Dengming Xiao

By Dengming Xiao

Part of the book: Applications of Monte Carlo Method in Science and Engineering

By Dengming Xiao

The research situation of environmentally friendly gas insulation is expounded in this paper. The basic physical and chemical properties of the insulating gases are analysed, to propose several environment-friendly insulating gas of potential alternative to sulphur hexafluoride (SF6). The insulation characteristics of different components gas mixtures with 90% of nitrogen (N2) and carbon dioxide (CO2) as buffer gas and 10% octafluorocyclobutane (c-C4F8), Trifluoroiodomethane (CF3I) and heptafluorobutyronitrile (C4F7N) as the main insulating gas had been tested with 5–20 mm sphere-plane electrode gaps in non-uniform electric field under the power frequency voltage and positive and negative lightning impulse breakdown. The development prospects of environmentally friendly gas insulation are forecasted. Further analysis of c-C4F8,CF3I and C4F7N (some friendly gases, which have the potential to replace SF6) are conducted trying to points out the further research direction.

Part of the book: Simulation and Modelling of Electrical Insulation Weaknesses in Electrical Equipment

By Dengming Xiao

Many researches of trifluoroiodomethane (CF3I) have shown that CF3I has many excellent properties that make it one of the possible alternatives of SF6. This paper reveals the effect laws of CF3I gas content, gap distance, gas pressure, polarity, and electric field nonuniform coefficient on the insulation performance of CF3I gas mixtures. In general, CF3I-N2 gas mixtures present a superior dielectric strength than CF3I-CO2 under different electric field sets. The experimental results indicate that 20 and 30% content CF3I-N2 gas mixtures can achieve nearly 50 and 55% insulation strength of pure SF6. In addition, to evaluate the arc interruption performance of environmentally friendly gas CF3I, we set up a CF3I transient nozzle arc model to study its thermodynamic and transport property. The analysis shows that CF3I gas has a good arc interruption capability, which mainly functions thermodynamic and transport properties approach that of SF6, and some are even better than SF6. The decomposition process is also aggravated by impurities including metal and water. The main by-products are greenhouse gases with GWP below that of SF6 and are lowly toxic and incombustible.

Part of the book: New Trends in High Voltage Engineering

By Su Zhao and Dengming Xiao

Synergetic effect is a special gas discharge phenomenon among insulating gas mixtures, which has important reference value for gas selection of future gas-insulated power equipment. The research progress and investigation methods of synergistic effect and insulation characteristics of different gas mixtures at home and abroad are reviewed in this chapter. The synergistic effect between different kinds of gas mixtures including SF6 gas mixtures and some new insulation gases such as c-C4F8, CF3I, and C4F7N is presented. Combined with the results of multiple studies, it can be seen that the synergistic effect of the gas mixture has a certain relationship with the electronic transport parameters and discharge patterns. Besides, the synergistic effect of the same gas mixture may change with the change of external conditions such as gas pressure, voltage type, and electrode distance.

Part of the book: Modern Applications of Electrostatics and Dielectrics