This project was to design and install lightning protection equipment to protect Anemometers (wind speed measuring instrument) located at each of the 4 corners on the roof of a tall building at the UofA main campus. The anemometers are installed at the top of 17 ft masts, and are susceptible in a lightning storm.

We used IEC 62305-2 Lightning Protection Standard to conduct a risk analysis to determine the level of risk for the building in question and evaluated the Rolling Sphere Method (RSM) and the Protection Angle Method (PAM) and we decided to design to the PAM, as it was more conservative. The minimum lightning rod elevation required by the 45-degree cone angle of the PAM method provided a protection sphere with the 2.25 times the radius when the same elevation difference was used in the rolling sphere method. The rolling sphere assumes a 150 ft radius lightning sphere.

The final design included an air terminal, aluminum Lightning Braid Conductor and clamps. The Lightning Conductor is bonded to the steel pipe, and the mast is terminated to the existing ground grid.

Lexus Engineering did the design, and was also involved in the parts procurement and installation.

References: IEC 62305 – Lightning Protection Standard, NFPA 780 – Standard for the Installation of Lightning Protection Systems, Rolling Sphere Method (RSM), Protection Angle Method (PAM)