Investigation into the formation of copper sulphide in oil filled electrical equipment

The deposition of copper sulphide within oil filled high voltage equipment is the symptom of the use of sulphurous oil. In some cases, severe copper sulphide contamination has resulted in expensive equipment failure. It has been shown that sealed equipment, containing sulphurous oils and operating at elevated temperatures, are the more susceptible to the copper sulphide deposits. Recent work has suggested a mechanism for the deposits in the paper covering the copper conductors. Other work has suggested that the deposition may be the result of thermally driven gassing. However, the overall mechanism of copper sulphide formation and its deposition on the copper is still a topic of interest.