A1: Transformers need to be tested on a yearly basis, at least. Transformers that are built for a specific purpose such as wind farms, solar farms, electric locomotives and furnace transformers should be tested at shorter intervals.
A2: No, the whole process starts with a good sample and this must be done correctly. Instead of a plastic container, a new tin or glass syringe should be used. Glass bottles can also be used where there are security requirements, but from a lab safety viewpoint, these sampling containers should only be used in specific cases.
A4: This is information is extremely important. The first and most important information is the serial number, as this is used to link all the results in the database. Next, the electrical rating of the transformer is used to determine the specification class, which determines the permissible limits for the test results.
A5: No, only in extreme cases. The diagnosis of transformers is largely based on the trends of repeat samples.
A8: The diagnosis of the DGA levels is complicated and, although there are limits that can be used for alarm purposes, the diagnosis also depends on history, trends, production rates, type of industry/transformer application, age of transformer, etc.
A9: The diagnosis of the furanic level is based on the trend and production rates for the furanic components. While a 200 level (or lower) reading is worrying, it does not mean that the transformer is at the end of its lifespan. It does, however, indicate that the transformer could fail prematurely if the condition is not managed. The sampling period for this transformer needs to be shortened and planning for a new transformer may have to begin.
A10: No, furanic testing only applies to equipment containing paper-based insulation material.