| Lightning is serious harm to electrical and electronic equipment and high voltage power transmission equipment in buildings through various means. Lightning overvoltage can not only cause the wrong operation of electrical and electronic systems, but also may cause permanent damage to the device. The installation of surge protection device with reliable performance (SPD) is to reduce one of the important methods of lightning damage. ZnO varistors are the core device of surge protection device, and it is widely used because of its good energy absorption ability and excellent nonlinear. Currently, in the conventional performance evaluation and testing of ZnO varistor products, we use 8/20 ?s single pulse which is simulated natural lightning to test the lightning protection products, and the test results to measure the quality of the SPD. However, more and more observations show that:multiple lightning is a common phenomenon in natural lightning,80% of the natural lightning is multiple lightning process. The single pulse which is used as the shock wave is not in conformity with the modern lightning observation data. The single pulse to simulate the natural lighting is obvious difference with the repeatedly lightning return stroke process. The natural lightning with multiple return stroke waveform process is completely different from that of the single pulse in time and energy. Therefore, SPD with the single pulse test quality is qualified, may not have or do not have the ability to withstand the impulse of lightning impulse. In this paper, we use the most advanced multi-pulse high voltage lightning test platform in order to simulate the natural lightning impulse waveform to the maximum extent. And the paper experimental study on multi-pulse impact of ZnO based on the pressure sensitive resistance. Firstly, make the analysis of the multi-pulse waveform from the integrated perspectives and have the calculation and comparative study of lightning-pulse energy and pulse energy. Then, with the changing environmental factors, explore the laws of ZnO varistors' static parameters (varistor voltage and leakage current) in the multi-pulse and single-pulse shock process. To make comparative analysis of the obtained results and explain ZnO varistors aging process combined with theoretical thermal behavior. Finally, with the use of control variables method which changes the source of the impact of multi-pulse interval and the number of pulses and other factors, and explore the degradation and destruction in the form of ZnO varistors. This paper sums up the four aspects as follows:(1) This paper summarizes the research process of the natural lighting in recent years, calculate and analyse the lightning multi-pulse energy and single-pulse energy. (2)By the experiments that varistor static parameters were compared under the single-pulse and multi-pulse shocks in the normal temperature and humidity the environment. And explore the aging deterioration of ZnO varistors under the impacts of two different sources by the use of varistor dielectric properties as well as its principle of internal changes in grain boundary structure. Above these, to learn more about the ZnO varistors' aging process under the multi-pulse shocks which is close to the real natural environment lighting completely; (3) By the damp heat box and multi-pulse platform, to explore the ZnO varistors aging deterioration characteristic in the real environment which is wet or contaminated by salt mist, and try to provide a reference for the R & D production work of creating the new ZnO varistors which can withstand the harsh conditions of multiple lightning in the future. (4) Using the control variable method, by changing the course of the multi-pulse shock pulse spacing and pulse amplitude of the impact and the load operation, to research the ZnO varistors' failure characteristics and failure mode. |
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