Wind Variability and Its Effect on Transmission Line Capacity Estimation

TL;DR

This paper examines how wind velocity averaging methods influence Dynamic Thermal Rating calculations for transmission lines, revealing significant impacts on ampacity estimates and emphasizing the importance of choosing appropriate averaging techniques.

Contribution

It introduces a comparative analysis of vector and hybrid averaging methods on wind data and their effects on DTR calculations, highlighting the importance of averaging choices.

Findings

Averaging significantly affects Nusselt number and ampacity estimates.

Parallel wind averaging underestimates ampacity by over 10%.

Perpendicular wind averaging can lead to unsafe overestimations.

Abstract

This study investigates the impact of wind velocity averaging on Dynamic Thermal Rating (DTR) calculations. It is based on a high-temporal-resolution (1 second) wind measurements obtained from a transmission line in Slovenia, Europe. Wind speed and direction variability are analysed, and two averaging methods, namely vector averaging, where velocity is averaged as vector, and hybrid averaging, where speed is averaged as scalar, are employed. DTR calculations are performed on both high-resolution data and averaged data (5 minute averaging window). It is demonstrated that averaging has a significant effect on both Nusselt number and ampacity, and the effect exhibits a strong angular dependency on the relative angle of the wind to the line. Therefore, two limit cases are studied: in the case of parallel wind, averaged data underestimates the ampacity, and there is a significant amount of cases where the underestimation is larger than 10 %. In the case of perpendicular wind, the two averaging methods affect the results in different ways, but both result in a substantial amount of cases where ampacity is overestimated, potentially leading to unsafe operation. The main takeaway of the study is that averaging wind velocity has a significant impact on DTR results, and special emphasis should be given to the averaging method, as different methods affect the results in different ways.