[TowerTalk] Lighting

[Jerry Keller]

OK, one more try!  Your example describes the cloud as already over the tower. My "gradually and constantly bleeding off the charge" scenario takes place before that, before the storm arrives. In my scenario, the tower area rarely gets enough charge built up to be attractive. When the stormcloud arrives, the area around the tower is already "discharged", maybe even to a greater degree than other surrounding areas, so it looks less attractive to the charge in the cloud. That's what I call a sort of "prevention", but it's really just making the tower a less likely target.  

Your scenario has the ground charge moving to a point beneath the cloud "at will" and then discharging through the tower because it represents a shorter, easier path. If that were true, all towers would always be an easier path, and we'd have towers being struck every time a storm passes overhead... which we know, from observation, doesn't happen all that much.

So, how would you account for the well-grounded tower that doesn't get hit much if at all?  I say that nothing will absolutely prevent a strike if conditions are right.... BUT... by proper grounding methods we can both lessen the chances for a strike and protect our stuff if and when we do get one.  

Rich, KE3Q, describes a mini-version of the phenomenon remarkably well: "On a dry winter day when you're walking on the carpet at the office and then touch the metal drinking fountain you get a sudden static discharge, analogous to a lightning strike (though micro).  Touch something metal every few steps and the charge cannot build up to such a size.  You are discharging the buildup before it gets so big." 

Hope that helps turn on the "lightning bulb", Tom!! If not, well I tried. Keep the faith, my friend... 73, Jerry K3BZ


  ----- Original Message ----- 
  From: Tom Rauch 
  To: jerryc ; TowerTalk at contesting.com 
  Sent: Tuesday, July 06, 2004 9:52 PM
  Subject: Re: [TowerTalk] Lighting


  > Tom
  > I may be wrong but my take on this is that many of us were
  > told that structures not properly grounded would build up
  static
  > and be more likely to attract a strike.

  Well, let's think about that.

  Let's say the cloud is short a few electrons and the earth
  has extra.

  We magically insulate the tower so well it can't receive any
  electrons from the earth. Now the tower is neutral, floating
  midway between the cloud's potential and the earth's. Most
  of the potential difference is between the earth and cloud.

  Now we ground the tower, and since it is closer to the cloud
  charges move up into the tower. Hmmm. Now the tower has the
  highest field gradient to the cloud!

  If a charge leaks off as corona, it is attracted towards the
  cloud. Now the path is shorter!

  I'm really sure this stuff that the charge bleeds off is
  nonsense Jerry. Unless someone else can explain how
  grounding the tower moves the tower TOWARDS the potential of
  the cloud (reducing voltage gradient), or how corona leaving
  the tower is magically repelled from the cloud that pulled
  it up and out in the first place.

  All someone has to do is explain that, and I'll see the
  light!

  73 Tom


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