Definitions

Mixture of insoluble degradation products which are formed in an insulating liquid as a result of ageing
IEV ref 212-18-17 [source]

Sum of the sludge resulting from the degradation of the oil (insulating liquid) and the papers (solid insulators)

paper (from IEC Electropedia)
cellulosic paper of certain types, frequently characterized by their relatively high rigidity
Note – In general the term paper is used for cellulosic papers if not otherwise specified. [source]

Kraft paper (from Wikipedia)

Electrical insulation paper (from Wikipedia)

(paper) board (from IEC Electropedia)
generic term applied to certain types of cellulosic paper frequently characterized by their relatively high rigidity
Note – For some purposes, materials of grammage (mass in grammes per square meter surface area) less than 225 g/m² are considered to be paper, and materials of grammage of 225 g/m² or above are considered to be board. [source]

an undesired departure in the operational performance of any device, equipment or system from its intended performance
Note – The term “degradation” can apply to temporary or permanent failure. IEV ref. 161-01-19  [source]

Mineral insulating oil
insulating liquid derived from petroleum crudes
Note – Petroleum crude is a complex mixture of hydrocarbons with small amounts of other natural chemical substances.
IEV ref. 212-17-02 [source]

Natural esters (from IEC 62770)
vegetable oils obtained from seeds and oils obtained from other suitable biological materials and comprised of triglycerides
IEC 62770, ed. 1.0 (2013-11)

Synthetic organic ester (from IEC Electropedia)
insulating liquid produced from acids and alcohols by chemical reaction
Note – These esters include mono-, di- and polyol-esters.
IEV ref. 212-17-08 [source]

Reclaiming (from IEC Glossary)
elimination of soluble and insoluble contaminants from an insulating liquid or gas by chemical adsorption means, in addition to mechanical means, in order to restore properties as close as possible to the original values or to the levels proposed in this standard
Published in: IEC 60480, ed. 2.0 (2004-10) – Reference number: 3.3.5 – Source: IEV 212-09-05 (modified) [source]

Reconditioning (from IEC Glossary)
process that eliminates or reduces gases, water and solid particles and contaminants by physical processing only
Published in: IEC 60422, ed. 4.0 (2013-01) – Reference number: 3.5 [source]

Depolarization (from IEC Glossary)
process of removing electrical polarization from an electrical insulating material until the depolarization current is negligible
NOTE Depolarization is generally recommended before measuring the resistive properties of an electrical insulating material.
Published in: IEC 62631-1, ed. 1.0 (2011-04) – Reference number: 3.12 [source]

Process of removing insoluble sediments and deposits from the transformer