For the last two weeks, we talked about some of the basics concerning testing for furanic compounds and interpreting the results. Next we are going to look when we recommended this testing. While knowing the state of the solid insulation is critical information for any transformer, it may not be the best use of resources to always run furans as a routine test. So let’s talk about when it is most important to analyze the insulating liquid for furanic compounds.
The most obvious time when testing for furans recommended is when you suspect a problem that the testing can help confirm and can help lead you to a solution.
Let’s say that you have run a dissolved gas analysis, and the results are abnormal. The results include a significant quantity of carbon monoxide, indicating that you may have an incipient fault condition involving breakdown of the solid insulation. The laboratory will recommend that you monitor the situation more closely while you further identify the nature and location of the fault condition. This is a consistent “next step” in the maintenance and operation of the unit where one of the long term goals will be to correct fault conditions before they can cause an unplanned outage or unnecessary loss of equipment life. Closer monitoring will entail a shorter than normal interval for retesting the dissolved gas analysis so that the abnormal results can be confirmed and a rate of generation for the combustible gases can be established.
These activities have a higher priority if the fault involves the solid insulation because permanent damage to the paper, and subsequent loss of life for the transformer, is occurring. If significant generation of carbon monoxide is expected, analysis for furanic compounds is recommended to determine whether the paper is actually breaking down.
While our interpretation methods allow for the evaluation of furan results without past history as we discussed in last week’s article, having a baseline for furan results allows for a more reliable determination of active destruction of the solid insulation. Comparing current furans results to the baseline determination allows us to evaluate increases in all five furanic compounds and eliminate the possible confusion that the presence of only 2FAL might cause.
Just as we evaluate the generation rate of combustible gases, it is frequently appropriate to more closely monitor the generation of furans as well. Active conditions where the paper is breaking down may not be consistent and continuous. Closer monitoring and evaluation of both gases and furans may provide valuable information for providing a permanent solution to the conditions that are adversely affecting operation of the transformer.
So, we have identified three very important times for performing analysis of insulating liquids for furans: 1.) Test to obtain an initial baseline of furans for use as a diagnostic aid when abnormal conditions are later suspected. 2.) Test when abnormal dissolved gas analysis results indicate that there may be a fault condition breaking down the solid insulation. 3.) Retest furans at a shorter than normal monitoring interval to allow for closer monitoring of how furan levels are increasing and confirm how rapidly or under what conditions the solid insulation may be breaking down.
Next week, we will look at some situations where it makes sense to run furans as a routine test.