Miracle gas or not?
There are many published discussions and reports on various aspects of SF6 gas(sulphur hexafluoride) usage in electrical equipment. Most of them are based on facts and researches, but some are not.
34 Questions And Answers To Break the Myth About SF6 Gas In Electrical Equipment
Let’s try to answer the 34 questions and break the myth about this ‘miracle’ gas.
Note that most of answers are based on CAPIEL (Coordinating Committee for the Associations of Manufacturers of Industrial Electrical Switchgear and Controlgear in the European Union) researches and related IEC standards as well.
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11. What are the main commitments of the voluntary actions/agreements of manufacturers and users concerning SF6 handling?
Both, switchgear manufacturers and users are committed to a continuous improvement in reduction of emission rates as well as monitoring and annual reporting.
12. How is the effectiveness of voluntary actions verified?
The production processes of MV and HV switchgear in Western Europe have been improved so to reduce the specific emission rates of about 2/3 from1995 to 2003. Ecofys (*) determined for the same period an emission reduction of 40 %.
This improvement is substantiated by systematic application of comprehensive monitoring methodologies and intensive personnel training. According to the study already 70 % of potential measures are realised.
(*) ECOFYS, Sina Wartmann, Dr. Jochen Harnisch, June 2005, “Reductions of SF6 Emissions from High and Medium Voltage Equipment in Europe”
13. What are the user’s obligations for monitoring SF6 data of medium voltage switchgear?
As far as sealed pressure systems (sealed for life) are concerned the users do not normally need to either monitor or report emissions.
Therefore they only have to assure that the disposal and the end of life is carried out by a qualified entity, in accordance with available national rules.
14. How is the proper end-of-life treatment of SF6-switchgear ensured?
Following internationally acknowledged instructions (i.e. according to IEC 601634, CIGRE 2003 SF6 Recycling Guide).
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15. What are the user’s obligations when taking SF6-switchgear out of service?
To make sure that the SF6 is handled by a qualified entity or by qualified personnel according to IEC 61634 subclause 4.3.1. and according to IEC 60480 subclause 10.3.1.
16. How is used SF6-gas treated or disposed?
It is normally re-used after proper filtering. In some special cases disposal of the gas is necessary.
Appropriate detailed information can be found in IEC 61634 (handling SF6), IEC 60480 (used SF6); CIGRE guide for the preparation of customised “Practical SF6 Handling Instructions”.
17. In some European countries bans on SF6-switchgear have been proposed. Where are legal bans implemented?
There are no legal bans implemented. In political discussions reduced use of SF6 in some applications was proposed which are not related to the electrical industry.
In the past some proposals of this kind concerning electrical switchgear came up due to insufficient knowledge on how the electrical industry is using SF6. Once this was clarified and the benefits given by this technology were explained, the proposals were withdrawn.
18. Can we use vacuum as insulation medium?
Vacuum technology is already in use for switching purposes in the MV range. In the case of a small volume, a vacuum can be relatively easy maintained, which is essential to assure the performance of the switching device.
Application of vacuum as insulating medium in a larger volume is electro physically and technically much more demanding, economically exceeding difficult, and practically not realisable.
19. How can the user supervise the SF6 quality?
The sealed for life MV equipment does not require SF6 quality checks. For other HV equipment Annex B of IEC 60480 describes different methods of analysis applicable for closed pressure systems (on-site and in laboratory).
20. What about ageing process of SF6 gas? Is replenishment of gas needed after approximately 20 years?
It is generally not necessary because the gas quality than is in line with the values given in IEC 60480 Table 2 “Maximum acceptable impurity levels” (applicable for closed pressure systems). For MV sealed for life equipment no replenishment is necessary, because of the unique qualities of SF6 under normal operating conditions no degradation occurs.
To be continue...
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