雷击输电线路杆塔地中散流特性的仿真与研究

发布时间：2018-08-27 12:17

【摘要】：当雷电直击输电线路杆塔时,由于雷电流幅度巨大,使其在大地流散中电流密度很大并且伴随着不同程度的土壤击穿过程。而很多输电杆塔接地系统虽然能满足接地电阻的总体要求,却在设计时对地下散流缺乏专门的、系统的研究,入地电流在地表、地中无规则窜动,严重影响周边生物的安全。例如:近年来,珠三角地区甚至已出现危害生物安全的事故,比如输电线路杆塔附近鱼塘在雷雨过后,鱼塘中的不同鱼类大量死亡的现象时有出现,佛山供电局管辖范围内已出现多起,由此造成地方供电局与当地农民之间的较多纠纷。为解决该问题,亟需通过现场勘察和仿真研究,建立相关设计和改造指导意见,提出对应的防护措施。本文采用COMSOL Multiphysics有限元软件进行仿真建模,为了建立符合现场实际情况的地中瞬态雷电流散流泄放过程的仿真模型,首先对雷电流波形以及能量分布进行分析;在对雷电流地中散流过程进行理论分析的基础上,逐步建立描述该物理过程的数学模型;根据得到的物理限制设置模型边界条件,结合输电线路杆塔接地系统、地下环境、周边雷电流分布的现场勘察与分析,利用各频率下KR-1G型接地装置的接地阻抗值与国际公认的接地专业软件CDEGS的仿真计算结果进行比对,其结果基本一致,可以认为本文仿真模型可以近似反映各频域下电流在接地装置上的流散状态,验证了该仿真模型的正确性。根据仿真结果表明:随着土壤电阻率的增大,将使得水中电流密度和鱼体电流密度持续上升,但上升趋势渐缓;接地装置的结构将影响地中电流密度的大小,地中高电流密度区域基本为接地良导体的形状;随杆塔接地装置与鱼塘距离的增大,鱼塘中电流密度越来越小,存在一定的安全距离,但是在土壤电阻率较高的地方安全距离将相应增大;而在相同雷击杆塔事故中,随着鱼塘深度的变化,生活在鱼塘底部的鱼类相比生活在鱼塘表面的鱼类受地中散流影响较小;鱼塘尺寸的变化对地中以及鱼塘中各部分的鱼体电流密度影响较小,可以忽略其影响。综合研究结论提出设计和改造方案:针对事故现场土壤条件较好时,通过对杆塔接地装置进行绝缘屏蔽改造,并加设反向延伸水平接地极;或是通过扁铜芯制绝缘引线外引地网,将接地装置引至距离鱼塘一定距离处散流,将可以避免事故的发生。针对杆塔和鱼塘已存在一定距离的情况下,通过在接地装置和鱼塘之间加设绝缘挡板,阻断雷电流向鱼塘侧流散的路径,更加经济适用,实际工程改造简易可行。
[Abstract]:When lightning strikes directly on the transmission line tower, because of the huge lightning current amplitude, the lightning current density in the earth dispersion is very high and accompanied by different degrees of soil breakdown process. However, many transmission tower grounding systems can meet the overall requirements of grounding resistance, but there is no special systematic research on underground diffusing current in the design, and the earth current does not move regularly on the surface and in the ground, which seriously affects the safety of the surrounding organisms. For example, in recent years, in the Pearl River Delta region, there have even been incidents endangering biosafety, such as fish ponds near the transmission line tower, where a large number of different fish in fish ponds die after a thunderstorm. There have been many cases within the jurisdiction of Foshan Power supply Bureau, resulting in more disputes between local power supply bureau and local farmers. In order to solve this problem, it is urgent to establish relevant design and reconstruction guidance and put forward corresponding protective measures through field investigation and simulation research. In this paper, the COMSOL Multiphysics finite element software is used to simulate the model. In order to establish the simulation model of the transient lightning current discharge process in the field, the waveform of lightning current and the distribution of energy are analyzed at first. Based on the theoretical analysis of the scattering process in the lightning current ground, the mathematical model describing the physical process is established step by step, and the model boundary condition is set up according to the physical limitation, and the underground environment is combined with the transmission line tower grounding system. The field investigation and analysis of the lightning current distribution around the ground, using the grounding impedance of the KR-1G grounding device at various frequencies, are compared with the results of the simulation calculation of the internationally recognized grounding professional software CDEGS, and the results are basically consistent. It can be considered that the simulation model in this paper can approximately reflect the current dispersion state in each frequency domain on the grounding device, and verify the correctness of the simulation model. The simulation results show that with the increase of soil resistivity, the water current density and the fish body current density will continue to increase, but the rising trend will gradually slow, and the structure of the grounding device will affect the magnitude of the ground current density. The area of high current density in the ground is basically the shape of a good grounding conductor, and with the increase of the distance between the grounding device of the pole tower and the fish pond, the current density in the fish pond becomes smaller and smaller, and there is a certain safe distance. In the same lightning tower accident, with the change of the depth of the fish pond, the fish living at the bottom of the fish pond is less affected by the ground mass than the fish living on the surface of the fish pond. The change of fish pond size has little effect on the current density of the fish body in the ground and in each part of the fish pond, which can be ignored. In view of the good soil condition of the accident site, the insulation shielding and retrofitting of the grounding device of the pole and tower are carried out, and the horizontal earth pole with reverse extension is added. Or through the flat copper core insulation lead wire outside the ground net, the earthing device will lead to a certain distance from the fish pond to disperse current, can avoid the accident. In view of the existing distance between the pole tower and the fish pond, it is more economical and feasible to install insulation baffle between the grounding device and the fish pond to block the path of lightning flowing to the side of the fish pond, and the practical engineering reconstruction is simple and feasible.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM863

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