| Line lightning strike failure is one of the biggest risks of safe,reliable and stable operation of oilfield lines.There are many characteristics of oilfield lines in voltage levels,large distribution range,high pollution level,and poor operating conditions of line equipment.In addition,Shengli Oilfield line faces with problems such as its old equipment,the high maintenance cost of the whole line,and its high grounding resistance in the saline-alkali area.These characteristics and problems lead to an increase in line lightning failure rate.Therefore,the research of high efficiency,maintenance-free lightning arrester and the reduction of line lightning protection cost are the research hotspots of oil field power grid at present.The thesis firstly investigates the data of the line parameters of the Shengli Oilfield power grid,the operation of the line,the lightning accident and the lightning protection measures adopted by the line.The main causes of the lightning damage in the Shengli Oilfield and the weak links existed are also analyzed.Secondly,based on the actual situation of Shengli Oilfield,the ATP/EMTP model of the typical oilfield is built.The lightning protection improvement measures of Shengli Oilfield are analyzed according to the simulation results,and the disadvantages of traditional protection gap and zinc oxide arrester are analyzed.Thirdly,in view of the problem that the traditional protection gap leads to high line trip rate,a new protection gap based on vacuum arc extinguishing principle is proposed.The relationship between the field strength of the vacuum interrupter and the contact opening distance is analyzed by ANSYS finite element software to determine the arc extinction.The minimum opening distance is determined.Push the equivalent equation of the conductive magnetic repulsion mechanism circuit,draw the pulse current and the contact motion curve.And the thesis builds the corresponding model in ATP/EMTP to verify its lightning protection effect on the typical oilfield line.Then,for the problem of high cost and leakage current of metal oxide arester(MOA),a time-varying arc-length arc model(VALM)is proposed to simulate the arcextinguishing process of multi-gap lightning protection structure.The VALM model is simulated by ATP/EMTP to analyze the dynamic arc extinguishing performance of multi-gap lightning protection structure after lightning strike,and to verify its lightning protection effect on typical oil field lines.Next,in order to verify the theory of VALM model,a multi-gap lightning protection structure prototype is designed.And it is tested for insulation coordination,impulse voltage and inrush current.The results show that the actual waveform is basically consistent with the simulation results of time-varying arc length arc model.Finally,the multigap structure is installed on the Chengsan line of Shengli Oilfield.After one year of trial operation,the Chengsan line lightning strike failure situation is significantly improved compared with previous years,and the line operation condition is good,indicating that the multi-gap lightning protection structure has better lightning protection effect.It can be applied to improve the lightning protection of Shengli Oilfield. |
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