Lighting/Surge protection

[kurtmccaslin]

I am building a house in the country and am looking for some advice on the installation of lightning/surge protection for some of my recently installed buried wiring.  I am planning a comprehensive automation system, so I would like to have good protection.
 
There is a meter pole about 30 feet from a water well that it serves.   I have run 500 feet of buried wire from the meter to the front gate, where I will have a camera and gate control, as well as some low voltage lighting.  My electrician is planning to install a surge protector at the meter.   He says that I can install a plug-in protector at the gate if I feel that I need one.   He says that this is a standard install.  Is this adequate?
 
I have put a conduit in the ditch to run fiber, so will not have a problem with surges on the data cable.   Just the power line.
 
 
Second question:
 
I my house will be about 100 feet from my detached garage.   Power enters the garage and then on to the house.   My electrician wants to put a surge protector where it enters the garage.   Do I need another one on the sub panel in the house?
 
I appreciate the help.
 
 
 
 
 

 

[westom]

 my house will be about 100 feet from my detached garage.   Power enters the garage and then on to the house.   My electrician wants to put a surge protector where it enters the garage.   Do I need another one on the sub panel in the house?

  Any wire that enters a structure must first connect to earth ground.  Either directly or via a protector.  Described are three structures - house, garage, and gate.  Each must be treated as if a separate structure.  Otherwise (for example) a lightning strike incoming to any structure can be a direct connection to electronics inside any other structure.
 
  That is why your telco's $multi-million computer operates without damage during every storm.  The wire between that computer and all other buildings has a surge protector at both ends.  That wire connects to earth before it enters each building.  That wire cannot connect directly.  So a protector makes that short connection to earth.
 
  A Tech Note demonstrates this solution.  In this case, two separate structures are a building and a radio tower.  Both have their own single point earth grounds.  To make those earth grounds even better, an interconnecting ground wire exists:
 
http://www.erico.com/public/library/fep/technotes/tncr002.pdf
 
  Surges (as the Tech Note demonstrates) enter on overhead or underground wires.  Every wire inside every incoming cable must connect to the single point earth ground.  Either directly or via a protector.  And that connection must be low impedance (ie 'less than 10 feet').

 

[wuench]

The grounds should ideally be connected.  If you think of a ground as a bucket and electricity is water.  In the event of a lightning strike, the bucket (ground) will "fill up" quickly.  At that point it will take the best path to the next ground.  If that is your electrical or communications wire it will take that, frying everything along the way.  If, however you have the grounds tied together directly, it will follow that path instead.  The more and better grounds you have the more electricity can be contained before it starts hunting for the next ground.  Better grounds are deeper, surrounded by more soil (not concrete) etc. 
 
Same is true for phone, satellite, etc on a single structure.  If one gets hit it will go to it's ground, fill up, and look for the next.  If the best path to the next ground is into your house and through some equipment, that's the path it will take.

 

[Del91574]

Actually the above is missing a key point and the bucket analogy isn't really correct.

The reason why grounds should always be tied together is to keep all the attached equipment at the same potential, not because one ground is better or worse or "fills" up. Ground is always ground, the only difference is the potential between the attached equipment and the respective ground(s) that it references (not withstanding the differences in potential between a grounding electrode and the soil)  Depth has really no bearing to how good or effective a ground functions, it's a resistance measurement that is considered. The reason why electronics fry with multiple grounds is the multiple paths to ground that are all going to be taken at the same time, then the differences in potential between the multiple ground points create voltage between them.
 
 The issue is when you introduce multiple ground references with equipment. You really don't want to create or add more grounds, unless you're referring to a ground ring or grid. Grounds are NEVER going to be in concrete or cold water piping (though it's referenced in the NEC), but electrodes in the earth itself. In the electronics world, the problem is when you have interconnected systems that reference EG and have other ground references present, that is what creates the electrical potential, which adds other issues, not just lightning and surge problems.

 

[westom]

The grounds should ideally be connected.  If you think of a ground as a bucket and electricity is water.  In the event of a lightning strike, the bucket (ground) will "fill up" quickly.  At that point it will take the best path to the next ground.  If that is your electrical or communications wire it will take that, frying everything along the way.  If, however you have the grounds tied together directly, it will follow that path instead. 

 
That describes one reason for damage in simplistic terms.  However water is so different from electricity that some concepts are (unfortunately) misunderstood when using the 'water' similarity.   Those electrical concepts (explained by using water)  that summarize a need for single point ground are 'conductivity' and 'equipotential'.  Do both because neither is sufficient.
 
