A reader wrote, "I have a contract to provide theatrical sound, stage-lighting and video services at a university. Recently, the university allowed multiple cell phone companies to install equipment on the roof of the theatre. The cell phone tower equipment installed by one company includes a conduit from the roof to the stage area catwalks on the inside of the building. The conduit is bonded via a decent gauge wire to the exposed steel of the building. The cell phone company also installed a heavy wire from inside the same conduit to the exposed steel of the building. My concern is, what happens in the event of a lightning strike or other electrical issue from their equipment? The building's steel is exposed throughout the catwalk area above the stage, and the steel most likely is also connected to our double-purchase rigging system steel. Are we at risk for a shock in this situation? Does it matter if the heavy wire is for lightning suppression versus just a heavy ground wire for their installation?" …The short answer to his question is that it should be safe to stand on the catwalk during a thunderstorm because the cell phone tower is bonded to the building. The reason for bonding them is to do our best to make sure all of the metal in the building structure, the cell tower, and the electrical system remain at the same voltage potential regardless of what might happen. Otherwise, a lightning strike or ground fault could create a difference in potential that could be very dangerous.
From "Focus on Fundamentals" by Richard Cadena, PLSN, August 2010
