Comparison between duval triangle and duval pentagon method for dissolved gas analysis of power transformer

Abstract

Power transformers are the highest value of the equipment installed in high-voltage substations, comprising up to 60% of total investment. There is a need for economic and financial reports to be provided to make asset decisions and ensuring balance between investment, maintenance costs and operational performance. Health index (HI) is the most common approach used in determining the condition of the transformers. It is a tool that process information by creating a score that describe the condition of an asset. A comparative analysis is made between HI calculation models that allow the evaluation of the condition of a power transformer. Through this index it is possible to objectively determine the condition of power transformers to make maintenance or reinvestment decisions. Thus, it is possible to detect possible risk assets preventing them from failing, allowing an increase in the life time. Several studies have examined different power transformer condition assessment and life management techniques. These techniques include measuring or monitoring of dissolved gas analysis (DGA) using Duval Triangle method. DGA technique is a reliable method and widely used to detect incipient faults which may occur in transformers such as partial discharge, thermal fault and electrical fault. This paper will focus on DGA using Duval Triangle & Pentagon method. The objective of this paper is to compare and identify between Duval Triangle and Duval Pentagon methods which may provide more accurate interpretation of DGA test result. This comparative study is based on real data provided by Malaysia utility company. The analysis using Duval Pentagon method give the accurate fault analysis and exactly same as the interpretation given by IEC 60599 Standard. An accurate fault analysis using Duval Pentagon Method give a better output of life time prediction, types of possible faults and recommendations for future maintenance action can be achieved.