A New Thermal Rating Approach: The Real Thermal Rating System for Strategic Overhead Conductor Transmission Lines Part V Monthly and Annual Accumulative Frequency Distributions of Hourly Real-Time Thermal Rating and their Comparison with Conventional Rating-Risk Curves

A new method is introduced which tests the risk of any conventional ampacity rating derived from fixed value weather parameters. This method indicates that the risk of some commonly used ampacity ratings may be as high as fifteen percent, whereas in the past, normal probability methods applied to the wind velocity and ambient temperature data have shown the risk to be only .02 percent. This conflict is due to not recognizing the probability of wind direction and its associated magnitude. It is also shown that the real time capacity may reach 298 percent of the normal rating, while the minimum capacity is 72 percent of normal. Finally, it is found that the real time conductor temperature for fifty percent of the time is only 47 percent of the conductor temperature used to establish the normal rating, while the load is approximately 45 percent greater than the normal rating for fifty percent of the time.