Thermal rating of Transmission Lines Based on Distributed Parameters

Generally, centralized parameters and average temperature of conductor are used in calculating thermal rating of transmission line, the result of which may not be accurate enough for a long-distance line. This paper presents a new method to calculate ampacity base on the distributed parameter model. Firstly, given measures of the voltage and current phasors at both ends of the transmission line and the environmental parameters along the line, the weighted least squares (WLS) state estimation is set up to estimate the distributed resistances of line; And then, the distributed temperatures of line are obtained through the nonlinear relationship between resistance and temperature; Finally, the maximum temperature of those line segments temperatures is taken as the temperature of the line to calculate thermal rating of the whole line. Example results prove the method is efficacious and reasonable.