Research On The Lightning Induced Overvoltage Of Low-voltage Lines And Coordination Of Surge Protective Device

With the development of society and technology, all kinds of electronic equipments have been widely used, and the electronic components of the equipments have a higher integration degree, but the tolerance level of electronic components is very low so that it is easily disturbed by lightning. Once the overvoltage of lightning and electromagnetic fields of lightning exceed the tolerance level of these components, it will cause the entire electronic equipment false operation, and even damage. Surge protective device(SPD) is one of the important means of modern lightning protection. Some of the existing domestic and international standards on installation configuration issues of SPD have inconsistencies, the coordination between surge protective device and loads, the effect of circuit parameters on SPD, the protection distance have not explicit instruction in these standards. For the safe and reliable operation of these electronic equipments, it is necessary to research the protection and coordination of SPD.Firstly, compared with the direct lightning, the frequency of overvoltage in lines caused by induced lightning is very higher. The overvoltage of induced lightning invades the indoor by the low-voltage lines(lines of signal and source), and disturbs the weak electricity equipments. So, the overvoltage of induced lightning in lines is studied, the cause of natural lightning is analyzed, and the two common function models of lightning current are introduced. Compared with the six kinds of lightning return-stroke channel model, choosing the Heidler function as the lightning current function model and the MTLL model as the return-stroke model to calculate and analyze the lightning electromagnetic field. Combined with the calculated results of lightning electromagnetic, calculating the induced lightning overvoltage of terminal lines by the Agrawal model.Secondly, the equivalent model of the induced lightning overvoltage in ATP-EMTP is established, and the simulation model of SPD is built. The distribution of SPD and the parameters of SPD are introduced.Finally, the characteristic of loads has great effect on the coordination of SPD. This thesis mainly deeply analyses the coordination of SPD and electronic equipment in theory and makes simulation, based on code for design structures against lightning. In the process of study on coordination of SPD and electronic equipment loads, mainly analyzes the protection distance of SPD, the two-level coordination of SPD, the affect of different circuit parameters on SPD. At last, prove the correctness of the theoretical analysis by software simulation.