Sulfur hexafluoride (SF6) is widely used in the power industry because of its excellent insulation and arc extinguishing performance. However, the high greenhouse effect of this material is being restricted by many countries around the world, thereby discouraging its usage. As a potential alternative to SF6, the compatibility of C5F10O with conductive copper materials used in electrical equipment is of great significance in ensuring the safe and stable operation of environmentally friendly gas-insulated equipment. In this paper, the interaction among C5F10O/N2, C5F10O/air gas mixture, and copper was studied via experiments and simulations. When the C5F10O/N2 (or air) gas mixture comes in contact with copper at the gas–solid interface, a small portion of C5F10O is decomposed to form C3F6 (or C3F6 and C3F6O) at high temperatures. Meanwhile, at low temperatures (120 °C), the C5F10O/air gas mixture becomes more compatible with copper than with the C5F10O/N2 gas mixture. When the experiment temperatures range between 170 °C and 220 °C, the compatibility of the C5F10O/air gas mixture with copper is significantly inferior to its compatibility with copper. Under high temperatures, the C5F10O/air gas mixture shows severe corrosion on the copper surface due to the presence of O2, forms a thick cubic grain, and emits irritating gases. The simulations show that the carbonyl group in C5F10O is chemically active and can be easily adsorbed on the copper surface. An anti-corrosion treatment must be performed on copper materials in manufacturing equipment. The findings provide an important reference for the application of C5F10O gas mixture.
This paper based on density functional theory (DFT) investigate the interaction of C5-PFK molecule with Cu ( 110) and (100) surfaces, in order to analyze the chemical compatibility of Cu metal in the environment of C5F10O (C5-PFK) insulation gas. The frontier molecular orbital theory implies that the C=O group in the C5-PFK molecule can interact strongly with the Cu surfaces. The results show that both Cu ( 110) and ( 100) surfaces have strong interactions with the C5-PFK molecule, showing chemisorption of the molecule, with Ead of -1.17 and -1.03 eV, respectively. Meanwhile, the C5-PFK molecule performs strong electron-accepting behavior in the interactions, which captures 0.262 and 0.204 e from the Cu ( 110) and ( 100) surface, respectively. Even though, the geometric and electronic properties of Cu surface are not largely impacted, as supported by the basically unchanged morphologies and DOS curves of Cu surfaces before and after gas adsorption. These findings manifest the favorable stability and compatibility of Cu metal in the C5-PFK environment. Our work uncovers the safe operation of C5-PFK immersed insulation devices with Cu-based generatrix and shell in a long running, which is of great significance to guarantee the safe operation of the power system.
The on-site measurement of transient voltages is of great significance in analyzing the fault cause of power systems and optimizing the insulation coordination of power equipment. Conventional voltage transformers normally have a narrow bandwidth and are unable to accurately measure various transient voltages in power systems. In this paper, a wideband parallel resistive–capacitive voltage divider is developed, which can be used for online monitoring of transient voltages in a 220 kV power grid. The structures of the high-voltage and low-voltage arms were designed. The internal electric field distribution of the high-voltage arm was analyzed. The influence factors and improvement techniques of the upper frequency limit were studied. The parameters of the elements of the divider were determined. The voltage withstand performances and scale factors under lightning impulses and AC and DC voltages, the temperature stabilities of scale factors and the step response and bandwidth of the developed voltage divider were tested. The results show that the deviations of the scale factors under various voltage waveforms and different temperatures ranging from −20 to 40 °C are within 3%. The withstand voltage meets the relevant requirements specified in IEC60071-1-2011. The step response 10~90% rise time is approximately 29 ns, and the 3 dB bandwidth covers the range of DC to 10 MHz.
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