Improved wind model to verify the stability of Wintrack braced post-insulator sets

摘要

A new high voltage overhead line design, generally known as Wintrack, was developed in The Netherlands. The Wintrack design was developed to achieve a reduced magnetic field and an improved aesthetic and more compact appearance. The first Wintrack overhead line was commissioned and taken into operation in 2013.The suspension of the 380 kV and 150 kV phase bundles is achieved by braced post-insulator sets. From literature and experience abroad it is known that braced post-insulator sets, with vertical hinges, may become unstable as a result of unbalanced loading, difference in span length and use of long sections. The maximum allowable oblique angle of the braced post-insulator set is limited by the striking distance between live parts and poles.After discussions with a meteorological institute, a wind model was developed for unbalanced wind loads. The wind model fits with the European standard for overhead lines and is in line with the Dutch climate with respect to gust factor and extreme wind speed.The model for unbalanced wind loading is developed for determination of oblique angles of hinged braced post-insulator sets and to verify whether the stability of a line section between two tension towers is acceptable. The stability depends on a large number of parameters, such as length of the line section, span length, tower height, small line angles, height difference between adjacent towers and stiffness of the poles. The stability of the existing and planned Wintrack overhead lines is checked with the improved wind model using the PLS CADD transmission line software. From the stability calculations it was concluded that C-yokes may be used in hinged braced post-insulator sets. The effect of asymmetrical loading has to be taken into account. For planned Wintrack overhead line routes it is envisaged to apply suspension chains to connect conductors to the braced post-insulators.