POLLUTION DEPOSITION ON HV INSULATORS –
UNTAPPED RESOURCE FOR ATMOSPHERIC CORROSIVITY ESTIMATION.

Peter W. Haberecht PhD MEng
Materials and Environments (MATENV) Melbourne AUSTRALIA

This paper presents work from the PhD thesis and relates the deposition of high voltage insulators to that of other approved salt or pollution deposition measuring techniques found in atmospheric corrosivity assessment procedures. This work was conducted over 6 years and shows a very high correlation between the deposition rate on high voltage insulators and atmospheric corrosivity measurement of zinc. This work draws upon an extensive corrosion study at 15 sites in New Zealand (1816 tests) for in excess of 12 months and co-operative research in South Africa.

This work proposed a simple model based on the international HV Insulator pollution deposition standard technique IEC60815 in conjunction with IEC60507 which are used throughout the world as a cheap method to predict the probability of ‘arcing-over’ the high voltage supply and cutting off the power at the relays at the switch yard causing a blackout. The results achieved in the extensive study throughout New Zealand were outstanding and proved the ability to apply and transport this proposed model. The next step was to review the available data on deposition rates on insulators provided by the electricity distribution companies around the world and the associated geographic and weather details to determine the atmospheric corrosion rate of zinc at the same site based on ISO9223 ‘Atmospheric Corrosivity’ methodology. The measured pollution deposition rate on the sheltered insulator bottoms at 85 sites around the world accurately predicted 87% of the ISO corrosivity categories (based on zinc corrosion) for these sites. Results from equatorial Asia appear to be non-compliant and warrant further investigation.

This study found that the ISO9223 wet salt candle and the average annual deposition rate on the HV glass insulator bottom surface provided relatively similar deposition results. It is proposed that the deposition onto insulator surfaces may be a more relevant method as it replicates deposition on large surfaces.

This simple methodology requires: 3 HV insulators; 1 litre of water; a bucket; a conductivity gauge; and a conversion table; to determine the level of surface contamination. This work predicted with 87% accuracy the ISO 9223 atmospheric corrosivity rates for zinc at numerous sites in China Japan Jordan Korea Saudia Arabia Sweden Tunisia United Kingdom and USA.

The implications from this research are significant with the cost of atmospheric corrosivity studies becoming prohibitively expensive this method converts technically valid surface deposition results (pollutants) currently provided by the high voltage electrical engineers from around the world (provided at no cost) into valid empirical corrosivity rates from often remote locations.
 

NOTE: Uncertain if this should be in this stream or TEG100X (Vinod). Please determine the appropriate stream as there is no atmospheric corrosion stream

Regards

Dr. Peter Haberecht

Member ISO TC156 Committee