Furan test is used to determine the life of a transformer and condition of transformer oil in transformer oil. By the Furan analysis, we check the condition of paper in transformer oil. Furan measures the degradation of cellulose paper. The degradation materials produce CO and CO2 gases.
When the paper of the degree of polymerization reduces, then the mechanical strength of the transformer decreases. The polymerization degree of paper directly related to the concentration of furan derivatives in oil.
Furan is an aromatic compound. It is the combination of four carbons with hydrogen and one oxygen. The molecular formula of furan is C4H4O. Furan indicates the abnormal stress, overheat, short duration in a transformer.
Analysis of Furan Testing:
The transformer consists of both paper and oil. When the paper insulation ages, the mechanical strength of the transformer decreases. The Degree of Polymerization (DP) is a measure of the length of the cellulose chain. The value of length cellulose chains for fresher paper and at the end of life is 1000-1200 and 150-200 respectively.
The degradation of paper insulation mechanism is accelerated by temperature, water, and oxygen. When the measurement of furan count is above than 2500 ppb (parts per billion) then it indicates that the transformer is about to fail. The analysis of furan test has occurred with the help of high- performance liquid chromatography (HPLC).
Procedure for Furan Testing:
Take a microlitre of oil for sampling and placed the oil in a chromatographic separation using column by using a mobile phase. The analytes remain on the stationary phase of the column with varying degrees of force due to the polar interaction. The testing sample will be divided into individual analytes.
The specify chemical constituent will gradually elute. And it will be recorded by a UV detector after separation at retention time. In this furan derivation process, five derivatives are detected. They are 5-Hydroxymethyl-2-furfurol, 2-furfuryl alcohol, 2-furfurol, 2-acetylfuran, and 5-methyl-2-furfurol.
Furan/furfurol derivatives can help to determine the condition of paper insulation in the transformer. This allows the device to automatically shut down and detailed inspection of inside the device to be considered only once increased values have been detected. The detected increase value is measured in the unit of mg/kg (ppm).
The insulating paper is the main insulator of the transformer. If the insulating paper damage then the transformer will get damaged. So Furan test is an important test for the transformer.