The purpose of this study is to determine whether the currently applied conditionmonitoring (CM) techniques are sufficient and effective for early detection of coppercorrosion fault in transformers and to establish a more relevant CM technique forearly detection of such fault. In this study, experimental work is carried out byapplying appropriate methods on different commercial insulating mineral oils for thedetection and identification of additional related by-products of copper corrosionprocess, if any. The major finding of this experimental investigation includesidentification of additional by-products, which could be useful to establish a moreeffective CM technique. Furthermore, the role of sulphur compounds in coppercorrosion fault is considered, and a relevant reaction mechanism of formation CSD isdeveloped based on the findings of the related by-products. It is concluded that, theapplication of a relevant CM technique is necessary for establishing a cost-effectivecondition based maintenance (CBM) to minimize the economic losses, hazardous effectson human life and the environment.