外电场对HFO-1234ze(E)分子的结构和性质的影响

Effect of External Electric Fields on the Structure and Properties of HFO-1234ze(E)

初步研究表明,HFO–1234ze(E)具有良好的绝缘性能和环保性能,有潜力作为绝缘介质应用于电气设备中。考虑到气体绝缘介质在设备中应用时处于外加电场作用下,然而目前尚无关于HFO–1234ze(E)气体特性受电场影响的研究。因此,通过理论计算获取了电场对HFO–1234ze(E)的分子结构和性质参数的影响规律,剖析不同电场作用下HFO–1234ze(E)微观特性的变化,从而揭示其具有良好绝缘性能的本质。计算结果显示HFO–1234ze(E)分子结构中除C—H键外其余键长存在明显变化,SF_(6)分子中仅沿电场方向的S—F键存在变化。HFO–1234ze(E)的能隙值随外电场增大而减小,电子跃迁更容易发生,分子结构化学稳定性降低,且C=C双键附近的电荷密度较大,具有较强的化学反应活性;同时HFO–1234ze(E)的能隙值整体小于SF_(6)的分子轨道能隙值,表明其分子结构化学稳定性略弱于SF_(6)。分子的结构变化会导致分子的性质改变,且气体的介电强度与分子的极化率和电离能存在紧密联系,与SF_(6)对比,HFO–1234ze(E)分子的电离能略低于SF_(6)的电离能,但极化率明显高于SF_(6),同时根据工频击穿实验结果,气压为0.1~0.3 MPa范围内时纯HFO–1234ze(E)的击穿电压为SF_(6)的0.78~0.89,具备较好的绝缘性能。

Previous studies show that HFO-1234ze(E)has good insulating properties and environmental protection properties,which has the potential to be used as an insulating medium in electrical equipment.The gas insulating medium is worked in the equipment under an external electric field and there is no research on the influence of the external electric field on the gas properties of HFO–1234ze(E).Therefore,in this paper,the influence law of electric field on the molecular structure and property parameters of HFO–1234ze(E)is obtained through theoretical calculations.Then,the changes in the microscopic properties of HFO–1234ze(E)under different electric fields are analyzed.Finally,the essence of its good insulating properties is revealed.The calculation results show that there are obvious changes in the other bond lengths except for the C—H bonds in HFO–1234ze(E).In SF_(6),there is only the chemical bond S-F along the electric field changes.The energy gap of HFO–1234ze(E)decreases with the increase of the external electric field,and the electronic transition is more likely to occur and the chemical stability of the molecular decreases.The charge density near the C=C double bond is large,which has a strong chemical reaction.At the same time,the energy gap of HFO–1234ze(E)is generally smaller than that of SF_(6),indicating that its molecular structure and chemical stability are slightly weaker than those of SF_(6).The changes in the structure of molecules lead to changes in its properties,and the dielectric strength of gas is closely related to the polarizability and ionization energy of molecules.In this paper,the ionization energy is slightly lower than that of SF_(6) and the polarizability of HFO–1234ze(E)is significantly higher than that of SF_(6) under different applied electric fields.At the same time,according to the power frequency test results,the breakdown voltage of HFO–1234ze(E)is 0.78~0.89 of that of SF_(6) with the gas pressure in 0.1~0.3 MPa,which has good insulating properties.