On-Line Monitoring of Sag in Overhead Transmission Lines with Leveled Spans

A method for real time monitoring of overhead transmission line sags has been proposed. Mechanical state estimation is used to determine the sag value of each span of the transmission line using real time data. Use of separate tension sensors for critical spans enhances the sag estimation process. The estimated sag values can be used to calculate the clearance values to check for compliance with the national electric safety code (NESC).