Decomposition Properties of Trifluoroiodomethane Under Discharges and Interruptions

J Electr Eng Technol.2018; 13(6): 2385-2391 ISSN(Print) 1975-0102 http://doi.org/10.5370/JEET.2018.13.6.2385 ISSN(Online) 2093-7423

Decomposition Properties of Trifluoroiodomethane under Discharges and Interruptions

Fan-Yi Cai*, Dong-Xian Tan**, Bai-Jie Zhou*, Jian Xue* and Deng-Ming Xiao†

Abstract – This paper is devoted to detecting decomposition characteristics of Iodotrifluoromethane (CF3I) under alternating current (AC) discharges or load current interruptions. The decomposition products are measured utilizing chromatography-mass spectroscopy. It is found that less than 1% CF3I gas decomposed after several interruptions at load current of 200 A or hundred times of AC discharges. However, under interruptions at a current of 400 A, more than 95% CF3I gas decomposed into carbon tetrafluoride (CF4) and hexafluoroethane (C2F6). The equilibrium compositions based on Gibbs free energy minimization of CF3I was calculated to explain the decomposition mechanism.

Keywords: CF3I, Decomposition products, Interruption.

1. Introduction in the atmosphere for a short time, which leads a slight feature on environmental impact. Due to this, it is essential Due to excellent comprehensive qualities including to investigate the by-products of CF3I, particularly in terms insulating performance, arc-quenching capability, non- of discharges and interruptions.

toxic, non-flammable and thermal stable, SF6 (sulfur Donnelly and his co-works found that CF3I gas could hexafluoride) has been considered the most common remain stable after a 5-year ambient temperatures storage gaseous insulation or interrupting medium for high period from 1997-2002 [10]. M. S. Kamarudin discovered voltage power systems, such as transformers bushings, that solid by-product after more than 1400 times breakdown gas-insulated transmission lines (GIL), and gas-insulated tests [11] was iodine (I2). Moreover, the deposition of

switchgear (GIS) [1]. However, SF6 is a strong greenhouse iodine on the electrode affected insulation performance by gas with high global warming potential (GWP) of 23,500 more than 10%. Investigations on gaseous decomposition

[2]. Therefore, the usage of SF6 has been restricted on of CF3I after partial discharges (PD) and sparkovers have Kyoto Protocol [3] and the power industry has been been carried out by M. Jamil et al [12] and Takeda et al intensively searching for an environmentally friendly gas respectively [13]. In their measurements, C2F6, C2F4, CHF3,

to replace SF6 in a long time. C3F6, C3F8, and C2F5I were detected as gaseous by- In recent years, many scientists claimed that CF3I is a products. The dominant gaseous by-products were C2F6. Tu potential alternative gas to SF6 [4-7]. CF3I gas has superior et al also analyzed the gas discharge by-products of insulating performance and several other advantages of CF3I/Nitrogen (N2) gas mixtures at high-pressure [14]. physical and chemical properties. Specifically, it is a They found that the dominant gaseous by-products were colorless, odorless gas and has no damage to the ozone C2F5I and finally converted to I2 and CF3I. The formation

layer [8]. Compared to SF6, the major advantage of CF3I is mechanism of CF3I discharge components and effect of a very low GWP, which is about 1-5 times than that of trace water and oxygen on decomposition were studied

carbon dioxide (CO2). Thus, CF3I has been listed in the by Zhang et al [15, 16]. The results show that the potential environmentally friendly alternative refrigerant decomposition rate of CF3I was accelerated in the presence products catalog by United Nations Environment Programme of trace water and oxygen and some harmful gas such as [4, 9]. carbonyl fluoride (COF2) was produced.

The main reason for the low GWP value of CF3I is the Though there are many researches on the by-products of molecular structure and its relatively unstable chemical the substitute gas after discharges, reports the by-products properties. The solar radiation and even visible light can under interruptions are few, qualitative and lack of data. H. make the C-I bond breaking, which leads to the Katagiri found that CF3I decomposed significantly and

decomposition of CF3I molecule. So CF3I can only present the decomposition products contained solid iodine, which attached to the gas hose making it yellow after CF3I † Corresponding Author: Dept. of Electrical Engineering, Shanghai extinguishing capability test with large current arcs [7]. H. Jiao Tong University, China. ([email protected]) * NARI Group Corp., State Grid Electric Power Research Institute, Kasuya measured the decomposed gas density after current China. ([email protected]) interruptions with CF3I spectra, their results revealed that ** Dept. of Electrical Engineering, Shanghai Jiao Tong University, fluorine release from CF I was less than that from SF [17]. China. 3 6 Received: May 23, 2018; Accepted: August 27 2018 In this paper, the species and quantities of decomposition

