Research On Lightning Protection Of Secondary Devices

In recent years, over-voltage damages of secondary device caused attentions of more and more people. The surge protective devices(SPDs)(such as gas discharge tube,varistor,transient voltage suppression diode)is the simple measures to suppress the surge. However, these methods can't suppress the high frequency component in the surge. Because the influence of distributed induction and distributed capacitance during using the SPDs, it become limited to suppress the high frequency component. In order to control the high frequency component in the surge, the low-pass filter was used widely. Therefore the SPDs and the filter are combined to form a new surge suppressor which call combined surge protective device. It has the merit of the two devices, and remedy the demerits of both.it has good surge protection characteristic.Firstly, this paper introduces the three forms of lightning and the fundamental methods of lightning protection. Then describe the lightning mechanic and its character. Through the spectrum analysis of the typical over-voltage or over-current waveforms, it is show the distributing instance of lightning energy waveforms and showed that the main energy of the waveforms is in low frequency.By the wave propagation theory, analyse the parallel varistor and filter circuit. It determined the type of the filter circuit and the relationships of the filter circuit's parameters and output voltage. Based on the characteristics of varistor, the influence of the different impedance values between the protective devices is discussed.Finally, through analysis the result of simulation and experiment, it is show that the combined surge protective device has good protection features.and generalize the filter circuit's parameters. Study the influence of the relative clamping voltage of SPDs and the separate distance between the devices under the chopping wave.