How do you effectively design a lightning protection system for a building?

1 Assess the risk

The first step in designing a LPS is to assess the risk of lightning exposure for the building, based on its location, structure, function, and surroundings. You can use a risk assessment method, such as the one specified in the international standard IEC 62305-2, to calculate the probability of lightning damage and the acceptable level of protection. The risk assessment will help you determine the need and scope of the LPS, as well as the appropriate level of protection for each zone of the building.

2 Choose the components

The second step in designing a LPS is to choose the components that will form the system, based on the level of protection needed. Air terminals, down conductors, grounding electrodes, and surge protection devices (SPDs) are all essential components of a LPS. Air terminals are metal rods or wires installed on the roof or other exposed parts of the building, to direct lightning strikes. Down conductors are metal cables or straps connecting air terminals to the ground, carrying lightning current safely. Grounding electrodes are metal rods or plates buried in soil, providing a low-resistance connection between down conductors and earth. SPDs are devices installed on electrical and communication circuits of the building, protecting them from voltage surges due to lightning current or electromagnetic fields.

3 Design the layout

The third step in designing a LPS is to design the layout of the components, following the guidelines and recommendations of the relevant standards, such as IEC 62305-3 or NFPA 780. To ensure optimal protection, the air terminals should be distributed evenly and cover the entire roof area, as well as any protruding or vulnerable parts of the building, such as chimneys, antennas, or vents. Additionally, down conductors should be routed along the shortest and straightest path possible and spaced at regular intervals around the perimeter of the building. Furthermore, grounding electrodes must be located at least 3 meters away from the foundation of the building and interconnected by a ring conductor to form a grounding system that encircles the building. Finally, SPDs should be selected and installed according to the type and sensitivity of the circuits they protect, and coordinated with each other to avoid overvoltage or underprotection.

4 Verify the performance

The fourth step in designing a LPS is verifying the performance of the system, which can be done through simulation tools, testing methods, or inspection procedures. This verification should guarantee that the LPS meets the design criteria and specifications, such as the level of protection, the lightning current capacity, and the resistance and impedance of the components. Additionally, it should provide a continuous and uniform protection for the building without creating any gaps or weak points that could compromise its effectiveness. Lastly, it should not interfere with the normal operation of the building or cause any hazards or nuisances to the occupants or environment.

5 Maintain the system

The fifth step in designing a LPS is to maintain the system, which should involve regular inspections, repairs, and upgrades. This will ensure that the LPS is in good condition and works properly, without any damage or corrosion. It should also be adapted to any changes or modifications of the building, such as renovations or extensions. Additionally, the maintenance should make sure the LPS complies with current standards and regulations, and follows best practices and recommendations of the power engineering field.