  BTW, a best earth ground is inside concrete.  Surge protection is often best installed when the footing are poured.  Better equipotential and conductivity.  This earth ground was first demonstrated in munitions dumps where direct lightning strikes must never cause damage.  A concrete encased earthed ground is called an Ufer ground.  A radio station used a variation of this concept to avert damage:
    http://scott-inc.com/html/ufer.htm
The tech note  (http://www.erico.com...tes/tncr002.pdf) also demonstrates better conductivity and equipotential.

 

[wuench]

That is what I have been told by my power engineering friends as well.  I have seen data centers and satellite enclosures built that way, copper mesh embedded in or applied on top of the foundation and connected to several earth grounds surrounding the bulding.
 
But just to clarify, my point about concrete was more about not sinking a grounding rod next to a concrete foundation.  It is better to sink it away from the foundation so you have a "bigger bucket".  Concrete itself is not as good a conductor as earth.  

 

[Neurorad]

Do most commercial buildings have Ufer grounds, or do they mostly rely on SPDs?
 
To provide a single ground to those 3 buildings, I think you would need to connect them with AWG 10 or AWG 8 solid copper, which may be price prohibitive.

 

[wuench]

You might be able to do it with aluminum, as long as it provides a better path than any other connections.  That probably where the real engineering starts (of which I am not)...
 
And I think I am going to switch my electricity and networking analogies from using water to using beer from now on... 

 

[Del91574]

Commercial buildings don't have Ufer grounds....it's a specialized item. 
 
If you're running on the same electrical service, the buildings are effectively bonded to each other on the neutral bus bar and technically that is connected to EG also.

 

[archstenton]

I'm not an electrician, but I think just about every new building construction I've done, electrical engineer always seems to be confirming with me, OK to tie to my column and then run a bunch of wire through my grade beams, footings, mats, etc.(i.e. Ufer?)
 
Is it just an arid California method?
 

Commercial buildings don't have Ufer grounds....it's a specialized item. 

 

[Del91574]

Usually a local code or building conditional item to form a ground ring or grid, all the projects I'm involved in at the moment (including a very large scale medical complex and related genome research facility) has grounding electrodes driven and tied to building steel, as well as before the disconnects and almost every building I can think of with large vaults and similar is done in the same basic way. I'm thinking it's something to do with SOP's within your area.
 
Are you sure you're thinking about grounding vs. bonding?
 
Usually there is an exothermic weld between the electrode(s) and the grounding conductors that is then brought through concrete, but there's still some form of grounding electrode.

 

[kurtmccaslin]

Thanks for the valuable advice.   I have been lurking at this site for several years now, and reading, learning, reading.   Unfortunately don't have a lot to contribute.   I am just starting the building process now and hope to be able to share some experiences as I go forward.
 
What I understand is for the gate and well which are 500 ft apart, I should have a surge protector and earth ground at both places.   I will connect the surge protectors to each ground and to a buried ground wire between both sites (I already have 2 conductors plus ground in conduit between the two locations, and will use the #10 ground wire to connect them)
 
For the house and garage located 100 feet apart, I should have a surge protector at the main panel on each structure.   It will be connected to an earth ground within 10 feet of the surge protector.  There will be a buried ground conductor that connects the ground in both panels together.   I will also ask my builder about a Ufer ground.
 
Did I miss anything?

 

[pete_c]

I am a bit into weather such that I added a "lightning" sensor to my weather station.  Simple device which uses a counter to measure lightning strikes and rates.  Not sure how accurate it is but it does let me know a bit how much lightning is around. 
 
http://www.carterlake.org/lightningdetector_1-wire.php
 
Some of the higher end surge protectors also have outputs for an alarm panel. 
 
That said I have one and use a wireless switch for it.
 
A side anecdote; my uncle now in his 80's has been struck by lightning 3 times in his life; only burned his shoes all three times.
 

The expression "Lightning never strikes twice (in the same place)" is similar to "Opportunity never knocks twice" in the vein of a "once in a lifetime" opportunity, i.e., something that is generally considered improbable. Lightning occurs frequently and more so in specific areas. Since various factors alter the probability of strikes at any given location, repeat lightning strikes have a very low probability (but are not impossible).[102][103] Similarly, "A bolt from the blue" refers to something totally unexpected.

 
http://en.wikipedia.org/wiki/Lightning

 

[Neurorad]

OP, you didn't specify what size cables, between structures. As DEL alluded, you may not need that 10 AWG ground.

I think you should hire a pro, either an electrical engineer, or an experienced electrician, to help specify.

 

[westom]

OP, you didn't specify what size cables, between structures. 

 
  Thickness (gauge) of that wire, as defined by safety codes, will be sufficient.  National Electrical code defines human safety.  Grounding, for protection, both meets and exceeds what code requires.
 
  Best earthing (ie Ufer grounds, loop around a building) are best installed when the footing are poured. Best electrical connections (ie interconnecting rebar) is best done by cadwelding.