Study On Lighting Over-voltage Of Underground Cables

Since time immemorial, lightning accidents occurs frequently. Various types of transmission equipment and electronic equipment have been invented with the development of science and technology. However, these objects are more or less affected by lighting.From the "field" or "road" angles, corresponding formulas have been obtained by the studies of different equipment striked by lighting.Cables are also vulnerable to the impact of lightning.The general approach is from the "road" angle,that is the cable circuit is equivalent to resistance, inductance, capacitance and conductance.we will obtain the corresponding equation by analysing the lightning electromagnetic field, a number of mathematical formulas, physics formulas, and engineering formulas .In addition, some formulas are given directly.we can determine whether the cable is struck by lightning or not.On the basis of these theoretical studies, for communication cable,we have established its underground location and analysed lightning induced overvoltage calculation.Then the programming flow chart is showed and we have programmed and made some simulation.Finally, we contrast,analyse the results of calculation and simulation ,and discuss various factors of lightning induced overvoltage.The lightning protection of communication cables are proposed.For optical cable,we have established its underground location and showed flow chart which can judge the optical cable can destroy by lighting or not.Finally,prevention measures of optical cable fault are put forward.In this paper, models of several grounding methods for power cables are established. Generating mechanism and calculation formula of overvoltage in security layer are analyzed, and programming flowchart of the formula is listed. The writer use FORTRAN programming for calculating the formula, which shows the correctness of the result. Also, prevention measures of power cable fault are put forward.The simulation lays a foundation for the development of lightning protection system, and the measures showed provide a reference for the steady operation of the cables.