Definitions

Sulfur hexafluoride (SF6) is an inorganic, colorless, odorless, non-flammable, extremely potent greenhouse gas, which is an excellent electrical insulator
From Wikipedia [source]

SF6 complying with IEC 60376, and never used previously
Published in: IEC 60480, ed. 2.0 (2004-10) – Reference number: 3.3.2 [source]

SF6 never been introduced into electrical equipment (e.g. gas having been transferred into a storage tank)

Published in: IEC 60480, ed. 2.0 (2004-10) – Reference number: 3.3.3 [source]

SF6 introduced into electrical equipment
Published in: IEC 60480, ed. 2.0 (2004-10) – Reference number: 3.3.2 [source]

device that enables one or several conductors to pass through a partition such as a wall or a tank, and insulate the conductors from it.
Note 1 – The means of attachment (flange or fixing device) to the partition forms part of the bushing. The conductor may form an integral part of the bushing or be drawn into the central tube of the bushing.
Note 2 – The bushings may be of the following types:

– liquid-filled bushing;
– liquid-insulated bushing;
– gas-filled bushing;
– gas-insulated bushing;
– oil-impregnated paper bushing;
– resin-bonded paper bushing;
– resin-impregnated paper bushing;
– ceramic, glass or analogous inorganic material bushing;
– cast or moulded resin-insulated bushing;
– combined insulation bushing;
– compound-filled bushing;
– gas-impregnated bushing.

Source: IEV ref 471-02-01

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
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
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]