WG B2.69 Coatings for Power Network Equipment

There have been numerous advancements made in the last decade regarding surface engineering techniques and surface coatings which allow the introduction of important properties such as self-cleaning, icephobicity, and anti-corrosion. These properties benefit the power industry in terms of increasing the reliability of transmission assets, as well as enabling the reduction in the capital cost of new constructions.

Working Group B2.69 has progressed work done by previous B2 working groups and has focussed on increasing the reliability of power networks in various environmental conditions as well as responding to environmental concerns caused by corona noise and visual aspects of overhead power networks.  The Australian member of this working group was Francis Lirios.  The scope of the working group involved insulators, conductors and fittings, metallic structures, and overall appearance of overhead lines. Two Technical Brochures have been produced.  The first is TB 837: Coating for improvement of electrical performance of outdoor insulators under pollution conditions. The second is TB 838: Coatings for protecting overhead power networks against icing, corona noise, corrosion and reducing their visual impact. The discussion below is about Technical Brochure 837, with TB 838 to be featured in next month’s article.

TB 837

TB 837 starts with a general discussion on the existing and foreseen pollution level which is the main criteria that dictates the design requirements for outdoor insulators, as well as the improved performance of insulators with a hydrophobic surface against flashovers. Currently, silicone is the material of choice that provides hydrophobic characteristics that meet the required performance as well as providing the possibility of using a shorter length of insulator.

The different types of insulators with hydrophobic characteristics that are commercially available were discussed, including composite insulators, hybrid insulators and ceramic greased insulators as well as coated-ceramic insulators with a thin layer of silicone RTV (Room Temperature Vulcanizing) rubber along the insulator surface.

The earliest application of RTV coatings were done on site and considered as a remedial measure. In the past few years however, more utilities are using this solution pre-installation which saw the number of cap and pin insulators considerably increase from a few thousands to about 10 million units in 2020. This is expected to reach 100 million units by 2030 and the Working Group highlighted the need for a standard to specify and assess the quality of the RTV coating and of coated insulators. An informative section on RTV coatings will be provided in the latest update of IEC 60383-1 Standard for insulators, but its user specifications are most often derived from a combination of CIGRE Technical Brochures, TB 478 and TB 595, IEEE guidelines, various national standards and from existing IEC Standards.

Finally, based on more than 30 years’ experience, guidelines for RTV coating procedures, for laboratory testing to verify product quality and for diagnostics to assess the insulator field conditions are reported.

TB 837 is on e-cigre free to members and €240 for non-members.