Identification of elemental sulfur in mineral insulating oil - Standard corrosive test (DIN 51353) vs. Analytical approach

The intent of this work was to evaluate and compare the capability of two methods to identify oil samples that might present a risk for the power transformer. In the last decades, a number of transformer failure cases reported the corrosion of silver contacts in tap-changers. Some of these failures were linked to the presence of elemental sulfur in the transformer mineral oil. The recommended standard test to identify silver corrosion in transformer mineral oil is the DIN 51353. This test is time consuming and is subjective to a visual rating process; hence, the use of a rapid and reliable analytical method for elemental sulfur detection is of critical importance.