【摘要】：當(dāng)雷電直擊輸電線路桿塔時,由于雷電流幅度巨大,使其在大地流散中電流密度很大并且伴隨著不同程度的土壤擊穿過程。而很多輸電桿塔接地系統(tǒng)雖然能滿足接地電阻的總體要求,卻在設(shè)計時對地下散流缺乏專門的、系統(tǒng)的研究,入地電流在地表、地中無規(guī)則竄動,嚴重影響周邊生物的安全。例如:近年來,珠三角地區(qū)甚至已出現(xiàn)危害生物安全的事故,比如輸電線路桿塔附近魚塘在雷雨過后,魚塘中的不同魚類大量死亡的現(xiàn)象時有出現(xiàn),佛山供電局管轄范圍內(nèi)已出現(xiàn)多起,由此造成地方供電局與當(dāng)?shù)剞r(nóng)民之間的較多糾紛。為解決該問題,亟需通過現(xiàn)場勘察和仿真研究,建立相關(guān)設(shè)計和改造指導(dǎo)意見,提出對應(yīng)的防護措施。本文采用COMSOL Multiphysics有限元軟件進行仿真建模,為了建立符合現(xiàn)場實際情況的地中瞬態(tài)雷電流散流泄放過程的仿真模型,首先對雷電流波形以及能量分布進行分析;在對雷電流地中散流過程進行理論分析的基礎(chǔ)上,逐步建立描述該物理過程的數(shù)學(xué)模型;根據(jù)得到的物理限制設(shè)置模型邊界條件,結(jié)合輸電線路桿塔接地系統(tǒng)、地下環(huán)境、周邊雷電流分布的現(xiàn)場勘察與分析,利用各頻率下KR-1G型接地裝置的接地阻抗值與國際公認的接地專業(yè)軟件CDEGS的仿真計算結(jié)果進行比對,其結(jié)果基本一致,可以認為本文仿真模型可以近似反映各頻域下電流在接地裝置上的流散狀態(tài),驗證了該仿真模型的正確性。根據(jù)仿真結(jié)果表明:隨著土壤電阻率的增大,將使得水中電流密度和魚體電流密度持續(xù)上升,但上升趨勢漸緩;接地裝置的結(jié)構(gòu)將影響地中電流密度的大小,地中高電流密度區(qū)域基本為接地良導(dǎo)體的形狀;隨桿塔接地裝置與魚塘距離的增大,魚塘中電流密度越來越小,存在一定的安全距離,但是在土壤電阻率較高的地方安全距離將相應(yīng)增大;而在相同雷擊桿塔事故中,隨著魚塘深度的變化,生活在魚塘底部的魚類相比生活在魚塘表面的魚類受地中散流影響較小;魚塘尺寸的變化對地中以及魚塘中各部分的魚體電流密度影響較小,可以忽略其影響。綜合研究結(jié)論提出設(shè)計和改造方案:針對事故現(xiàn)場土壤條件較好時,通過對桿塔接地裝置進行絕緣屏蔽改造,并加設(shè)反向延伸水平接地極;或是通過扁銅芯制絕緣引線外引地網(wǎng),將接地裝置引至距離魚塘一定距離處散流,將可以避免事故的發(fā)生。針對桿塔和魚塘已存在一定距離的情況下,通過在接地裝置和魚塘之間加設(shè)絕緣擋板,阻斷雷電流向魚塘側(cè)流散的路徑,更加經(jīng)濟適用,實際工程改造簡易可行。
[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.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM863

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