Research On The On-line Monitoring Methodology Of High Voltage Overhead Transmission Line Icing

High voltage overhead transmission line is an important part of the power system. With the rapid development of China’s UHV lines, transmission line icing is threat to the safe operation of the grid. Line icing is serious in our country especially the south, which leads to large-scale power outage. In order to ensure the security and reliability of the grid, a safe and effective methodology of monitoring transmission line icing has important theoretical significance and practical engineering value.Transmission line icing will cause changes of the electrical parameters. The gravity load of the line, the sag and wire length are all increased when icing, and meantime the cross-sectional area is decreased, which finally leads to the increase of the wire resistance. Line insulator string icing increases the leakage current, resulting in line’s equivalent conductance increase for three or four orders of magnitude. Line icing reduces corona inception voltage and increases line capacitance and corona loss, causing the increase of the active power loss and capacitive reactive power of the line. Obviously, the integrated effect of transmission line icing leads the increase of equivalent resistance of the icing line, the leakage conductance and the equivalent capacitance. According to the characteristics that line icing causes the changes of equivalent electrical parameters, this paper puts forward a new icing monitoring principle and algorithm based on the generalized correlation function. The signal source of voltage and current from both ends of the line is used to dynamically generated line icing reference dataset, then on the basis of monitoring data and reference dataset, the maximum of generalized correlation coefficient is used to identify the ice area and severity. The methodology proposed in this paper is different from the current monitoring methodology; additional hardware devices are not required, and the changes of the system wiring are not needed either. On-line monitoring technology of transmission lines icing can be achieved simply by providing the signal source of voltage and current collected by data acquisition device from both ends of the lines.The monitoring methodology put forward in this paper is simple and practical which is strong operability and generality, and it can be used to off-line testing and on-line monitoring. Additionally, the method can also be used to constitute a monitoring device separately or become an important part of the transmission line intelligent monitoring system.