A case study of glass insulator pin failure in 500 kV transmission line

This work investigates the causes of the failure of an insulator pin at tower 639 of the 500 kV transmission power line (TL) Tucurui-Vila do Conde in the State of Par ' a, Brazil. Such a tower is of one the highest in this TL and is located at one bank of the large Moju river, in the Amazon Forest region. The failure was caused by stress corrosion cracking of the galvanized 1045 steel pin. Detailed investigation of the failed pin, of the design of the insulators and of the maintenance procedure did not reveal errors that could indicate incompetence, recklessness, or technical negligence. After several analysis (chemical, microscopic and environmental), it was concluded that the root cause of the failure proved to be associated with a novel phenomenon. Illegal extractive activities and wildfires generated pollution, and the lack of natural filters/obstacles allowed the generation of a polluted microclimate at the top of the higher towers mounted at the two riverbanks. This accelerated the stress corrosion of the pin.