Introduction
One of the most effective and convenient ways to determine the early stages of potential faults in oil-insulated electrical apparatus and to monitor the development is to routinely detect and analyze the concentrations and fluctuations of potential fault gases [1]–[5]. This method has been widely used in power-grid operations and is effective in preventing the occurrence of catastrophic faults. In the past, the technology to detect mixed gas by electrochemical sensors offered effective early warnings of potential faults in electrical apparatus. Today, gas chromatography is widely used to accurately detect the composition of various gases dissolved in oil. Fault development can accurately be diagnosed by using gas chromatography together with various other means such as the Duval Triangle and key gas methods. After extended use, these techniques have been found to have drawbacks, namely, the need to routinely replace or calibrate chromatographic columns and sensors because their properties change with use, and the consumption of calibration and carrier gases with gas chromatography use [6], [7].