Furan Testing - Part 4Technical Briefs
Testing for Furanic Compounds in Insulating Liquids Part 4 – When do we test for furans? (more)
In Part 3, we talked about three times where it makes good sense to test insulating liquids for furanic compounds. These were examples of "non-routine" occasions when testing for furans is a good idea. There are also a couple of situations where performing the analysis on insulating liquid during every routine sampling and testing interval is appropriate. We are going to describe those situations next.
For very large, expensive, or critical oil-filled transformers, the "normal" pattern we implied in the last article may not be appropriate. If a routine dissolved gas analysis is performed and then, when the DGA is abnormal, it is followed up by an analysis for furanic compounds, this may create an unsupportable time lag where equipment or critical loads are concerned. The potential loss of insulation life during the time between tests may represent a significantly higher cost than the cost of including the furans analysis as a routine test.
A second, similar situation relates to silicone fluid-filled equipment. Silicone fluid may break down a little under normal conditions in an operating transformer. This does not represent much of a difficulty from an operations standpoint, as the fluid will continue to perform satisfactorily. However, the byproducts of the fluid breaking down include carbon monoxide and carbon dioxide. Interpreting dissolved gas analysis in silicone fluid-filled electrical equipment takes this generation of the carbon oxides into account. Generation of carbon monoxide by breakdown of the fluid means that evaluating that gas to monitor the solid insulation is not as accurate. Except for very small distribution class silicone fluid-filled transformers, including analysis of the insulating liquid for furanic compounds is recommended during every routine sampling and testing interval, so that the condition of the solid insulation may be more accurately monitored.
So far, we have discussed how furan analysis may be used to determine whether the solid insulation in a transformer has broken down, and whether the condition that caused this continues to be active.
In Part 5, we will talk about what levels of furans we consider to be significant.