NOTE 1 For the use of this document, high-voltage (HV) is defined as the rated voltage above 1 000 V. However, the term medium-voltage (MV) is commonly used for distribution systems with voltages above 1 kV and generally applied up to and including 52 kV.

NOTE 2 Throughout this document, the term “pressure” stands for “absolute pressure”.

NOTE 3 In this document, percentages of gaseous components, contaminants and by-products, are always percentages per volume, measured at 20 °C, if not otherwise indicated.

NOTE 4 Reference is also made to CIGRE Brochure 802 [1]1.

NOTE 5 For further details on gases, e.g. ecotoxicology, also refer to the chemical database of the European Chemicals Agency, ECHA (www.echa.europa.eu), which takes the actual tonnage band into consideration.

NOTE 6 If gases for insulation and/or switching are regulated, their designation and regulation origin can be found in the IEC 62474 database (available at https://std.iec.ch/iec62474[26]).

NOTE 7 When reference to circuit-breakers is made, only gas circuit-breakers are of interest. When vacuum circuit-breakers are of interest, they are explicitly mentioned.