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DGA Background
Fault Types
Technical Paper
Example 1

Dissolved Gas Analysis

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The most important aspect of fault gas analysis is taking the data that has been generated and correctly diagnosing the fault that is generating the gases that have been detected.

We have put together here diagnostic methods for determining type faults. Other methods will be available on future upgrades of this page.

Interpretative or Key Gas Method
Useful if no measured previous dissolved gas history is available. The data is compared to the majority of transformers. Flag limits indicated here are established by NTT and utilitized on NTT reports. Customers can establish different flag limits on our reporting software.

Rogers' Ratios
The advantages to any ratio method are that they are quantitative and independent of transformer oil volume. However, ratio methods can produce incorrect interpretations or none at all. Therefore they should be used in conjunction with other diagnostic methods such as the key gas method. Additionally minimum levels of gases must be present before results of the ratio methods become significant.

Dornenburg Ratios.................(under construction)
This method provides a simple scheme for distiguishing between overheating, partial dischare, and other types of discharges. Rogers' ratio method is a more encompassing method and includes temperature ranges for overheating conditions and some distinction of the severity of fault conditions.

IEEE\ANSI C57.104 Guidelines...(under construction)
This is the IEEE Guide for the Interpretation of Gases Generated in Oil-Immersed Transformers. The guideline interprets the results in terms of transformer serviceability. If you wish to order this standard, check the IEEE Website.

Our apoligizes!

We are in the process of updating our on-line diagnostic software. Improvements will include gassing limits, IEEE Guildelines, and various gas ratio methods.

We are, however, very interested in knowing how valuable this service is to our web site customers. It is through your comments and suggestions that this website evolves.

Please send us your comments regarding this service and how it can be more useful in your maintenance programs.

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