2385 Copyright ⓒ The Korean Institute of Electrical Engineers This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Decomposition Properties of Trifluoroiodomethane under Discharges and Interruptions

products of CF3I after small current interruptions were was used to investigate the interruption characteristics. The tested by means of gas chromatography-mass spectrometer output current around 4~40 kA is provided by the LC (GC-MS). The arc experiments were carried out in an oscillation circuit. A 49.2 Hz output current was produced industrial load switch for SF6 gas and the gas chamber is by a 55,760 µF capacitor bank (Cs) and a 187.5 µH replaced with pure CF3I gas were experimentally verified. thyristor controlled air reactor (Ls). A 12 kV vacuum The by-products of CF3I after different times of AC circuit breaker with the spring operating mechanism was breakdown discharges were also detected as a reference. used as the main switch (MS) while a 40.5 kV vacuum The organization of this paper is as follows: Section 2 circuit breaker with the spring operating mechanism was specifically describes the materials for the tests, experimental used as the auxiliary switch (AB). Arc voltage and current setup and methodology. Interruption and decomposition were measured by the voltage transducer and the Rogowski results were demonstrated in Section 3. The proposed coil, respectively. Digital memory oscillograph was used to mechanism and the poison level of the by-products of CF3I record the experimental data. After the interruption is discussed in detail in Section 4. Section 5 concludes the experiment, we let the gases stand for 1 hour to ensure the paper. decomposition further mixed in the cavity and then sample the gases with vacuum sampling bags.

2. Materials and Methods 2.3 The AC breakdown measurement system for CF3I gas 2.1 Materials The by-products of CF3I under AC breakdown tests were

CF3I gas was supplied by Beijing Yuji Science and Technology Co., Ltd with purity surpass 99.5%. Main impurities are C3HF5 (1,1,3,3,3-Pentafluoro-1-propene), CHF3 (Trifluoromethane), C2HF5 (Pentafluoroethane) and C4F8 (Perfluoro-2-butene). Water (H2O) content of the gas was about 0.05 wv%.

2.2 The interruption measurement system for CF3I gas

The interruption tests of pure CF3I gas were carried out in a commercial SF6 arc quenching load switch (TO, Fig. 1). The rated normal current of the load switch is 630 A. Moreover, the filling pressure of the working chamber was 0.04 MPa. The sketch of the test circuit shown in Fig. 2

Fig. 2. Circuit used in the load current interruption experiments

Fig. 1. Schematic diagram (left part) and photograph (right part) of 12 kV load switch prototype filling with CF3I. ① busbar compartment, ② switch com- Fig. 3. Schematic diagram of the AC breakdown experi- partment, ③ control unit, ④ cable compartment mental apparatus

2386 │ J Electr Eng Technol.2018; 13(6): 2385-2391 Fan-Yi Cai, Dong-Xian Tan, Bai-Jie Zhou, Jian Xue and Deng-Ming Xiao also detected for comparison. The experimental setup was illustrated in Fig. 3. Tests were made between a stainless steel electrode and a horizontal plate electrode in a cylindrical closed chamber made of stainless steel. The diameter of the needle electrode was 1 mm and the diameter of the plate diameter was 400 mm. The discharge gap was 10 mm. Hence, the non-uniform coefficient of the electric field is 12.3. In addition, the observation window was set up to watch to watch the discharge path during breakdown tests. A 300 kV AC transformer was used in the AC withstand test. The rising rate of AC voltage was 1 kV/s, and it was increased continuously until the breakdown took place. AC withstand voltage was obtained from the average of 10 measurements by the voltage increasing method. There was 1 min interval between each discharge to ensure the gas can recovery the initial insulation conditions. In this paper, we detected the gases compositions of 5 sample groups include the origin gas and the gases after 0 to 500 times AC discharges.

