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Principles and Category Analysis of Lightning Protection Devices
Power surge protectors come in various forms, including single-phase lightning protection boxes, **three-phase lightning protection boxes**, single-phase modules, three-module systems, and lightning protection sockets. These devices are commonly used in critical infrastructure such as power distribution stations, electrical rooms, control cabinets, AC/DC power panels, switchgear enclosures, and other equipment that is both essential and susceptible to lightning damage.
The primary function of a power surge protector is to safely divert the high-current surge caused by lightning strikes or induced surges into the ground within a very short time frame—typically in the nanosecond range. This helps prevent damage to sensitive equipment connected to the power line.
Lightning protection devices are generally categorized into two types based on their working principles: switch-type surge protectors and voltage-limiting surge arresters. Switch-type SPDs are typically installed in Zone 0 to Zone 1 of lightning protection zones, where the risk of direct lightning strikes is higher. Voltage-limiting SPDs, on the other hand, are more suitable for use in LPZ1 and subsequent zones, where the energy levels are lower but still pose a threat.
A surge arrester is connected in parallel with the power line and grounded. Under normal conditions, the **lightning protector** remains in an open circuit state. However, when a surge exceeds its threshold, it quickly conducts the current to ground, effectively limiting the damage. Once the surge has passed, the device returns to its normal open state.
Switch-type surge protectors are typically made up of components like discharge gaps, gas discharge tubes, thyristors, and triacs. Their operation involves a "switch-on" and "switch-off" mechanism. When the lightning current exceeds the set threshold, they can handle large instantaneous currents, such as those simulated by a 10/350μs waveform. These devices are known for their strong current diversion capabilities.
Voltage-limiting surge arresters, on the other hand, are mainly composed of varistors and suppression diodes. Their key characteristic is that their ability to conduct current to ground increases as the surge intensity rises. They respond quickly to surges and significantly reduce the residual voltage on the power grid. These devices are effective in handling standard 8/20μs impulse currents, making them ideal for protecting electronic equipment from transient overvoltages.