CF_3I在微水条件下的放电分解组分研究

Investigation Towards the Influence of Trace Water on CF_3I Decomposition Components Under Discharge

CF_3I可以作为SF6的替代气体而应用于各类气体绝缘设备中,而H_2O对CF_3I放电分解组分的影响还鲜有研究。故通过密度泛函理论(DFT),对处于常温常压下含有微量水分的CF_3I放电分解过程进行仿真分析,以求完善CF_3I的替代理论。首先,根据热力学理论求得CF_3I等主要分子的结构模型,并在此模型的基础上计算各个CF_3I分解反应进行的难易程度,获得CF_3I分子最可能的分解途径,并得到纯CF_3I气体的动态平衡过程;其次分析H_2O在放电环境下生成OH·和H·的反应路径;最后探讨在微水的影响下,CF_3I与H_2O在放电过程中可能发生的主要反应及产生的主要产物。研究结果表明:CF_3I直接吸附电子后分解成CF_3·和I-所需吸收的能量是最少的,因此该途径最为可行;H_2O分解产生H·和OH·最少,分别需要吸收377.58 k J/mol和488.29 k J/mol;微水的存在使得分解组分多样化和复杂化,破坏了CF_3I自身的动态平衡,由此降低CF_3I气体的局部放电起始电压进而减弱了其绝缘性能。

CF3I can be used in different kinds of gas insulation equipment as a substitute of SF6, while influence of H20 on CFaI decomposition components under discharge is rarely studied. Because of the substitution of CFaI on SF6, we adopted the density fimctional theory （DFT） to simulate the discharge decomposition process of CFaI in the presence of trace moisture under normal pressure and temperature （NTP） so as to perfect the substitute theory of CF3I. First, the structure of main molecules like CFaI was obtained through thermodynamics calculation. And on the basis of these mod- els, the most possible decomposition pathway and the process of dynamic balance of pure CFaI were calculated. Second, the reaction paths of H20 under discharge to generate OH ~ and H ~ were analyzed. Finally, under the influence of trace moisture, the main reactions and products of CF3I and H20 trader discharge were discussed. The results of research show that CF3I absorbing electrons directly to decompose into CF3 ~ and I- consumes minimum energy among four decomposi- tion pathways of CF31 molecules. So this pathway is most reasonable. The decomposition of HzO into H2 and OH2 needs 377.58 k J/tool and 488.29 kJ/mol at least, respectively. The existence of moisture causes various and complex de- composition components, damages the dynamic balance of CF3I, decreases the partial discharge initial voltage of CF3I gas, and destroys its insulation performance.