{"id":9,"date":"2009-07-02T10:45:42","date_gmt":"2009-07-02T14:45:42","guid":{"rendered":"http:\/\/www.engineeringradio.us\/blog\/?p=3928"},"modified":"2023-07-09T07:56:15","modified_gmt":"2023-07-09T11:56:15","slug":"summer-thunderstorms-and-grounding","status":"publish","type":"post","link":"https:\/\/www.engineeringradio.us\/blog\/2009\/07\/summer-thunderstorms-and-grounding\/","title":{"rendered":"Summer thunderstorms and grounding"},"content":{"rendered":"\n

Most (if not all) radio engineers cringe when they hear a clap of thunder.\u00a0 Then the waiting begins.\u00a0 What are we waiting for?\u00a0 The cellphone to start ringing, of course.\u00a0 Over the twenty or so years I have been doing this, I have learned a few things.\u00a0 One of them is you cannot overground something.<\/p>\n\n\n\n

That being said, you can, of course, ground something improperly.<\/p>\n\n\n\n

The worst areas we have for lightning damage are the Gainesville\/Pensacola markets.\u00a0 Those places are in the lightning capital of the US.\u00a0 Time was our class C FM station was getting knocked off a couple of times a month.<\/p>\n\n\n\n

\"US
US Thunderstorm Days map<\/figcaption><\/figure>\n\n\n\n

There is hope.  When we upgraded the stations and installed new transmitters in 2004 I insisted that the tower and building be properly grounded.  I even got into an argument with the CFO about the “mission creep” as he put it.  Never mind that I put $20K in the initial work specification for grounding.<\/p>\n\n\n\n

There are a couple of strategies to use when dealing with lightning at transmitter sites:<\/p>\n\n\n\n

    \n
  1. Grounding:\u00a0 First, foremost, and always.\u00a0 Grounding should consist of multiple ground rods driven as deeply into the earth as possible.\u00a0 At the Trenton Florida transmitter site, we used 20-foot-long ground rods driven in 20 feet apart all the way around the building and in five 60-foot spokes around the tower.\u00a0 All of these ground rods and tower bases were bonded with #2 solid copper wire CAD (exothermically) welded to the ground rods.\u00a0 All turns were kept to a large diameter radius to keep inductance down.\u00a0\u00a0 When lightning strikes the tower, this creates a large electron sink to dissipate the strike energy into.<\/li>\n\n\n\n
  2. Bonding:  All equipment cabinets, racks, and everything metal is bonded together and to the same ground point presented by the grounding system.  When lightning strikes, often the ground cannot dissipate the energy fast enough.  When this happens, the entire ground area around the tower gets charged up.  Current will only flow down a less resistive path.  If everything is bonded together, the potential between any piece of equipment or component is the same, even if that potential is +10,000 volts.  No flow of current means no damage.<\/li>\n\n\n\n
  3. The transmitter building is located away from the tower.\u00a0 At almost every FM and TV transmitter site I have visited, the building is right smack at the tower base.\u00a0 By moving the building away about 100 feet or so, the EMP from the tower strike has dissipated (log function) significantly before it passes through the transmitter building.\u00a0 It is a little more expensive to install due to the added transmission line lengths and losses, however, it works.<\/li>\n<\/ol>\n\n\n\n

    I have been at the Trenton Florida transmitter site when lightning struck the tower.\u00a0 The result, not even a transmitter overload.\u00a0 Nothing was noticed on the air, no damage was sustained by any equipment.\u00a0 For the last five years, there has been no off-air time due to lightning damage at this site.<\/p>\n\n\n\n

    \"Studio
    Studio building with lightning rod, Gainesville, Florida<\/figcaption><\/figure>\n\n\n\n

    The studio site has a similar story.\u00a0 We built a new studio building in 2005, there is a 100-foot monopole that holds the STL antennas.\u00a0 You know that it gets hit during a storm.\u00a0 I remember the manager and IT guy from Pensacola commenting about how nice the new SAS Rubicon consoles were.\u00a0 Both of them also said that they wouldn’t last through the first summer because of lightning damage.\u00a0 Four years later, not a single incident of damage to the consoles, computers, or anything else in the building because we grounded everything as I described above.<\/p>\n\n\n\n

    Proper planning and installation pays off.<\/p>\n","protected":false},"excerpt":{"rendered":"

    lightning damage can be mitigated by proper planning and installation<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[7,5,6,8],"class_list":["post-9","post","type-post","status-publish","format-standard","hentry","category-tech-stuff","tag-installations","tag-lightning","tag-tech-tips","tag-transmitter-site"],"_links":{"self":[{"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/posts\/9","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/comments?post=9"}],"version-history":[{"count":6,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/posts\/9\/revisions"}],"predecessor-version":[{"id":12066,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/posts\/9\/revisions\/12066"}],"wp:attachment":[{"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/media?parent=9"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/categories?post=9"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.engineeringradio.us\/blog\/wp-json\/wp\/v2\/tags?post=9"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}