变压器油的击穿特性与流注放电过程的数值模拟

发布时间：2018-04-22 22:41

本文选题：流注放电 + 变压器油　；参考：《东北电力大学》2017年硕士论文

【摘要】：在变压器的日常运行中,其最重要的内绝缘介质是变压器油,由此可见变压器油在保障电力系统的稳定运行中扮演着至关重要的作用。因此,其绝缘性能的好坏直接影响到电网能否稳定运行。人们研究变压器油中放电理论基本上都是从研究带电粒子在电场中的运动规律及推广应用方面入手。无论是实验研究或是理论探讨油中放电的原理过程,分析不同的条件或是电极系统下的液体放电规律,进而保障各类电力设备能够稳定安全地运行都有十分重要的研究价值和应用意义。目前,在研究变压器油中放电现象的过程中,经过大量的研究工作与试验,现已取得了丰硕的成果。本文在参考和比较国内外一系列变压器油中放电理论和试验成果的同时,由基础物理过程定律入手,构建了变压器油流注放电发展过程的物理模型,包括电极结构以及仿真计算区域。在变压器油流注放电的发展过程中,影响其发展的物理过程的因素主要有两方面,一方面是带电粒子在电场中的运动过程,另一方面是空间电荷对电场的影响。经过实践对比和大量参考文献的查阅,确定了切实可行的带电粒子连续性方程,以及反应带电粒子对电场影响的空间泊松方程。同时,在查阅许多相关文献之后,找出了由国内外学者从变压器油流注放电试验中获取到的经验公式计算出来的变压器油流注放电仿真的输运和反应系数。之后,分别考量物理模型、带电粒子连续性方程以及空间泊松方程的不同条件,确定了相应的边界条件和参数选择。考虑到在带电粒子的连续性方程的求解过程中,其对流项是远远大于扩散项的,因此适当引入了人工扩散项用来抑制求解过程的数值振荡问题。通过对空间电荷在变压器油中的产生与消失机理的研究,确定了其在带电粒子连续性方程中的表达式,进而明确了场致电离为影响流注放电发展过程的主要电离机制。采用COMSOL Multiphysics仿真软件进行变压器油中流注放电数值模拟,建立相应的二维轴对称流体模型,模拟脉冲电压下油中球板电极的放电过程,分析不同电压幅值与间隙距离对油中流注放电发展过程的影响。通过对油中流注放电这一过程进行仿真,比对不同条件下的流注发展情况和特性,并依据得到的流注放电过程的仿真结果,分析流注放电这一过程中影响其发展特性的一些影响因素进行对比分析。由于变压器油所处的工作环境极其复杂,因此在变压器的实际运行过程中,变压器油的绝缘性能受多种外部因素的影响。为了了解不同因素对变压器油绝缘特性的影响,设计试验,研究了不同温度以及间隙距离条件下,变压器油的击穿电压变化情况,并基于流注放电的理论和仿真对试验结果进行探讨。
[Abstract]:In the daily operation of transformers, the most important internal insulating medium is transformer oil, which shows that transformer oil plays an important role in ensuring the stable operation of power system. Therefore, its insulation performance directly affects whether the power grid can run stably. The theory of discharge in transformer oil is studied by studying the moving law of charged particles in electric field and its popularization and application. Whether it is an experimental study or a theoretical study of the principle of discharge in oil, and the analysis of different conditions or the law of liquid discharge under the electrode system, Therefore, it is very important to ensure the stable and safe operation of all kinds of electric power equipment. At present, in the process of studying the phenomenon of discharge in transformer oil, a great deal of research and experiments have been done and fruitful results have been obtained. In this paper, a series of theoretical and experimental results of transformer oil discharge are compared and a physical model of transformer oil flow-discharge development process is established based on the basic law of physical process. It includes electrode structure and simulation calculation area. In the development of transformer oil streamer discharge, there are two main factors that affect the physical process of transformer oil development, one is the moving process of charged particles in the electric field, the other is the influence of space charge on the electric field. By comparing the practice and consulting a lot of references, the feasible continuity equation of charged particle and the space Poisson equation of the effect of reactive charged particle on electric field are determined. At the same time, after consulting many related literatures, the transport and reaction coefficients of transformer oil flow-discharge simulation are found out, which are calculated by empirical formulas obtained from transformer oil flow discharge test. Then, considering the different conditions of physical model, charged particle continuity equation and space Poisson equation, the corresponding boundary conditions and parameter selection are determined. Considering that the convection term is much larger than the diffusion term in the solution of the continuity equation of charged particles, the artificial diffusion term is appropriately introduced to suppress the numerical oscillations in the solution process. Through the study of the generation and disappearance mechanism of space charge in transformer oil, the expression of space charge in the equation of continuity of charged particles is determined, and the ionization mechanism of field ionization is defined as the main ionization mechanism affecting the development of streamer discharge. The flow discharge in transformer oil was simulated with COMSOL Multiphysics software, and the corresponding two-dimensional axisymmetric fluid model was established to simulate the discharge process of spherical electrode in oil under pulse voltage. The effects of different voltage amplitude and gap distance on the development of flow discharge in oil are analyzed. By simulating the flow-discharge process in oil, the development and characteristics of the streamer under different conditions are compared, and the simulation results of the flow-discharge process are obtained. The influence factors on the development characteristics of streamer discharge are analyzed. Because the working environment of transformer oil is extremely complex, the insulation performance of transformer oil is affected by many external factors during the actual operation of transformer. In order to understand the influence of different factors on the insulation characteristics of transformer oil, the breakdown voltage of transformer oil was studied under different temperature and gap distance. The experimental results are discussed based on the theory and simulation of streamer discharge.
【学位授予单位】：东北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM41

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