An Investigation On Lightning Surge Protection Of Low-Voltage AC Power Lines

Lightning surges do harm to indoor electronic devices through low-voltage ac power lines. By analyzing how lightning affects indoor electronic devices and how to protect them effectively by surge protective devices (SPD), not only academic researches can be made but also can much economic profit be acquired.A theoretical and experimental study on the coordination of surge suppressors on indoor power lines is made. Different protective devices have different non-linear voltage-current characteristics and different response time. According to the detailed requirements of protective system, comparing the different characteristics of various surge protective devices can develop a reliable protective system. Simulations are done to study the coordination of SPDs under different chopping wave and long tail wave. To study the influences of the relative clamping voltages of the SPDs, the separation distance between the devices and the main waveforms of the surges can obtain an effective coordination. Results show which coordination is better and which is worse for a given surge.The relations with load features and the distance between SPDs and load are researched. Simulation analyse shows that impulse voltage on the side of load has consanguineous relations with load features and distance between SPDs and load by principle analysis of equivalent circuit and computer simulation. The dissertation analyses the protection effect of SPDs to pure resistive load, pure capactive load, inductive load, resistive and capactive paralleling load, and gets the effective protection distance.Protective circuits including MOV and filters are taken into account. High frequency components of surge can be suppressed and overvoltage can be reduced by the filter. On the principle analysis and simulation caculation, in the single-stage protective circuit of MOV coordinating with filter, the output voltage of protective device does not oscillate and overvoltage does not appear. The protective capability of cascaded protective circuit comprised of two-step cascade MOV and a filter is analyzed.