In transformer operation, one of the key maintenance ‘musts’ is to ensure that the electrical system remains isolated through effective insulation. This is achieved through the use of special insulating paper (Kraft paper).

However, it is critical to monitor the paper’s tensile strength and degradation, or degree of polymerisation (DP) over time, to ensure that the paper continues to provide effective insulation for the transformer.

Analysis of the paper insulation, however, is a potentially dangerous, expensive and invasive procedure which requires the transformer to be taken out of service.

An alternative, quicker and easier method of testing the paper’s DP is by analysing the transformer oil.

How does analysis of the oil provide information on the paper’s degradation? The link is to be found via furanics, which dissolve in the transformer’s oil. It is generally accepted that the concentration of furanics can be directly related to the degree of polymerisation of the solid insulation in the transformer.

High performance liquid chromatography (HPLC) is a sophisticated analytical technique that is used to determine the degradation of transformer paper by analysing the concentration of furanics present in the transformer’s oil.

WearCheck’s latest Technical Bulletin (no. 54) features an explanation and in-depth discussion of HPLC, when it is used, why it is used, and how it works.

To view Technical Bulletin 54, click here.