The operating limit of an overhead power line, often referred to as rating, is the maximum electrical current that is allowed to flow though the line. Since most parts of the power line are in the open air, these limits are largely determined by the weather. Traditionally TSOs use static ratings that are based on rather conservative assumptions of the ambient weather conditions.
MeteoGroup has developed a forecast model which allows for Dynamic Line Rating (DLR) of overhead power lines. The model is based on high-resolution weather forecasts taking local land use and topography into account. The Cigré algorithm is used for computing the conductor rating. Cigré will yield a higher electrical capacity (ampacity) of the power line with increased atmospheric cooling conditions. The DLR model expresses the power line ampacity in terms of % increase over the conservative static rating.
DLR model simulations have been validated with independent ampacity sensor data on a 50km stretch of 150kV power line in the Netherlands. This study shows that the DLR model provides accurate and useful ratings which will help to increase the utilization of the power line. In some situations, the ampacity exceeds 150% of static rating. In addition, running the DLR model in hindcast mode gives insight into the presence and location of the critical power line sections, the so-called “hotspots”. Having knowledge of these hotspots will enable TSOs to closely monitor these critical power line sections and help to maintain a stable grid in situations of high load and low ampacity.