Effect of time resolution of meteorological inputs on dynamic thermal rating calculations

Dynamic thermal rating (DTR) of power transmission lines can provide a significant increase in transmission capacity compared to the more traditional static rating. This gained capacity can be used to increase the normal and emergency operational flexibility of power transmission systems. Ampacity values can be determined either directly or indirectly from sag or ambient weather conditions. The most important inputs to weather-based DTR systems are meteorological data. The data can be obtained in the form of instantaneous or averaged values, and with various sampling/update intervals. This study examines the effect of the character of the meteorological inputs on the performance of DTR calculations. The analysis is based on real high-resolution wind and temperature measurements. Owing to the random character of the updates with instantaneous weather data, the averaged inputs provide more accurate estimates of ampacity and temperature. Update intervals of 10 minutes are sufficient, while longer intervals cause significant calculation errors. This could lead to a substantial risk of conductor thermal overload. The presented results can be used for effective data management in DTR systems. They can help to avoid substantial errors in ampacity calculations, thus minimising the risk of transmission system outages and premature ageing of transmission conductors.