Field observations of wet snow accretion on overhead transmission lines at the Kushiro test line

Wet snow accretion on overhead lines often causes large-scale snow damage. The Kushiro test line, Japan, was constructed in 2013 for field observations of wet snow accretion in conductors and insulators as well as galloping resulting from snow accretion in overhead lines. Several cases of noticeable wet snow accretion have been observed at this site, especially in the winter of 2014. In the most notorious case, more than 2 kg/m of snow was found to be accreted on the ACSR240 single conductor, which has a diameter of 22.4 mm. In the case of single conductors without countermeasures, snow accretion developed to form a cylindrical sleeve with wire rotation. However, in some cases, the cylindrical sleeve of snow accretion also occurred in four-bundled conductors, where line spacers prevent the wire from rotating. This indicates that the accreted wet snow slides along the strands of the wire to form a cylindrical sleeve. Accordingly, the effectiveness of the snow resistance ring, which is the most commonly used anti-snow-damage device in Japan, in preventing snow accretion was confirmed. As the ring prevents the accreted snow from sliding, accretion areas tend to split, causing the snow to be shed from the conductor. More heat transfer from the air to snow and heat generated by the electric current facilitated the sliding of snow along the strand, making the snow resistance ring more effective. •Kushiro test line was constructed for field observations of wet snow accretion.•Over 2 kg/m of snow was accreted on ACSR240 single conductor.•Snow accretion was developed to form a cylindrical sleeve with a wire rotation.•Accreted wet snow slid along strands of the wire to form a cylindrical sleeve.•Effectiveness of snow resistance ring in preventing snow accretion was confirmed.