Introduction

The degradation of cellulosic materials constituting the solid insulation of oil-filled electrical equipment leads to the formation of several compounds specific to cellulose decomposition, such as sugars and furan derivatives.

The furan derivatives, of which a large proporation remains adsorbed on the paper, are nevertheless slightly soluble in oil. Their presence can be used as a diagnostic tool to equipments in service and to supplement information from dissolved gas analysis.

1 Scope

This International Standard specifies test methods for the analysis of 2-furfural and related furan compounds resulting from the degradation of cellulosic insulation and found in mineral insulating oil samples taken from electrical equipment.

2-furfural and related furan compounds dissolved in mineral oil are analysed by high performance liquid chromatography(HPLC). Prior to high performance liquid chromatography(HPLC) analysis, furan derivatives are extraced from the oil by use of a suitable extraction method such as liquid-liquid extraction (method A) or solid-phase separation on a silica cartridge (method B).

2 Normative references

The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.

IEC 475:1974, Method of sampling liquid dielectrics.

IEC 567:1992, Guide for the sampling of gases and of oil from off-filled electrical equipment and for the analysis of free and dissolved gases.