How Can Temperature Data Be Used to Forecast Circuit Ratings?

A transmission cable system is generally surrounded by soil that results in large thermal time constants, which means that the conductor temperature changes can take time even though there are sudden changes in system loading conditions. The load forecasting is based on statistical analyses of historical data to determine circuit rating or overload capability while the dynamic line rating makes use of the prevailing load information and ambient weather conditions to establish the dynamic rating for the circuit. The chapter describes many different ratings that are adopted by utilities. It offers a brief review of the cable rating calculations. The chapter provides a description of several real‐time temperature rating (RTTR) tools that are commercially available to utility engineers who are operating their assets near their operating limits. Implementing an RTTR system requires capital investment (computer, software, and SCADA) in addition to the investment made for the distributed temperature sensing itself.