Decreasing Behavior of Acetylene in Oil-Immersed Transformers

Abstract

In diagnosis of faults by means of dissolved gas analysis for oil-immersed transformers in service, acetylene gas generated owing to faults accompanied with high temperature such as arc or partial discharge is designated as a characteristic gas. Even if small quantities of acetylene gas are detected, successive monitoring frequency for the transformer is generally increased.
It is reported that occasionally concentrations of acetylene gas dissolved in oil show decreasing behavior with operating time differing from other generated gases. Authors have taken notices of the behavior and made clear that it can be analyzed by the rate equation of first-order reaction, assuming that the behavior depends on a chemical reaction of acetylene gas to any material included in a transformer. We have had experiments using copper foils as a possible material reacting to acetylene and confirmed that the behavior of acetylene in transformers can be reproduced in a laboratory. We studied chemical bonds formed on the surface of the copper foil heated in oil dissolved acetylene gas using XPS. For exact calculations of quantities of acetylene gas generated abnormally, the reacting quantities of acetylene gas have to be taken in consideration.