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Principles and Category Analysis of Lightning Protection Devices
Power surge protectors are essential devices designed to safeguard electrical equipment from damage caused by voltage spikes, such as those resulting from lightning strikes. These protectors come in various forms, including single-phase and three-phase lightning protection boxes, single-phase and three-phase modules, and lightning protection sockets. They are commonly installed in critical infrastructure such as power distribution stations, rooms, cabinets, AC/DC panels, switchgear enclosures, and other equipment that is highly susceptible to lightning-induced surges.
The primary function of a power surge protector is to quickly divert the high-energy surge current caused by lightning or electrical transients into the ground within a very short time frame—typically on the nanosecond scale. This rapid response helps prevent damage to sensitive electronics and ensures the continuity of power supply.
Surge protection devices (SPDs) can be categorized based on their working principles: switch-type SPDs and voltage-limiting SPDs. Switch-type SPDs are typically used in zones 0 and 1 of lightning protection systems, where the risk of direct lightning strikes is higher. On the other hand, voltage-limiting SPDs are more suitable for subsequent zones, such as LPZ1 and beyond, where the energy levels are lower but still dangerous.
These devices are connected in parallel to the power line and grounded to the earth. Under normal conditions, the SPD remains in an open circuit state, allowing the flow of regular current without interference. However, when a surge exceeds the device's threshold, it rapidly switches to a conductive state, channeling the excess current safely to ground. Once the surge has passed, the SPD returns to its normal, non-conductive state.
Switch-type SPDs are typically constructed using components like discharge gaps, gas discharge tubes, thyristors, and triacs. Their operation involves a "on-off" mechanism, where they activate only when the surge current surpasses a certain level. These types of SPDs are known for their strong ability to handle large currents, capable of managing simulated lightning surges with a waveform of 10/350μs.
Voltage-limiting SPDs, on the other hand, are mainly composed of varistors and suppression diodes. Unlike switch-type SPDs, they do not fully disconnect but instead gradually increase their conductivity as the surge current increases. This allows them to limit the residual voltage on the power grid, making them ideal for applications requiring fast response times and low residual voltage. They are particularly effective at handling 8/20μs simulated lightning impulses.
By using these different types of surge protectors, industries can ensure reliable and safe power distribution, minimizing the risk of equipment failure due to electrical surges.