Overview: Online Measurements of Transformer Fault Gases

Thomas, Waters, B.S. Chemist
Kristin Williamson, M.S. Chemist
Dr. Douglas Ritchie, PhD Physicist
SERVERON, INC

The dissolved gas analysis technique (DGA) is well known to the transformer engineering community. Equally well known are some of the limitations of this method for analyzing transformer fault gases (H2, O2, CO, CO2, CH4, C2H2, C2H4, C2H6). Further, it is widely knownthat knowledge of the concentrations of these gases dissolved in oil (especially the combustible gases) is critical to safe transformer operation and management.

Serveron has developed and deployed an online system that eliminates most of the aforementioned limitations and a system that provides near real time information on transformer gassing, with an ability to access this data from a remote location.

FUNDAMENTALS
If the transformer is a conservator design, there of course is no headspace. In these cases the analysis must be done by direct contact with the oil in the transformer main body. However, in the case of a headspace transformer, one has a choice. Measurements can be made utilizing a sample of gas taken from the headspace (especially if the transformer has a leak tight or low leakheadspace) or the measurements can be made from the oil.

Both will provide data on existing transformer fault gases. This paper presents data taken from a headspace transformer simultaneously outfitted with both types of analysis equipment – a headspace analyzer and an oilphase analyzer.

The questions of merit that are addressed in this paper are:
· Details on the instrumentation utilized
· Details concerning the subject transformer
· A clear description of the installations used to gather these measurements
· Precision measurements of gas-in-gas (transformed to oil equivalents) for all eight fault gases
· Precision measurements of gas-in-oil for all eight fault gases
· Comparisons of the two measurement techniques, with conclusions as to any differences seen between the two types of instrumentation, and conclusions about the dynamics oftransformer fault gases.

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SERVERON (EPRI Substation Equipment Diagnostics Conference (2/2001))