特高压电晕笼交流离子流场与电晕损失数值仿真研究

发布时间：2018-11-08 14:16

【摘要】：导线电晕放电产生的电晕损失是线路设计的重要考虑因素,通常利用特高压电晕笼进行不同分裂导线束的电晕损失研究。目前基于特高压电晕笼的电晕损失测量试验受到很多限制,测量质量和时间成本难以同时保证,且部分特征量无法通过试验测得,因此有必要从气体放电物理的角度研究导线电晕放电过程,建立电晕放电与电晕损失间的内在关联关系。本文从气体放电机理出发,建立了特高压电晕笼分裂导线交流离子流场数值计算模型,研究了导线附近电场强度的时空分布特性和电晕电流的时域、频域分布特性,而后利用功率因素法计算了不同交流电压下不同分裂导线的电晕损失,所得研究成果对实际输电线路电晕损失预测具有重要意义。主要工作如下:本文基于模拟电荷法建立了特高压电晕笼导线三维离子流场数值计算模型。模型考虑了导线的有限长特性、分裂导线表面场强不均匀性和笼体两侧均压环的影响,计算了三维空间内交流电压下导线起晕、空间电荷发射、迁移和复合等过程,并根据Shockley-Ramo法则提出了电晕电流的计算方法。而后对影响模型的各因素进行了分析研究,提出了最优化的模型参数。采用本文所建模型,以8×LGJ720导线为例,对其表面附近电场的时空分布特性和导线电晕放电所产生的电晕电流进行数值仿真研究。电场结果表明,导线表面场强沿线分布呈现出"中间和端部稍大"的规律,两侧均压环明显改善了端部效应;导线表面场强的时域分布因空间电荷的影响而轻微超前于电压波形;空间电荷分布对导线外0.5m范围内的场强有影响,与ANSYS仿真结果对比证明了模型的正确性。电晕电流的时域特性研究结果表明,交流周期不同时刻的电荷运动与电晕电流存在内在关系;采用FFT方法获取了电晕电流在低频条件下的幅频和相频曲线,结果表明奇数次谐波分量是电晕电流的主要组成。通过求取电晕电流工频分量的方法,分别计算了干燥和大雨条件下8×LGJ630导线在不同电压下的电晕损失,与武汉特高压交流电晕损失试验结果相符合,验证了模型的准确性。研究发现雨量20mm/h条件下8×LGJ630导线的起晕电压比干燥条件下小70kV,并且起晕后导线电晕损失随电压的增大,增幅更为明显。而后利用本文提出的模型对海拔高度、导线型号、分裂数、分裂间距四种影响因素进行研究,结果表明:海拔高度增加降低了导线起晕电压,使电晕程度更剧烈;起晕后导线电晕损失随导线型号和分裂数的增大而减小,随分裂间距的增大而增大;与武汉和西宁地区的试验结果对比,证明了模型的正确性。
[Abstract]:The corona loss caused by conductor corona discharge is an important factor in line design. The corona loss of different splitting conductor bundles is usually studied by using UHV corona cage. At present, the measurement of corona loss based on UHV corona cage is limited, the quality of measurement and the cost of time can not be guaranteed at the same time, and some characteristic quantities can not be measured by experiment. Therefore, it is necessary to study the corona discharge process of conductor from the point of view of gas discharge physics, and to establish the internal relation between corona discharge and corona loss. Based on the mechanism of gas discharge, a numerical model of AC ion flow field of split conductor with ultra-high voltage corona cage is established in this paper. The temporal and spatial distribution characteristics of electric field intensity and the distribution characteristics of corona current in time domain and frequency domain are studied. Then the corona loss of different split conductors under different AC voltages is calculated by power factor method. The results obtained are of great significance to the actual corona loss prediction of transmission lines. The main work is as follows: based on the simulated charge method, a numerical model of three-dimensional ion flow field for ultra-high voltage corona cage conductor is established in this paper. The model takes into account the finite length characteristics of the conductor, the non-uniformity of the surface field strength of the split conductor and the influence of the pressure sharing ring on both sides of the cage body. The processes of wire halation, space charge emission, migration and recombination are calculated under the alternating voltage in three dimensional space. The calculation method of corona current is put forward according to Shockley-Ramo rule. Then the factors influencing the model are analyzed and the optimal model parameters are put forward. Taking 8 脳 LGJ720 conductors as an example, the spatiotemporal distribution of electric field near its surface and the corona current produced by corona discharge of conductor are studied numerically by using the model established in this paper. The results of electric field show that the distribution of electric field intensity along the wire surface is "slightly larger at the middle and the end", and the end effect is obviously improved by the two-side uniform pressure ring. Due to the influence of space charge, the distribution of the field intensity on the surface of the conductor is slightly ahead of the voltage waveform, and the distribution of the space charge has an effect on the field intensity in the range of 0.5 m outside the conductor. The results of ANSYS simulation show that the model is correct. The time domain characteristics of corona current show that there is an inherent relationship between the charge motion and the corona current at different times of AC cycle. The amplitude-frequency and phase-frequency curves of corona current at low frequency are obtained by FFT method. The results show that the odd-order harmonic component is the main component of corona current. By calculating the power frequency component of corona current, the corona loss of 8 脳 LGJ630 conductor under different voltages under dry and heavy rain conditions is calculated, which is in agreement with the test results of Wuhan UHV AC corona loss, and verifies the accuracy of the model. It is found that the corona voltage of 8 脳 LGJ630 conductor under rainfall 20mm/h is 70 kV smaller than that under dry condition, and the corona loss increases more obviously with the increase of voltage. Then using the model proposed in this paper, four factors affecting the altitude, wire type, splitting number and split spacing are studied. The results show that the increase of altitude reduces the corona voltage and makes the corona degree more intense; The corona loss decreases with the increase of wire type and splitting number, and increases with the increase of splitting distance, and the model is proved to be correct by comparison with the experimental results in Wuhan and Xining.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM75

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