IEC 60376-2005 pdf – Specification of technical grade sulfur hexafluoride (SF 6 ) for use in electrical equipment.
1 Scope This International Standard defines the quality requirements and properties for technical grade sulfur hexafluoride (SF 6 ) for use in electrical equipment. It covers the properties and methods of test applicable to SF 6 when this substance is supplied for use in connection with any electrical equipment. NOTE Throughout this standard, the term SF 6 stands for technical grade sulfur hexafluoride. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60050(191), International Electrotechnical Vocabulary (IEV) – Chapter 191: Dependability and quality of service IEC 60050(212), International Electrotechnical Vocabulary (IEV) – Chapter 212: Insulating solids, liquids and gases IEC 60050(441), International Electrotechnical Vocabulary (IEV) – Chapter 441: Switchgear, controlgear and fuses IEC 60050(826), International Electrotechnical Vocabulary (IEV) – Chapter 826: Electrical installations IEC 60480, Guidelines for the checking and treatment of sulfur hexafluoride (SF 6 ) taken from electrical equipment and specification for its re-use IEC 61634, High-voltage switchgear and controlgear – Use and handling of sulfur hexafluoride (SF 6 ) in high-voltage switchgear and controlgear ISO 14040, Environmental management – Life cycle assessment – Principles and framework 3 Terms and definitions For the purposes of this document, the terms and definitions of IEC 60050(191), IEC 60050(212), IEC 60050(441) and IEC 60050(826) apply. Some of the more important ones are listed here for easy reference.
3.1 electrical equipment item used for such purposes as generation, conversion, transmission, distribution or utilization of electrical energy, such as electric machines, transformers, switchgear and controlgear, measuring instruments, protective devices, wiring systems, current-using equipment [IEV 826-16-01] 3.2 technical grade SF 6 SF 6 gas having a very low level of impurities in accordance with Table 1 3.3 container any kind of cylinder suitable for pressurized SF 6 NOTE This general term will be used throughout the text. 4 General properties of SF 6 Sulfur hexafluoride is a compound having the formula SF 6 . At normal room temperatures and pressures (20 °C and 100 kPa)  1 it is gaseous and has a density of 6,07 kg/m 3 (about five times the density of air). Since its critical temperature is 45,54 °C, it can be liquefied by compression . The pressure/temperature/density curves are given in IEC 61634. SF 6 is colourless, odourless and non-toxic. It is normally transported as a liquefied gas in containers Caution Although the gas is non-toxic, it will not support life, and equipment containing sulfur hexafluoride must not be entered without adequate ventilation. Similarly, since the gas has a much greater density than air, low lying areas, e.g. trenches, may contain high concentrations of the gas and the necessary precautions shall be taken to avoid asphyxiation. SF 6 is used in electrical equipment for the transmission and distribution of electricity (gas insulated substations, ring main units, circuit breakers, transformers, cables, etc.). It is also used for non-electric purposes, such as metallurgy, electronics, scientific equipment, etc.
4.2 Compatibility Technical grade sulphur hexafluoride is chemically inert and thermally stable  at normal temperatures. At temperatures up to about 180 °C the gas has a compatibility with metals used in electrical construction, similar to that of nitrogen. Operation at higher temperatures is possible, but SF 6 can decompose in these conditions, particularly in the presence of catalytic material and the by-products may be incompatible with some constructional materials. Individual cases need to be assessed separately. 5 Maximum acceptable impurity levels for technical grade SF 6 The available commercial gas contains impurities. The maximum impurity levels present in sulfur hexafluoride referred to in this standard as technical grade sulfur hexafluoride are given in Table 1. This table also lists appropriate analytical methods for the determination of impurity levels and the corresponding acceptable accuracy of measurement. NOTE Further handling and storage of the gas and operation of equipment may introduce additional quantities of impurities. This situation is covered in IEC 60480.