初始长连续电流引起的地电位抬升和SPD损坏

在电子电气系统接地领域，地电位抬升对电子设备的破坏效应一直是人们关注的焦点。基于触发闪电技术，开展了地网地电位抬升冲击电涌保护器(surge protective device，SPD)的观测试验，重点分析了触发闪电初始长连续电流过程对SPD的冲击和损坏效应。结果发现，触发闪电注入地网后，闪电的初始长连续电流和继后回击的共同作用下很容易造成额定通流量的SPD损坏，当流经SPD的能量累积达到一定程度时仅初始长连续电流过程也会损坏SPD；冲击SPD的效应与初始长连续电流过程的不同的波形密切相关，当长连续电流过程叠加上升沿较快幅值较大的初始连续电流脉冲(ICCP，initial continuous current pulse)时，流经SPD的能量会迅速增加，是长连续电流过程中SPD损坏的最为关键因子。个例分析发现，当初始长连续电流过程持续时间和平均电流量级达到100 ms和200 A左右，泄放电量为25 C，流经SPD的能量达1000 J左右，易造成标称放电电流20 kA甚至更高的SPD损坏。

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

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.