Power transformer cellulosic insulation destruction assessment using a calculated index composed of CO, CO 2 , 2-Furfura
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ORIGINAL RESEARCH
Power transformer cellulosic insulation destruction assessment using a calculated index composed of CO, CO2, 2-Furfural, and Acetylene Ashkan Teymouri
. Behrooz Vahidi
Received: 21 June 2020 / Accepted: 19 October 2020 Springer Nature B.V. 2020
Abstract Power transformer insulation is degraded and decomposed over time. Due to the importance of cellulose, indicators such as 2-Furfural, CO, CO2, and CO2/CO ratio are used to investigate cellulose aging status because these are cellulose degradation products. However, various studies have shown that using each of these indicators alone may lead to incorrect cellulose degradation diagnosis. Therefore, a new calculated index called CFA index (an abbreviation of Carbon, Furfural, and Acetylene) that considers the effects of four indicators (CO, CO2, 2-furfural, acetylene) together will be presented in this paper. The CFA index has been obtained from the analysis of 216 power transformer measurement data using the correlation coefficients calculation. The reason for considering acetylene is the importance of its production and the high correlation coefficient between acetylene and transformer age. In this method, if the transformer has the CFA index between -2 and -5.3, then it can be ensured that the transformer does not suffer from severe cellulose aging or decomposition. The normal range for the CFA index is obtained from investigating data from many power transformers, all with CO2/CO ratio between 3 and 10. Finally, to verify the accuracy of the CFA index and its ability to detect cellulosic insulation degradation and the inefficiency A. Teymouri B. Vahidi (&) Department of Electrical Engineering, Amirkabir University of Technology, Tehran, Iran e-mail: [email protected]
of other methods in some cases, dissolved gas analysis (DGA) test results of 306 power transformers will be investigated, and results will be fully presented. Keywords Acetylene Cellulose aging CO2/CO ratio Correlation coefficients CFA index 2-furfural (2-FAL)
Introduction Transformers consist of an oil-paper insulating system. During the transformer life, the oil can be physically or chemically refined and even replaced. However, the paper cannot be repaired or replaced from the beginning, and it undergoes irreversible changes over time (Teymouri 2019). Transformer cellulose ages due to the presence of heat, moisture, and oxygen. These changes are inevitable and are called aging (Vahidi et al. 2019). Owners whose transformers are old face two technical and financial difficulties. Because if they don’t replace their transformer, they run the risk of unplanned failure, which will cost both the transformer and the service cost. On the other hand, if they proceed with the early replacement of the transformer, they will still incur additional fees if the transformer is in service and may even serve for more years (Teymouri 2017).
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Cellulose
Therefore, cellulose aging condition is essential for transformer monitoring
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