An Equivalent Heat Transfer Model Instead of Wind Speed Measuring for Dynamic Thermal Rating of Transmission Lines

Abstract

With the increase in electricity demand, the ampacity calculation based on the dynamic thermal rating (DTR) technology is increasingly significant for assessing and improving the power transfer capacity of the existing overhead conductors. However, the DTR models now available present some inadequacies in measurement techniques related to wind speed. Therefore, it is essential to propose a new model instead of wind speed measuring in DTR technology. In this paper, the influence analysis of various weather parameters on the conductor ampacity is carried out by using the real weather data. Based on the analysis, it is confirmed that the impact of wind speed is significant, especially in the case of the low wind speed. Moreover, an equivalent heat transfer (EHT) model for DTR technology is proposed instead of wind speed measuring. For this EHT model, the calculation of conductor ampacity is realized through investigating the correlation of heat losses between the heating aluminum (Al) ball and conductor. Finally, combined with the finite element method (FEM), the EHT model proposed in this paper is verified by the Institute of Electrical and Electronic Engineers (IEEE) standard. The results indicate that the error of the EHT model is less than 6% when employing the steady thermal behavior of the Al ball to calculate the ampacity. The EHT model is useful in the real-time thermal rating of overhead conductors. It can increase the utilization of overhead conductors while also avoiding the limitation of the existing measurement techniques related to wind speed.

Improvement and sensitivity analysis of equivalent heat transfer model for dynamic thermal rating of overhead lines

“…cs rs ss gs q q q q    (1) Where, q cs , q rs , q ss , and q gs respectively represent the convective heat loss rate, the radiant heat loss rate, the solar heat gain rate, and the internal heat source rate of the Al ball. The solar heat gain rate q ss and the radiant heat loss rate q rs of the Al ball can be easily calculated according to the monitored weather parameters [17].…”

“…The convection heat transfer includes two forms: natural convection and forced convection. The natural convection can be equivalent to the forced convection with wind speed not exceeding 0.2 m/s [17,18]. Therefore, the convective heat transfer of the Al ball can be treated in the form of forced convection.…”

“…Moreover, it is noted that the effect of air gravity is also considered during the solution of fluid field. 4) are determined by the experimental correlation formula [17,20]. First, based on the heat balance Eq.…”

“…Literature [17] proposed a DTR model that did not need to measure the wind speed or the operating state of the conductors, which was called the equivalent heat transfer (EHT) model. The model indirectly reflected the convective heat loss rate of the conductors by monitoring the steadystate thermal behavior of an ideal aluminum (Al) ball, so as to realize the evaluation of the conductor ampacity.…”

“…3 Thermal behavior of ideal Al ball and Al ball with support rodIn the EHT model, the parameters a and b in the convection heat transfer of the Al ball as shown in Eq. (4) are determined by the experimental correlation formula[17,20]. First, based on the heat balance Eq.…”