Assessment of lightning current distribution in subsequent lightning protection zones and selection of surge protectors

The subsequent evaluation model is used to assess the lightning current distribution at the boundary of protection zones after LPZ1. Since the user-side insulation impedance is much greater than the impedance of the surge protective device discharge branch and the external lead-in line, the lightning current entering the subsequent lightning protection zone will be reduced, and no special numerical estimation is required. Generally, the current-carrying capacity of the surge protector used in the subsequent lightning protection zone is required to be below 20kA (8/20μs), and the high-current-carrying capacity surge protection device is not required. The selection of surge protectors for subsequent lightning protection zones should consider the energy distribution and voltage coordination between each stage. When many factors are difficult to determine, using series-parallel surge protectors is a good choice. Series-parallel is a concept proposed based on the characteristics of many applications and protection range distinctions in modern lightning protection (relative to traditional surge protectors). Its essence is an effective combination of multi-stage dischargers and filter technology through energy coordination and voltage distribution. Series-parallel lightning protection has the following characteristics: wide application. It can not only be applied conventionally but is also suitable for locations where the protection zone is difficult to distinguish. The decoupling device's voltage division and delay effect under transient overvoltage helps to achieve energy coordination. Slowing down the rise rate of transient disturbances to achieve low residual voltage, long lifespan, and extremely fast response time.