ABSTRACT
To ensure the provision of reliable and uninterrupted electric power supplies, it is essential to routinely monitor the condition of installed high-voltage power system components such as transformers (Chiesa, 2010). A number of methods are conventionally used by the industry for checking the condition of such high-voltage transformers. These include the analysis of gases dissolved in the electrically insulating oils referred to as Dissolved Gas Analysis (DGA). The relative amounts of different gases present give an indication of possible developing faults such as overheating, electrical breakdown and so on (Duval diagram) (Wang, 2000). In addition, laboratory testing of the oil for the amount of water and acid present along with the dielectric strength of the oil can be used as indicators of incipient faults. The colour of the oil via colour index (CI) is used as a further indication of abnormalities (Golden et al., 1995).
