Detection of Carbonization of Paper in Transformers Using Duval Pentagon 2 and Triangle 5

Abstract

The two most dangerous faults in transformers are arcing in paper insulation and thermal carbonization of paper inside windings. Both may result in catastrophic failures of the transformers. However, these faults are very difficult to detect. Furans content and the CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /CO ratio can be used, but they are often unreliable or not sensitive enough when small amounts of paper are involved. Furthermore, they cannot identify the exact location of the fault. Acoustic tests may be used for that purpose, but they are expensive and can be applied only to a small number of transformers. New inexpensive methods have been developed recently, using DGA and Duval Pentagon 1 and Triangle 1, to detect arcing in paper and differentiate it from arcing in oil. Duval Pentagon 2 and Triangle 5 have been used in the present article to detect faults C with thermal carbonization of paper and their location in transformers, i.e., in windings turns (the most dangerous) or in leads entering or exiting the windings. This offers the practical advantage of concentrating maintenance efforts of transformer operators on possible faults C with carbonization of paper in windings turns, which occur in a small number of transformers but may result in severe failures and outages.