Effectiveness of Lightning Protection Devices

The primary factors that affect the performance of lightning protection devices consists of shape and geometry of the devices, distance from the device to the ground and polarity of the lightning stroke. The theory about the effect of the dissipation charges is one of many concepts that have been used to study lightning protection. The use of devices that affect the dissipation of charges has been widely discussed for many years. In previous years, some studies were focused only on the magnitude of the emission current from these devices, but the lightning performance of the devices can also be evaluated by measuring the critical flashover voltage (CFO) between the devices and the metal screen simulating cloud. Under controlled condition, laboratory measurements were conducted for different devices in order to compare these devices. In the present study, the tested devices include Franklin rod, TerraStat models TS 100, TS 400 and spline ball ionizer. These four devices are different in configuration. The study focused on the CFO voltage of the air gap between the devices and a metal screen. The CFO voltage was evaluated using standard 250/2500 mus switching impulses and also 1.2/50 mus lightning impulses with negative and positive polarity. Measurements were taken at 2 m and 3 m air gap spacing between the metal screen and the devices. The metal screen was energized with a 3 MV impulse voltages generator. The voltage magnitude and waveshape were recorded by means of a digital oscilloscope via the output of the capacitive voltage divider. The test results provide a better understanding of the lightning protection devices´ electrical performance.