimation were classified as: (1) model- and (2) measurement-based. This classification is useful in selecting the sag profile estimation method based on the information available. The first group consists of the method of fault positions, the method of critical distances, and the bus impedance matrix and voltage sags matrix method while the second group consists of normalized voltage profile curve-fitting, disturbance circuit, Kalman filter, estimation through fault location and identification, voltage sensitivity method, and transient state estimation.