PowerEarth was commissioned to assess the existing lightning protection system (LPS) on a communication tower for compliance. This was achieved with AS/NZS 1768. PowerEarth carried out a risk assessment and a computer analysis of the existing LPS system using SESShield (a 3D software). This revealed that the existing LPS did not provide adequate protection to the antennas mounted on the structure from direct lightning strikes.
These Simulation results are demonstrated in the figure below, as shown in the red zone.
Protection level II (97% interception efficiency) was sufficient enough for the tower against direct lightening strikes. However, the client’s requirement was to provide AS/NZS 1768 protection level I (99% interception efficiency). This was to further reduce the risk against direct lightening strikes to the antennas.
For the protection against direct lightening strikes to the antennas, our recommendations were:
Installing additional air terminals to provide necessary shielding.
Mounting horizontal steel bars with a minimum diameter of 10mm on the tower directly above each. Each steel bar needed to at least extend 0.5 beyond the extremity of the antennas as shown in the figure below.
We successfully fulfilled the clients requirements and the lightning protection system design was delivered.
– Electrical Engineer