One of the buildings at your facility has a lightning protection system. Yet, the building shell sustained lightning damage during a recent storm. Worse, there was damage to several distribution panels and associated equipment. The plant manager wants you to determine what are wrong with the lightning protection system and that big surge protection panel at the service entrance.
How can you best answer your plant manager's concerns, and what steps should you take to properly investigate these issues?
There may be nothing wrong with your lightning protection system. These systems don't reach out and grab incoming lightning. Instead, they provide a preferred path and conduct the lightning to ground. While a properly designed and maintained system greatly reduces the odds of a direct strike, there are no guarantees.
But is your system properly designed? Review it against NFPA 780 and LPI-175 to determine if it is.
Over time, these systems deteriorate. Conduct ground testing to determine the condition of your grounding system. Ground testing is widely misunderstood and often done incorrectly; consider hiring a ground testing firm. Then visually inspect the entire system, from the air terminals to the point where each down conductor connects to the grounding system.
It's good to have surge protection at the service. But a single unit cannot possibly protect against the entire range of transient energy. You need a staged system that coordinates protection levels with power distribution levels.
Make sure you don't have any ground (earth) connections on the load side; your lightning protection system sends lightning to ground.