2.4 Gaseous by-product measurement system for Fig. 4. Waveform of interruption experiments, (a) the load CF I 3 current is 200 A, (b) the load current is 400 A

Identifications of the products after the electrical tests were achieved by GC/MS (Agilent 7890A/5975C) system equipped with a CP-Pora PLOT Q column (30 m × 0.25 mm × 0.25 μm). The column was programmed as follows: the initial temperature was set at 60 °C for 6 min; then the temperature was increased at the rate of 40°C/min, and finally reached to 200°C and held for 11 min. The instrumental parameters were set up as follows: injection port temperature, 200 °C; TCD detector, 200 °C; the carrier gas rate, 4.1 ml He/min. The GC/MS features were identified by comparing the mass fragmentation patterns of the products with patterns from the built-in Wiley/NIST library. Fig. 5. GC-MS analysis of CF3I gas in different experimental conditions (from bottom to top). (a) Initial gas, (b) After 500 times AC breakdown tests, 3. Results (c) After successful interruption (200 A), (d) After failed interruption (400 A). The main detected 3.1 Interrupting capacity of CF3I gas under different substances are marked in the large image. The insert load currents picture shows several traces detected products (less than 500 ppm) with retention time from 2.8 to 10.0 In the interruption tests, the peaks of the main current minutes: 1. C2F4, 2. CHF3, 3. C2HF5, 4. C3F8, 5. were set at 200 A and 400 A. The experiment results of H2O, 6. C4F8, 7. C3HF5 interruption showed that CF3I gas can switch off current of 200 A, but could not switch off current of 400 A (Fig. 4). 3.2 Determination of the decomposition products Specifically, Fig. 4(a) shows a waveform of a successful under load current interruption and AC break- interruption at current of 200 A. The transient recovery down tests for CF3I gas voltage (TRV) was established at about 22 kV (50 Hz), while the total duration of the current was three half cycles We use GC-MS to measure the ingredients of CF3I gas of the sine wave (30 ms). Fig. 4(b) shows a waveform of a after interruption tests. GC-MS spectrogram changes of failure interruption at a current of 400 A. The time of CF3I gas in different experimental conditions were shown through-flow was about eight half-cycles of the sine wave in Fig. 5. Different molecules could be identified by (80 ms). The energy stored in the oscillation circuit was retention times and the mass fragmentation patterns (Table dissipated due to the arc burning continuously. 1). In initial state, there exist three prominent peaks for N2,

http://www.jeet.or.kr │ 2387 Decomposition Properties of Trifluoroiodomethane under Discharges and Interruptions

Table 1. GC-MS data of the by-products Under the conditions of high pressure, C2F5I produced during discharge after a certain period is converted to CF I Retention time 3 No. Sample Data of GC-MS (m/z) (min) and I2. Although there are several kinds of by-products, the + + + CF4 1.94 88, M; 69, CF3; 50, CF2 maximum content of these is about 3500 ppm while others + + + 138, M; CF3CF2; 69, CF3; 50, are less than 1000 ppm. That is to say, decomposition C2F6 2.55 + CF2 amount of CF3I in these situations is less than 1%. It is also C F 2.97 100, +M; 50, +CF 2 4 2 a reflection of the insulation stability of CF3I gas. But + + 169, CF3CF2CF2; 119, C2F5; 100, apparently, CF I gas could not fulfill the interruptions for C3F8 5.28 + + + + 3 CF2CF2; 69, F3C; 50, CF2; 31, FC 400 A in the load switch we used. Two distinct peaks of + + + CF3I 10.59 196, M; 127, I ; 69, F3C CF4 and C2F6 with much larger peak area than that of CF3I 246, +M; 227, +CF CFI; 127, +I; 119, C F I 12.33 3 could be observed in the GC-MS analysis (Fig. 5). The 2 5 +C F ; 100, +C F ; 69, +CF ; 50, +CF 2 5 2 4 3 2 abundance ratios of CF /CF I and C F /CF I are 8 and 9.5 4 3 2 6 3 respectively. In other words, more than 95% CF3I was already decomposed. Toxic decomposition products formation under arcing or discharge conditions might involve risks to the health of anyone in the immediate surroundings of electrical equipment filled, therefore the poison level of the

decomposition products of CF3I gas should be determined before application.

First, CF3I has a very low cardiac sensitization LOAEL (Lowest Observable Adverse Effect Level), a volume fraction of 0.4 %, although the acute 4-hour rat ALC (Approximate Lethal Concentration, essentially an LC50) is much higher.

