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Outdoor explosion-proof control boxes – Grounding requirements for explosion-proof electrical control boxes. During the normal operation of outdoor explosion-proof control boxes, it is inevitable to encounter rainy and thunderous weather. On rainy days, these explosion-proof devices need power to function. In the electric power industry, overvoltages caused by lightning are types of impulse voltages with a short duration; under such impulse voltages, the breakdown of air gaps exhibits distinct characteristics, which is why it is necessary to install explosion-proof devices. Requirements for grounding of outdoor explosion-proof control boxes and explosion-proof electrical control boxes: For explosion-proof control boxes that operate outdoors, it is necessary to equip them with grounding devices to prevent damage from lightning strikes. To ensure the safety of such outdoor explosion-proof control boxes, the following measures should be taken: Before a lightning discharge occurs, thunderclouds can have extremely high static electric potentials relative to the ground surface, reaching levels in the range of 10 to 10^9 volts. However, the potential of an outdoor explosion-proof control box that has been struck is something different from the potential of a thundercloud before discharge. In fact, high-voltage fuse devices can handle the high voltages that occur during lightning strikes and can also protect against the massive surge currents generated by such discharges. Outdoor explosion-proof control boxes can prevent explosions caused by overvoltages resulting from lightning or high-voltage currents. When lightning strikes near a power transmission line, the intense fluctuations in the electric and magnetic fields caused by the lightning current can result in very high voltages being induced across the line as well. Therefore, the massive impulse current generated by lightning is the source of its destructive power; it can cause a sudden rise in voltage, and it also has electrical and mechanical effects. In such cases, explosion-proof enclosures must possess lightning and explosion protection capabilities to prevent harm to human safety. After a thunderstorm occurs, the electric field strength at certain areas of the ground increases dramatically due to the effect of the thunderclouds. Once the average field strength reaches a sufficient level, spark discharge can occur in the air between the thundercloud and the ground, resulting in what is known as a lightning discharge. There are opposite charges in thunderclouds, so lightning discharges can also occur within them. But it is clearly the discharges from thunderclouds to the ground that cause harm; lightning generates extremely high voltages. Therefore, it is very important to install explosion-proof box equipment in many places, as this is a key measure to prevent accidents caused by lightning. A lightning strike is a discharge phenomenon in the atmosphere caused by the accumulation of large amounts of charge in thunderclouds. The vast majority of lightning discharges are of negative polarity (the thunderclouds carry a negative charge), but positive-polarity lightning discharges have also been observed. Lightning discharges can generate high voltages on explosion-proof box equipment; lightning currents impact the electrical circuits. The high voltages resulting from lightning discharges also have a shockwave pattern, which is why explosion-proof boxes need to be installed both in outdoor and indoor areas to prevent greater damage caused by lightning strikes. Outdoor explosion-proof control boxes and explosion-proof electrical control box equipment require power supply in order to function. In the electric power industry, overvoltages caused by lightning are types of shock voltages with a short duration. Under such shock voltages, the breakdown of air gaps exhibits distinct characteristics, hence the necessity of installing explosion-proof box equipment.