Transactions of China Electrotechnical Society  2021, Vol. 36 Issue (17): 3572-3580    DOI: 10.19595/j.cnki.1000-6753.tces.201117
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Experimental Research and Simulation Analysis of Insulation Characteristics of C4F7N/CO2 Mixed Gas under Typical Clearance Structure
Xin Zhaozhao1, Jiang Xu2, Huo Peng2
1. Xi'an High Voltage Apparatus Research Institute Co. Ltd Xi'an 710077 China;
2. Xi'an XD Switchgear Electric Co. Ltd Xi'an 710077 China

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Abstract  

Eco-friendly C4F7N/CO2 mixed gas is one of the most potential substitutes for SF6 at present. In order to study the insulation characteristic of the C4F7N/CO2 mixed gas, and to search its matching relationship with the electric field under the typical clearance structure, the prototype was designed based on 72.5kV switch product including two kinds of electrode structures: disconnecting contact and coaxial electrode. The effects of different inflation pressures and different contact distances on the gas insulation performance under lightning impulse voltage was studied by experiments, and the electric field distribution changes under different clearance structures and different clearance distances were obtained through simulation calculation. Experimental and simulation results show that under the disconnecting contact structure and the coaxial electrode structure, 20%C4F7N+80%CO2 mixed gas with a gauge pressure of 0.4MPa and 16.7% C4F7N+83.3%CO2 mixed gas with a gauge pressure of 0.5MPa, of which the insulation strength can reach more than 80% of the pure SF6 gas insulation strength at the same pressure. Under the disconnecting contact structure, the clearance distance is 8mm, 246kV applied voltage (50% breakdown voltage at 0.4MPa), the highest electric field strength between clearances is 38.3kV/mm; under the coaxial electrode structure, the gap is 10mm, and the applied voltage is 228.5kV (50% breakdown voltage at 0.4MPa), the highest electric field strength between coaxial gaps is 26.8kV/mm. In order to achieve the insulation level of pure SF6 gas at a gauge pressure of 0.4MPa and a distance of 6mm, the pressure of the C4F7N/CO2 mixed gas can be increased to 0.5MPa or the contact distance can be increased to about 8mm. At the end of this article, the field strength design basis of C4F7N/CO2 mixed gas is discussed. The experimental research and simulation analysis in this article have verified the feasibility of C4F7N/CO2 mixed gas engineering application, Especially, it has guiding significance for the design of insulation structure when C4F7N/CO2 mixed gas is used in switchgear.

Key wordsC4F7N/CO2      insulation characteristics      typical clearance structure      simulation analysis     
Received: 28 August 2020     
PACS: TM213  
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Xin Zhaozhao
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Xin Zhaozhao,Jiang Xu,Huo Peng. Experimental Research and Simulation Analysis of Insulation Characteristics of C4F7N/CO2 Mixed Gas under Typical Clearance Structure[J]. Transactions of China Electrotechnical Society, 2021, 36(17): 3572-3580.
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https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.201117     OR     https://dgjsxb.ces-transaction.com/EN/Y2021/V36/I17/3572
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