Breakdown Characteristics of SF6 and Liquefied SF6 at Decreased Temperature

• Choi, Eun-Hyeok ;
• Kim, Ki-Chai ;
• Lee, Kwang-Sik
• Accepted : 2012.06.08
• Published : 2012.09.01
• 46 7

Abstract

$SF_6$ gas has been used as arc quenching and insulating medium for high and extra high voltage switching devices due to its high dielectric strength, its excellent arc-quenching capabilities, its high chemical stability and non toxicity. Despite of its significant contributions, the gas was classified as one of the greenhouse gas in the Kyoto Protocol. Thus, many researches are conducted to find out the replacement materials and to develop the $SF_6$ gas useless electrical equipment. This paper describes experiments on the temperature change-related breakdown characteristics of $SF_6$ gas ($SF_6$) and $SF_6$ liquid ($LSF_6$) in a model GIS(Gas-Insulated Switchgear) chamber in order to show the possibility of more stable and safe usages of $SF_6$ gas. The breakdown characteristics are classified into three stages, namely the gas stage of $SF_6$ according to Paschen's law, the coexisting stage of $SF_6$ gas with liquid in considerable deviation at lower temperature, and the stage of $LSF_6$ and remaining air. The result shows that the ability of the $LSF_6$ insulation is higher than the high-pressurized $SF_6$. Moreover, it reveals that the breakdown characteristics of $LSF_6$ are produced by bubble-formed $LSF_6$ evaporation and bubbles caused by high electric emission and the corona. In addition, the property of dielectric breakdown of $LSF_6$ is determined by electrode form, electrode arrangement, bubble formation and movement, arc extinguishing capacity of the media, difficulty in corona formation, and the distance between electrodes. The bubble formation and flow separation phenomena were identified for $LSF_6$. It provides fundamental data not only for $SF_6$ gas useless equipment but also for electric insulation design of high-temperature superconductor and cryogenic equipment machinery, which will be developed in future studies.

Keywords

$SF_6$ gas;$SF_6$ liquid;Breakdown characteristics

References

1. Landry, M. et al. "Dielectric withstand and breaking capacity of $SF_6$ circuit breakers at low temperatures" Power Delivery, IEEE Transactions on, pp. 1029-1035, July 1988
2. Gong Guoli et al, "The influence of $SF_6$ and $SF_6$/$N_2$ dissociating products on the electrical performance of several insulating varnishes", Electrical Insulating Materials, pp. 495-497, 1995
3. T.Ueda et al, "Discrimination of Partial Discharge Electromagnetic Signal in $SF_6$ Gas from External Noise Using Phase Gate Control Method", IEEE International Symposium on Electrical Insulation, pp. 117-120, 1996
4. Kwang-Sik Lee, "A Study on the discharge characteristics of liquid nitrogen at atmospheric pressure", KIEE Vol 45 No 7, 1996.7.
5. C.Beyer et al. "Influence Reactive $SF_X$ Gases on Electrode Surfaces after Electrical Discharge under $SF_6$ Atmosphere", IEEE Trans, pp. 234-240, 2000
6. Kwang-Sik Lee, "A Study on the Discharge Characteristics of Liquid Nitrogen and Gases at Very Low Temperature", KEPCO, 1993.8.
7. Kwang-Sik Lee, "The Characteristics of Insulation with Temperature Variations of $SF_6$" KIEE Vol 52C No 8, 2003.8
8. Kwang-Sik Lee, Eun-Hyeok Choi, "The Positive Effect and the Breakdown Characteristics in $SF_6$ and $LN_2$", KIEE Vol 54C No 8, 2005.8

Cited by

1. Surface Flashover Characteristics on Poor Contact in N2/O2Mixture Gas under Non-Uniform Field vol.29, pp.8, 2015, https://doi.org/10.5207/JIEIE.2015.29.8.063
2. Study on oxygen/nitrogen gas mixtures for the surface insulation performance in gas insulated switchgear vol.22, pp.3, 2015, https://doi.org/10.1109/TDEI.2015.7116352
3. Review of Insulation Performance in Synthetic Air and Dry Air for High Voltage Equipment in Distribution Class vol.29, pp.12, 2015, https://doi.org/10.5207/JIEIE.2015.29.12.033
4. On-line Temperature Monitoring of the GIS Contacts Based on Infrared Sensing Technology vol.9, pp.4, 2014, https://doi.org/10.5370/JEET.2014.9.4.1385
5. Effect of Decomposition Product on the Insulation Characteristics of Mineral Oil as Insulation Medium of Distribution Transformer vol.28, pp.6, 2014, https://doi.org/10.5207/JIEIE.2014.28.6.052
6. Analysis of Breakdown Voltage Dispersion and Breakdown Process in Mineral Oil vol.29, pp.6, 2015, https://doi.org/10.5207/JIEIE.2015.29.6.035

Acknowledgement

Supported by : Yeungnam University