In a long 130 years of its journey in service to mankind, the power transformer has grown in many aspects; ratings, performance, technology, aesthetics and ecofriendliness. Today, the transformer industry is witnessing the era of shifting from petroleum based mineral oils that are depleting, environmentally unfavorable, and proven dangerous to natural esters (vegetable oil based) that are renewable, environmentally friendly, and non-hazardous. The market and regulatory pressures to reduce liability risk exposure of mineral-oil-filled distribution and power transformers are increasing. In addition, there are demands to improve equipment efficiency and adopt more "earth-friendly" options in our power systems. In the last two decades there has been a resurgence of usage of natural ester insulating liquids for their "GREEN" and Safety credentials. These renewable resources have good dielectric properties and are compatible for use in power transformers. This paper evaluates and relates the new natural ester oil with existing mineral oil technology in terms of environmental concern, fire safety, physio-chemical properties, thermal performance, and dielectric performance. It also covers key modifications in design, manufacturing and operation to help assure excellent functionality and long life. In brief, this paper provides transformer designers and users about the advantages and challenges of "Green Insulating Liquid". Due to the voluminous properties that are compared and discussed, this paper is presented in two parts: Part 1 discusses on key properties and standards for the two liquids. Part 2 emphasizes on additional key properties and material compatibility related to electrical design. Based on evidence discussed in both parts, it is concluded that natural esters are acceptable for both new transformers and for retro filling existing units.
Dissolved gas analysis (DGA) is proving to be the most promising and simplest tool for condition monitoring of transformer. The experimental results of the level and the change in concentration of different combustible gases dissolved in the insulating oil is a trustworthy diagnostic tool which can be used as indicator of undesirable events developing inside the transformer, such as hot spots, electrical arcing or partial discharges. Several DGA diagnostics methods (expert systems) are available to interpret different incipient faults in transformers. The paper showcases the implementation & diagnosis of all expert system in 1single MATLAB program to reduce the analytical time and human errors. Paper also discusses 4 different cases to interpret the transformer condition and incipient faults using MATLAB program. Also, it compares interpreted data using different expert system with actual fault found in transformer. The objective of this paper is mainly to analyze available data from DGA to arrive at conclusion of type of fault to further investigate or to save the transformer and correlate the fault found with DGA data.
Keywords-Dissolved gas analysis (DGA), MATLAB, Transformer, partial discharge, buchholz relayI.
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