C2F5I has toxicity higher than CF3I, but toxicity of these two alkyl iodides can be considered acceptable for Fig. 6. The intensity of by-products as a function of the insulation purposes [20]. The perfluorocarbons (PFCs) by-

times of AC breakdown tests. Additional data points products of CF3I are C2F6, CF4, C2F4 and C3F8. In fact, are the by-products under interruption these highly stable compounds have no measurable toxicity, they are widely used today in the semiconductor industry, CO2, CF3I and five tiny peaks for CHF3, C2HF5, H2O, C4F8, plasma chemistry and fire suppression [21]. While the and C3HF5. However, N2 and CO2 were detected because a addition of hydrogen increases toxicity, hydrofluorocarbons few amount of air mixed in sample gas during sample (HFCs) still generally have low toxicity. The main impurities introduction process. Moreover, it should be noted the kind of CF3I (CHF3, C2HF5, C3HF5) are allowable for use in of chromatogram column used in our GC-MS experiments normally occupied areas [22]. In summary, the toxicity of could not catch oxygen signal. Other components were the decomposition of CF3I we detected is relatively low and it known impurity during CF3I producing process [18, 19]. is surely up to toxicity standards in equipment. Compared with initial gas as reference, the results reveal that C2F6, tetrafluoroethane (C2F4) octafluoropropane (C3F8), pentafluoroethyliodide (C2F5I) were the gaseous 4. Discussion by-products of CF3I under AC breakdown tests or the interruptions at current of 200 A. However, when the current The composition of CF3I (Fig. 7) was calculated with the increase to 400 A, more than 95% CF3I was thoroughly minimization of the Gibbs free energy method [23] to decomposed. Thus C2F6, CF4 became the primary products. determining the chemical state of CF3I gas. The specific By analyzing the relative peak intensities, we can see the calculation steps of the calculation were presented in proportion change of by-products in different experimental previous literature [23, 24]. The so-called Newton-Raphson conditions. As shown in Fig. 6, the content of C2F6, C2F5I, C2F4 and C3F8 keep increasing with AC breakdown times. Table 2. Species in the calculation of the compositions of The amounts of other components, including CHF , C HF , 3 2 5 the CF3I gas C3HF5, C4F8 and H2O, remain stable after AC breakdown tests. Thus, these gases could be thought as the inherent Classification Species Neutral CF I, C F , C F , C F , C F , C F , CF , IF, C , impurities rather than the decomposition products. The 3 3 6 3 8 2 6 2 4 2 2 4 2 molecules C3, C4, C5, F2, I2; intensity of C2F6 was approximately equal for interruption Radical C, F, I, CF3, CF2, CF, C2F5; at 200 A and AC breakdown tests. The amount of C F CF3+, CF2+, C+, C2+, C-, C2+, C2−, F+, F2+, F+, F2+, 3 8 Ions increased slightly while the opposite happened to the I+, I−； Electron e amount of C2F5I, which is consistent with reference [14].

2388 │ J Electr Eng Technol.2018; 13(6): 2385-2391 Fan-Yi Cai, Dong-Xian Tan, Bai-Jie Zhou, Jian Xue and Deng-Ming Xiao

According to the experimental results, CF3I gas can remain stable after ac breakdown test and interruption of load current at 200 A. However, when the given energy is large

enough (interruption of load current at 400 A), CF3I gas will decompose completely.

5. Conclusion

The dissociation behaviors of CF3I gas under load current interruption were studied with a commercial SF6- filled arc quenching load switch. And the by-products of

CF3I after several hundred times of AC breakdown discharges in the self-made cavity were also detected as a

Fig. 7. Equilibrium composition of CF3I plasma as a reference. function of temperature at 1 atm. The decomposition properties of CF3I were dramatically different under different load current interruption. It concretely embodies in the components and contents of by-products. Under AC discharges and successful arc

extinguishment at a current of 200 A, less than 1% CF3I is decomposed. The dominant by-product is C2F6 and a small amount of C2F4, C3F8 and C2F5I, which is the same as by- products after the AC breakdown discharges. The maximum content of these gases is about 3500 ppm while others are less than 1000 ppm. However, under the interruption at a

current of 400 A, almost 95% CF3I gas is decomposed. The primary decomposition products are C2F6 and CF4. All of the detected products are weakly toxic. We also discuss the mechanism of the decomposition

process though the calculation of equilibrium CF3I arc plasma. CF3I gas can hardly recover once the decomposition process occurred. However, further investigations Fig. 8. The calculated mole content changes of CF3I with on the temperature profile of the formed plasma and its increase in temperatures from 100 to 6000 K and relationship with the energy should be carried out. the pressures from 1 to 6 atm method was applied to solve the equations. A total of 35 Acknowledgements species in gas phase were took account in the calculation (Table 2): All of the thermodynamic properties of the This work was supported by Science and Technology species were obtained from NIST Kinetics Database [25]. Project of SGCC (Research on SF6 Alternative Gas for The pressure of the system was 1 to 6 atm, while the Insulation and Arc Quenching Application). temperature ranged from 100- 6000 K (Fig. 8). When the temperature is above 6000 K, the gas consists of F, C, CF, C+, I–, I and the electron. Between1000 K to References

