Dissolved gas-in-oil analysis (DGA) is a sensitive and reliable technique for the detection of incipient fault condition within oil-immersed transformers. The presence of certain key gases is monitored and quantified. There are a number of methods developed for analyzing these gases and interpreting their significance: Key Gas, Rogers Ratio, Doernenburg, Logarithmic Nomograph, IEC Ratio and Duval Triangle. This paper investigates the accuracy and consistency of these methods in interpreting the transformer condition. The evaluation is carried out on DGA data obtained from the local power utilities and from published papers. The data consists of 92 different cases. The key gases considered are hydrogen, methane, ethane, ethylene and acetylene. A MATLAB program was developed to automate the evaluation of the methods.

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For use as insulating liquids in power transformers, palm based oils are gaining worldwide attention as biodegradable alternatives and competitors to the petroleum based oils. However, moisture ingress into insulation oils and its effect on the oil breakdown voltage (BDV) must be studied because moisture in oil can alter the physicochemical property of oil and drastically affects the breakdown voltage. This paper presents a comparative study on effect of increasing moisture content on physical structure and BDV of three palm based insulation oils (Red Palm Oil, Refined Bleached Deodorized Palm Oil (RBDPO) and Palm Fatty Acid Ester (PFAE)) at room temperature. Insulation oil is known to have the ability to sustain its good performance up to certain percentage moisture increase. In this paper, an empirical relationship between the palm based oil BDV and the percentage moisture added was developed to approximate oil BDV at various moisture increases. Fourier Transform Infrared (FTIR) Spectroscopy was employed to investigate changes in the oil samples' functional group to assess the physical changes. This equation has been tested and verified. This equation can be used to estimate the BDV of the palm based insulation oils as their percentage moisture increases.Index Terms -Palm oil, transformer, insulation, palm fatty acid ester, refined bleached deodorized palm oil, Fourier transform infrared spectroscopy, breakdown voltage.