OELCHECK test instrument: Perkin Elmer Flexar HPLC
Sample quantity: approx. 10 ml
Unit: mg/kg (ppm)
Test result: furan derivatives from paper insulation dissolved in oil
Analysis for: insulating and transformer oils
Brief description:

The transformer oil is absorbed in a few milliliters of pentane. The furan and furfurol derivatives are separated from the rest of the oil matrix by means of solid-phase extraction.

A few microliters of the extracted sample are placed on a chromatographic separation column using a mobile phase. Due to the polar interactions, the analytes remain on the stationary phase of the column with varying degrees of force. The sample is therefore divided into the individual analytes. The analytes gradually elute and are recorded by a UV/VIS detector after separation at a characteristic retention time. The following furan derivatives are detected in this process:

  • 5-hydroxymethyl-2-furfurol (5HMF)
  • 2-furfuryl alcohol (2FOL)
  • 2-furfurol (2FAL)
  • 2-acetylfuran (2ACF)
  • 5-methyl-2-furfurol (5MEF)
Statement: The furan and furfurol derivatives for investigation are breakdown products of cellulose. Determining the quantities of furan/furfurol derivatives can therefore help draw conclusions on the condition of the paper insulation, which contains cellulose, drawn into the transformer without requiring the transformer to be switched off. This allows the system to be shut down and a detailed inspection of the inside of the device to be considered only once increased values have been detected.
Underlying test standard: DIN EN 61198, ASTM D5837