Study on the Effectiveness of Thermal Constraints in DLR Applications on Overhead Transmission Lines

With the increasing penetration of renewable energy and rising power demand, the efficient utilization of existing transmission infrastructure has become a key issue in power system operation. However, in South Korea, conservative Static Line Ratings (SLR) based on worst-case weather conditions are still applied, while new transmission development faces significant environmental and social challenges. As a solution, Dynamic Line Rating (DLR) has gained attention for its ability to reflect real-time weather data, but its implementation remains limited due to infrastructure and operational constraints.<br/>This study explores an alternative approach by applying Seasonal Line Ratings (SAR) based on long-term historical weather data provided by the Korea Meteorological Administration. Using IEEE Std. 738, seasonal ampacity values were calculated, and PSS/E simulations were conducted to quantitatively evaluate the impact of SAR on mitigating thermal constraints. The results show that SAR application can reduce the frequency of thermal overloads by up to 45%, and during winter conditions, available line capacity increased by up to 14% compared to conventional ratings.