Ground Potential Rise and Surge Protective Device Damage Caused by Initial Long Continuous Current Process in Triggered Lightning

Abstract

In the field of grounding on electronic and electrical systems, damage effects of ground potential rise on electronic equipments are of great importance. Based on triggered lightning technology, an observation experiment is carried out on impacts of the ground potential rise in grounding grid upon surge protective device (SPD), especially on damage effects of initial long continuous current process of triggered lightning on SPD. It's found that upon injection of triggered lighting into grounding grid, SPD damage of rated flow rate is likely to occur under combined effects of initial long continuous current process and subsequent return stroke of triggered lightning. When the energy flowing through SPD is accumulated to a given extent, initial long continuous current process alone can also cause SPD damage. The impact on SPD is closely related to different waveforms of initial long continuous current process. When initial long continuous current process superposes ICCP with current of faster rise time and higher amplitude, energy flowing through SPD will increase rapidly, which is the most critical factor causing SPD damage in long continuous current process. The analysis of two cases indicates that, when the duration of initial long continuous current process and average current reaches about 100 ms and 200 A, the magnitude of discharge is 25 C, and energy flowing through SPD is up to about 1000 J, it is apt to cause 20 kA nominal discharge current and even higher SPD damage. Two processes (T0702 and T0726) of SPD are damaged by initial long continuous current of triggered lightning, when the peak value of current flowing through ground wire is 396.5 A and 392.7 A, respectively, the average current of main stage before damage is 23.6 A and 19.7 A, accounting for 10.8% and 6.7% of the average value of trigger lightning current, and the duration of current flowing through SPD above 50 A is 9.2 ms and 6.6 ms, respectively. When SPD is damaged, there is a sudden change in the residual voltage at both ends of SPD, which is obviously different from the disappearance of normal SPD residual voltage.

Keywords

• triggered lightning
• initial long continuous current
• ground potential rise
• surge protective device
• damage