Had a similiar problem when I was chief engineer at an AM-FM radio station. The antenna tower was within 250 ft of the building. The prior engineer connected a copper strap from the automation equipment to one of the tower legs.
Whenever we had a lightning strike on the tower you can see the lightning dance across the equipment. Due to the lightning many time I had to replace parts in the automation controller. I finally found the copper strap and removed it from the tower. No longer did I get any calls due to lightning causing automation equipment failure. I then got the owner to get an engineering crew to measure the tower to ground and found that the original grounding was falling and needed to be fixed. After that no longer had issues either with the FM transmitter or TV transmitter at that site. Also added lightning protestion on the AC coming into the building. David Aug 1, 2010 03:43:37 PM, Repeater-Builder@yahoogroups.com wrote: Whenever I read a report like this, I have mixed emotions. I am surprised that the injury occurred, which is impossible if the facility was properly designed and islanded in accordance with numerous standards, including NFPA 70, NFPA 780, and the Motorola R56 Manual. I am also angry that an official issued the statement that "...the communications system, including its 400-foot radio tower, are grounded in accordance with industry safety standards." That official, and the idiots who designed the communications center, should be fired and/or brought up on criminal charges. The key to a safe installation at a location with an on-site tower is to ensure that all utilities pass through a "window" where a common ground reference exists. Ideally, the tower should be right next to the facility, so that the same ground reference is used for both. The power transformer that feeds the control room should be in that room, not hundreds of feet away, and the secondary neutral of that transformer should be bonded to the same ground that is used by the telephones, radio system, cable TV, satellite system, and raised-floor supports. If executed properly, the design of the control room creates a Faraday Cage within which all occupants are safe from injury due to GPR (Ground Potential Rise) from a nearby lightning strike. Likewise, all the electronics within the control room are protected against surge damage. It is obvious from the news report that the dispatcher was injured because her headset was at a different potential from her body. The GPR resulting from lightning striking the tower led to thousands of volts difference between the radio control system (the headset) and the floor and counter in the control room- and the chair she was sitting in. It is also obvious that this difference in potential could not exist if the tower and the adjacent control room were grounded in accordance with industry safety standards. Some common sense and credible engineering skills are essential elements in a proper control room design. Many moons ago (late 60's), I was Chief Engineer at radio station WLRW, a 50 kW FM station at Champaign-Urbana, Illinois. During my watch, the station control room was relocated to a building next door. It was my job to supervise the cabling installation within the building and to the transmitter at the base of the tower, which was just over 100 feet away. All of the remote circuits and network feeds came through a grounding window that was common with the power and the tower grounding system. I remember arguing with the Illinois Power foreman about how we needed a separate transformer to power the station, and it had to be installed right at the side of the control room and not in a vault several hundred feet away. The value of designing the entire installation to comply with established industry standards and sound engineering practices was proven many times, when the tower was struck by lightning during a storm, and no damage or injury occurred. Although the station was on automation most of the day, we had live talent from late afternoon to early morning, and at least one lightning strike occurred while on-air talent was at the board and wearing headphones. The lights blinked, but the board operator felt nothing and the show went on. 73, Eric Lemmon WB6FLY -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of tracomm Sent: Thursday, July 29, 2010 9:48 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] OT- Dispatcher injured by lightning strike A dispatcher was treated for electrical shock on May 2 after lightning sent a power surge through the dispatcher's headset. http://richmondregister.com/localnews/x1255109983/Lightning-surge-injures-91 1-dispatcher <http://richmondregister.com/localnews/x1255109983/Lightning-surge-injures-9 11-dispatcher>