5000 K, CF4, CF2, I have much higher concentrations than other species. While the temperature is 300-400 K, CF4, I2 [1] L. G. Christophorou and R. J. Vanbrunt, “SF6/N2 and C2F6 are the primary product. Nevertheless, the content Mixtures - Basic and HV Insulation Properties,” of C3F8 much less than the experiment results. Because IEEE Trans. Dielectr. Electr. Insul., vol. 2, pp. 952- the formation of C3F8 need to go through a transition 1003, 1995. state, which demands higher activation energy than the [2] J. Reilly, R. Prinn, J. Harnisch, J. Fitzmaurice, H. radical coupling steps such as the formation process of Jacoby, D. Kicklighter, et al., “Multi-gas assessment

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http://www.jeet.or.kr │ 2389 Decomposition Properties of Trifluoroiodomethane under Discharges and Interruptions

[4] Y. Yokomizu, M. Suzuki, and T. Matsumura, discharge components and effect of oxygen on “Thermodynamic, transport and radiation properties decomposition,” Journal of Physics D-Applied Physics, of high-temperature CF3I and transient conductance vol. 50, Apr 2017. of residual arc sustained in axial CF3I flow,” IEEJ [17] H. Kasuya, Y. Kawamura, H. Mizoguchi, and e. al, Trans. Electr. Electron. Eng., vol. 1, pp. 268-275, “Interruption capability and decomposed gas density 2006. of CF3I as a substitute for SF6 gas,” IEEE Trans. [5] X. Zhang, S. Tian, S. Xiao, Y. Li, Z. Deng, and J. Dielectr. Electr. Insul., vol. 17, pp. 1196-1203, 2010. Tang, “Experimental studies on the power-frequency [18] Y. Hu, T. Wu, W. Liu, L. Zhang, and R. Pan, “CF3I breakdown voltage of CF3I/N2/CO2 gas mixture,” Synthesis Catalyzed by Activated Carbon: A Density Journal of Applied Physics, vol. 121, p. 103303, 2017. Functional Theory Study,” The Journal of Physical [6] X. Zhao, J. Jiao, and D. Xiao, “Breakdown Electric Chemistry A, vol. 118, pp. 1918-1926, 2014. Field of Hot 30% CF3I/CO2 Mixtures at Temperature [19] G.-C. Yang, S. Lei, R.-M. Pan, and H.-D. Quan, of 300–3500 K During Arc Extinction Process,” “Investigation of CF2 carbene on the surface of acti- Plasma Science and Technology, vol. 18, p. 1095, vated charcoal in the synthesis of trifluoroiodomethane 2016. via vapor-phase catalytic reaction,” Journal of [7] H. Katagiri, H. Kasuya, H. Mizoguchi, and S. Fluorine Chemistry, vol. 130, pp. 231-235, 2009. Yanabu, “Investigation of the performance of CF3I [20] NFPA 2001 Standard on Clean Agent Fire Gas as a Possible Substitute for SF6,” IEEE Extinguishing Systems, 1996 Edition, National Fire Transactions on Dielectrics and Electrical Insulation, Protection Association, Quincy, MA, 1996. vol. 15, pp. 1424-1429, 2008. [21] Ledbetter, A., “Acute Inhalation Toxicity Study of [8] S. Solomon, J. B. Burkholder, A. R. Ravishankara, Iodotrifluoromethane in Rats”, Final Report Project and R. R. Garcia, “Ozone depletion and global No. 1530-001; Study No. 2, ManTech Environmental warming potentials of CF3I,” Journal of Geophysical Technology, Research Triangle Park, North Carolina, Research: Atmospheres, vol. 99, pp. 20929-20935, Center for Global Environmental Technologies, 1994. University of New Mexico, Albuquerque, New [9] Y.-Y. Duan, M.-S. Zhu, and L.-Z. Han, “Experi- Mexico, 1994. mental vapor pressure data and a vapor pressure [22] NFPA 2001 Standard on Clean Agent Fire equation for trifluoroiodomethane (CF3I),” Fluid Extinguishing Systems, 2000 Edition, National Fire Phase Equilibria, vol. 121, pp. 227-234, 1996. Protection Association, Quincy, Massachusetts, 2000. [10] M. K. Donnelly, R. H. H. Jr., and J. C. Yang, “CF3I [23] Q. Gao, A. Yang, X. Wang, A. B. Murphy, Y. Li, C. Stability Under Storage,” Technical Note (NIST TN), Zhang, et al., “Determination of the Dominant NIST Pubs 2004. Species and Reactions in Non-equilibrium CO2 [11] M. Kamarudin, “ Experimental investigation of CF3I- Thermal Plasmas with a Two-Temperature Chemical CO2 gas mixtures on the breakdown characteristics in Kinetic Model,” Plasma Chemistry and Plasma uniform and nonuniform field configurations “ PhD, Processing, vol. 36, pp. 1301-1323, 2016. Engineering, Cardiff University, 2013. [24] X. Wang, L. Zhong, M. Rong, A. Yang, D. Liu, Y. [12] M. K. Mohd Jamil, S. Ohtsuka, M. Hikita, H. Saitoh, Wu, et al., “Dielectric breakdown properties of hot and M. Sakaki, “Gas by-products of CF3I under AC SF6 gas contaminated by copper at temperatures of partial discharge,” Journal of Electrostatics, vol. 69, 300-3500 K,” Journal of Physics D: Applied Physics, pp. 611-617, 2011. vol. 48, p. 155205, 2015. [13] T. Takeda, S. Matsuoka, A. Kumada, and e. al, [25] NIST Computational Chemistry Comparison and “Sparkover characteristics in CF3I gas and CF3I/N2 Benchmark Database, [Online]. Available: gas mixture under non-uniform field gaps,” IEEJ http://cccbdb.nist.gov/. Transactions on Power and Energy, vol. 130, pp. 813-818, 2010. [14] Y. p. Tu, F. w. Zhou, C. Wang, S. c. Qin, and Y. Luo, “Discharge breakdown by-products of CF3I/N2 gas Fan-Yi Cai He received Ph.D. degree mixtures at high pressure,” in 2016 IEEE Electrical in natural science chemistry from the Insulation Conference (EIC), 2016, pp. 301-304. University of Science and Technology [15] X. Zhang, S. Xiao, J. Zhang, C. Li, Q. Dai, and Y. of China in 2014. He is with the Han, “Influence of humidity on the decomposition Electrification Equipment Bussiness products and insulating characteristics of CF3I,” Unit of Nari Group Corporation as a IEEE Trans. Dielectr. Electr. Insul., vol. 23, pp. 819- R&D Engineer for the benign solid 828, 2016. insulated materials and SF6 alternatives [16] S. Xiao, Y. Li, X. X. Zhang, J. Tang, S. S. Tian, gas in high voltage equipment. and Z. T. Deng, “Formation mechanism of CF3I

