Estimation of system voltage sag profile using recorded sag data

AbstractThe influence of voltage sags on electrical equipment has become a major issue because of the widespread use of voltage‐sensitive devices. In order to reduce the influence of voltage sags at each customer's site, it is necessary to identify the drop in receiving voltage due to lightning strikes on transmission lines. However, it is hard to directly measure the sag level at every load node.In this report, a new method of efficiently estimating the system voltage sag profile is proposed, based on symmetrical coordinates. In the proposed method, limited sag data recorded at each substation in the power system are used for the estimation. Since the number of recorded nodes is generally far less than the number on the transmission route, a fast method is developed to calculate only the recorded faulted voltage by applying the reciprocity theorem for the Y‐matrix. Furthermore, an effective screening process is used to select limited candidates for the faulted transmission line.Results using the IEEJ East10 standard system and actual 1700 bus system are presented, showing that the estimation accuracy is sufficiently acceptable with lower computational effort. © 2010 Wiley Periodic