A Novel SPD Design for Lightning Protection of Intelligent Buildings

The surge protective device (SPD), as buildings over-voltage protective device, has been widely used in building's power distribution system. A novel SPD based on hollow cathode effects is designed. In both air and nitrogen gas, the relationship of discharging voltage and gas pressure are measured, and the critical pressure ranges are determined in the condition of U-p<4 kV (U-p is pulse voltage protection level). The results indicate that, in the condition of the gap distance D=3 mm and the small hole diameter phi=3 mm, the operating gas pressure ranges are from 50 to 5x 10(4) Pa. With the gap distance D increasing, the pulse voltage protection level U-p is decreasing slightly. While D=3 mm, phi=3 mm, and gas pressure (nitrogen) is 600 Pa, the DC voltage protection level and pulse protection level are 784 V and 2.4 kV, respectively. In the action of 10/350 mu s pulse current waveform, the quantity of transferred charge Q is 48.26 C, and the ratio energy W/R is up to 2 MJ/Omega. The results testify that the design of SPD in this paper can be used as buildings class B over-voltage protection.