A proposed method for rationalizing the risks of seasonal transmission line ratings

A method is proposed for rationalizing the risk of transmission line overcurrent between seasons. An expected per-unit exceedance (EPE) is calculated from historical weather data to measure overcurrent risk. Using the EPE the overcurrent risk now accepted by transmission lines rated using a deterministic process is examined. The actual risk assumed when using ambient weather criteria to rate transmission lines varies between lines and is inconsistent throughout the year. The proposed method applies the same level of risk to a summer rating that is currently accepted for a winter rating of the same transmission line design. The result is a cautious first step towards the implementation of a probabilistic, risk-based transmission line rating methodology