Grounding with Surge Protection

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mbrooke

mbrooke

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Just watched this video saying grounding doesn't make a difference in surge protection or how surge protection devices operate:


I can understand this in terms of something happening on the primary side, but what if the service drop got hit by lightning or 7,200 volts touched one of the 120 volt conductors going into the building? Wouldn't the earth help in lower the impedance? They say lightning is seeking the shortest path to ground, so wouldn't good earth electrodes help?
 
You want to minimize impedance between circuit conductors, not to earth, to assure OCPD operation.

Likewise, you want to minimize voltage between conductors, not between circuit and earth, to protect equipment.
 
LarryFine said:
You want to minimize impedance between circuit conductors, not to earth, to assure OCPD operation.

Likewise, you want to minimize voltage between conductors, not between circuit and earth, to protect equipment.
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Basically bonding type theory? I still see a ground being a good thing is 7,200 volts came into the property.
 
mbrooke said:
Basically bonding type theory? I still see a ground being a good thing is 7,200 volts came into the property.
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What I'm suggesting is that, to most equipment, damage is more likely from high input voltage than high voltage to earth.
 
What does a typical electronic device with a 2-wire power supply care what the voltage to earth is (unless it's very extreme)?

Over the years, I believe I've seen more over-voltage damage from, for example, a broken neutral than from lightning strikes.
 
LarryFine said:
What does a typical electronic device with a 2-wire power supply care what the voltage to earth is (unless it's very extreme)?

Over the years, I believe I've seen more over-voltage damage from, for example, a broken neutral than from lightning strikes.
Click to expand...


Right, but imagine lightning striking the secondary service conductors, a phase specifically. It will go through the device, back on the neutral and eventually over the bonding jumper to ground.
 
mbrooke said:
Right, but imagine lightning striking the secondary service conductors, a phase specifically. It will go through the device, back on the neutral and eventually over the bonding jumper to ground.
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In that case, I can't imagine a SPD being any help to prevent damage.
 
On a lightning damaged home, it struck a tree in the yard, it was apparent the voltage difference was between the grounded conductors and the EG. Carbon tracking was very apparent in recessed cans between the screw shell of the lamp socket and a mounting screw of the socket. Would surge protectors have worked there vs more /better GES?
 
ptonsparky said:
On a lightning damaged home, it struck a tree in the yard, it was apparent the voltage difference was between the grounded conductors and the EG. Carbon tracking was very apparent in recessed cans between the screw shell of the lamp socket and a mounting screw of the socket. Would surge protectors have worked there vs more /better GES?
Click to expand...


Wondering the same lol. I'll admit surge protection is not my field of knowledge but sure is fascinating.
 
I think the point is that surge protection is helpful when it prevents the device from 'seeing' an overvoltage across any connected terminals.

If 7200V gets applied equally to both terminals of the device, then the device doesn't 'see' that overvoltage. Think 'robot bird on a wire'.

If 7200V gets applied equally to the supply terminals of the device, but the device additionally has an earth ground connection, then the device won't see a supply overvoltage, but will certainly see an insulation (to chassis/ground) system overvoltage. If a device uses ground as a signal path (eg coax with grounded external conductors) then it seems that good earth connection becomes a necessary part of surge protection.

-Jon
 
mbrooke said:
Shunting helps reduce voltage across the protected equipment, no?
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On an actual strike to the service conductors, I doubt that it really does. It will vaporize before it provides any real protection. If it is voltage from a nearby strike, it will do that as long as the energy it sees does not exceed the device rating.
 
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