Study of limit concentrations of DBDS and sulfur mercaptan in power transformers

The study presents the results of experimental investigation of finding out the limit concentrations of DBDS and sulfur mercaptan for safe and prolonged operation of power transformers in the local environmental conditions of Saudi Arabia. For experimental investigation of limit concentrations of DBDS and sulfur mercaptan, new oil free of sulfur compounds was acquired. Four specimens of this were spiked with 2.2, 3.9, 5.4 and 10.2 ppm of DBDS and another four with free sulfur mercaptan RSH concentrations of 0.00, 0.52, 1.07, 2.13, and 7.10 ppm. The covered conductor deposition (CCD) tests were performed in accordance with IEC 62535 method on all the specimens. The experimental results indicated that the concentration of DBDS should always be <5 ppm and sulfur mercaptan <1 ppm in the new oils before putting in to the service.