Numerical simulation of overhead power line cooling in natural convection regime

Abstract

The complexity of the electrical power systems and increasing demands for electrical power constantly pressure the transmission system operators to utilize existing power lines more effectively and safely. The transfer capability of the power transmission lines, i.e. the maximal allowed current, is often limited by the maximal temperature of the overhead line that should not be exceeded in order to avoid excessive sags. There has been substantial work done on Dynamic Thermal Rating (DTR) of overhead lines in last few decades, which is summarized in leading standards, namely IEC, IEEE and CIGRE. All three standards model the convection as an empirical relation that agree well in wind regimes above 0.6 m/s, however, their predictions in low wind regimes differ considerably, which casts doubt on model reliability and consequently diminishes its usability in operative use. Besides, the transmission capacity is often still determined for worst case weather conditions, e.g. ambient temperature of 40deg C, with no rain and no wind.