2390 │ J Electr Eng Technol.2018; 13(6): 2385-2391 Fan-Yi Cai, Dong-Xian Tan, Bai-Jie Zhou, Jian Xue and Deng-Ming Xiao

Dong-Xian Tan He received the M.Sc. degree from Shenyang University of Technology, China in 2006, currently he is studying for the Ph.D. degree in department of electrical engineering of Shanghai Jiaotong University, China. From 2013, he works as chief engineer and deputy general manager of Shanghai ROX electric Co., Ltd. He is working on the development of solid insulated and green-gas insulated switchgears, and failure analysis of electrical insulation of high voltage equipments.

Bai-Jie Zhou He received the Ph.D. degree from Nanjing University, China in 2011. Currently he works as product engineer and project manager of Smart Electrification Equipment Bussiness Unit in Nari Group Co., Ltd. He is working on the development of eco- friendly solid and gas insulation material.

Jian Xue He received the Ph.D. degree from Nanjing University, China in 2014, currently he works as engineer in Nari Group Co., Ltd. He is working on the development of solid insulated and green-gas insulated switchgears, and failure analysis of electrical insulation of high voltage equipment.

Deng-Ming Xiao He was born in Guangxi Province, China in 1953. He received the Ph.D. degree from the School of Electrical Engineering, Xi’an Jiaotong University, China, in 1994. Currently, he is a Professor with the Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai, China. He has worked on gas insulation system, electrical- equipment online monitoring, and fault diagnosis for more than 20 years.

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