Lightning: understand the dangers of lightning and know how to protect yourself

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Lightning strikes directly into the electrical grid or its vicinity, especially in open and high places, causing an increase in voltage. This overvoltage propagates in the grid until there is a point with passage to the ground.

For the protection of buildings, it is necessary the use of lightning rods in compliance with ABNT NBR 5419 standard. One of them is the rod type lightning rod (also known as Franklin lightning rod), installed at the top of buildings. This equipment offers protection for the building (or part of it) enclosed under the protective cone, whose apex is at the top of the capture rod.

The Franklin method does not apply to all types of buildings, so other methods (electro geometric, mesh or Faraday cage) should be used, in compliance with ABNT NBR 5419. For buildings above 60 meters, only the Faraday cage method is applicable. In any of the methods used, it is necessary to have adequate grounding. Radioactive surge arresters do not provide adequate protection and their use is forbidden in Brazil.

For antennas installed on buildings, the antenna support or anchorage point must be properly grounded. When the antenna is not located at the top of the building, special precautions such as additional grounding and shielding installation are required.

Efficient operation of the lightning rod and adequate overvoltage protection are associated with an effective grounding system. The type of grounding and the number of grounding electrodes (ground rods) to be used to ensure the effectiveness of the grounding depend on the soil characteristics.

Protection of low voltage grids.

There are several devices for protection of low voltage grids. The most common are low voltage lightning rods (varistors), surge suppressors, which can be found in specialized stores. 

For the correct operation of this equipment, it is necessary that it is properly specified, that the electric grid is well grounded, and that the neutral conductor is continuous, well sized and well spliced. Good grounding (rods, ground mesh, descending conductors) is the responsibility of the property owner.

It is essential that the installation has the protective conductor. This conductor is connected to the third pins of all the outlets and in turn it is connected to the grounding system and the MEB – Main Equipotential Bus.

It should be noted that the neutral conductor and the protective conductor have different functions in the installation.

For sensitive equipment such as television, there are other types of protection that are installed in the outlets. These devices are known as surge protectors. Computers, answering machines or even televisions require special protection.

For the efficient operation of any protective device of this equipment, it is necessary that the grounding system of the installation is also efficient. In the event of a poor grounding, the devices may not work perfectly, thus compromising the safety of the system and its users.