考虑介质介电驰豫影响时瞬态电场计算的时域有限元法  

Time-Domain Finite Element Method for Calculation of Transient Electric Field in Combined Insulating Structures Considering the Influence of Dielectric Relaxation

作　　者：文腾 崔翔 李学宝 刘思佳 赵志斌 Wen Teng;Cui Xiang;Li Xuebao;Liu Sijia;Zhao Zhibin(State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources,North China Electric Power University,Beijing 102206,China)

机构地区：[1]新能源电力系统国家重点实验室(华北电力大学),北京102206

出　　处：《电工技术学报》2022年第7期1735-1745,共11页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金委员会-国家电网公司智能电网联合基金资助项目(U1766219)。

摘　　要：在电力装备的实际运行过程中,可能遭受诸如操作冲击电压、雷电冲击电压等瞬态电压激励的作用。此外,随着电力电子器件在直流输电装备中的大规模应用,装备内部器件的绝缘结构承受的电压不再是传统的交流电压或直流电压,而是正极性重复性方波电压。为了研究这些装备或器件内的绝缘结构在瞬态电压激励下的电场特性,需要在电准静态场下计算其瞬态电场分布。在交变电场中,绝缘材料具有介电弛豫现象,其介电常数在频域上为频变函数。由于瞬态电压激励时间短、变化快,对应的频谱宽。因而,瞬态电压激励下的瞬态电场计算需要考虑材料的介电弛豫特性。为此,该文提出了考虑介质介电弛豫过程的时域有限元法。首先,将材料的介电弛豫现象用时变的介电参数表征,对含时变介电参数的电准静态场控制方程进行时空离散,推导了时域有限元方程和边界电场约束方程;然后,通过对比PEEK材料极化电流的实验测量结果与计算结果,验证了所提方法的有效性;最后,分析了瞬态电压激励下考虑材料介电弛豫特性的复合绝缘结构的瞬态电场分布特性。In the actual operation of electric power equipment,it may be subjected to transient voltage excitations such as switching surge voltage,lightning impulse voltage and so on.In addition,with the widespread application of power electronic devices in DC power transmission equipment,the voltage that the insulation structure of the internal devices bears is not traditional AC voltage or DC voltage,but positive repetitive square wave voltage.In order to study the electric field characteristics of the insulating structure in these equipment or devices under transient voltage excitation,it is necessary to calculate the transient electric field distribution under the electro-quasistatic field.Insulating materials exhibit dielectric relaxation phenomenon in the alternating electric field,and their permittivity is a frequency-dependent function in the frequency domain.Due to the short duration time and rapid change of the transient voltage,the corresponding frequency spectrum is wide.Therefore,the calculation of the transient electric field under transient voltage excitation needs to consider the dielectric relaxation characteristics.For this reason,this paper proposes a time-domain finite element method which considers the dielectric relaxation process of the materials.In this paper,the dielectric relaxation phenomenon of the material is characterized by the time-varying permittivity.The governing equation is discretized in time and space.The time-domain finite element equation and the constrained electric field equation on the boundary are derived.Then,the effectiveness of the calculation method proposed in this paper is verified by comparing the experimental results and calculation results of the polarization current of PEEK material under the step voltage.Finally,the distribution characteristics of the transient electric field of the combined insulating structure considering the dielectric relaxation characteristics of the material under transient voltage excitation are analyzed.

关 键 词：介电弛豫 频变 时域有限元法 边界电场约束方程 电准静态场 

分 类 号：TM211[一般工业技术—材料科学与工程]