Rapid analytical method for elemental sulphur detection in power transformer insulation

Over recent decades there have been reported failures of oil/paper-based transformers caused by corrosion of copper conductor surfaces and breakdown of insulation. A small number of failures were caused by silver corrosion in tapchangers, promoted by the presence of elemental sulphur at mg/kg levels. The electrical power infrastructure and the entire transformer fleet can be at risk from unexpected failures, so preventive measures are necessary. In this work a rapid analytical technique to monitor elemental sulphur levels « 1 mg/kg) in insulating mineral oil has been developed. The method can be used as a routine test, or to confirm the presence of elemental sulphur in samples where corrosion has occurred. The potential of the method is demonstrated through its application to some real mineral oil samples from transformers.