[Fast Leroy]

Bingo, you have no idea how many people think ground rods will save them in a fault.

In most cases if the electricity is flowing to ground you've already had a fault. A "ground fault" is just that. The normal circuit failed, "shorted to ground" and caused the electricity to flow to ground. That's also usually when all the smoke gets out.

 

[Fast Leroy]

Ok, let’s say I have a electric motor with a fault to the frame on one of the hot legs and just a ground rod connected to the frame, not bonded. I go touch it am I live with electricity or am I safe?

If the ground rod is installed properly and the XO of the transformer is grounded the breaker will trip because all the current from the hot leg will flow to ground back to XO.

There are High Resistance Grounding systems in industrial manufacturing plants that connect the XO terminal ( center of the winding on the secondary side of the transformer) to ground through a large resistor that limits the current flow to ground in the case of a ground fault on a motor. This allows the motor to continue to run, even in a ground fault condition until repairs can be scheduled.

Here is a good link that explains it.

https://www.benderinc.com/know-how/technology/high-resistance-grounded-system-hrg

 

[Fast Leroy]

I get what your saying, no down time until maintenance, but in residential wiring earth has a high resistance not tripping the breaker, kinda like high resistance grounding.
Now if the ground rod was bonded to neutral the right way then the fault current would travel back through neutral to the source.

So the neutral is a current carrying conductor. For almost all circuits the "Hot" wire is connected to the neutral wire with a load (think air conditioner) in between. The resistance of this load is what keeps the current from from getting so high that it trips the breaker. So a "short" happens when the hot and neutral or ground gets together without the load in between.

I don't agree with your statement "but in residential wiring earth has a high resistance". There are so many factors that effect the resistance of the ground rod to ground. Normally for residential installations it should be 5 ohms or less. I suspect that in Florida or New Orleans they get close to Zero because of the water table in the ground.

 

[Fast Leroy]

I wouldn't think earth could pass enough current to trip a breaker, High resistance ,at least at low voltages 120-575.

Keep in mind that the XO of the transformer is also grounded and is at the same potential as the ground rod.

Tesla proved in the early 1900's that electrical signals could be transmitted through the ground, see Wardenclyffe Tower.

 

[Fast Leroy]

the ground rod is to form a ground field and it has a designed electrical path to dissipate a static discharge voltage. BTW, I am suffering Static problem that damages my parts in my ways. So is everyone using an anti-static soldering mat or something like that?

I use wrist grounding straps. You can also take up smoking as the carbon from the smoke that gets on your fingers will help to bleed off the static charge. IBM learned this by accident. Techs that smoked had a lower failure rate of parts from ESD and they discovered that it was because the carbon in the smoke help to discharge any static from their body.

 

[Fast Leroy]

I think IBM learned that without a resistor a wrist band can electricute a person also. No?

Never heard that, kinda defeats the purpose of "the path of least resistance"... My strap is always grounded.

 

[Fast Leroy]

I think of cow barns. A traditional cow barn the cow is tethered to the stantions. Her water bowl is supplied by iron pipe. Vacuum, milk lines touch her. She stands on a urine soaked concrete floor. Behind her is a barn cleaner. All of these conductive surfaces is connected to a power supply. The definition separating earth grounding from bonding is a bit fuzzy. All of these machines are always wet with electrolyte. Any can contribute voltage.

If the current passes through a cow she suffers.

By connecting earth electrodes to concrete reinforcing steel to electrical neutral, along with bonding all conductive items in contact with the cow, current flows through these wires, instead of the cow.

Earth electrodes are notoriously high resistance. Still they provide a path of less resistance than a human being. Without them there would always be some small potential from center tap to ground.

Excellent point. Sometimes it's easier to put everything at the same potential rather than trying to insulate one from another. Ever notice inside a large electrical substation yard at the base of a manual disconnecting switch. There is a metal pad that is bonded to the support structure that the switch is mounted on. The operator of the switch stands on the metal pad effectively placing his body at the same potential as the switch. In the case of a short of the switch and the structure becomes energized, the operator is at the same potential so no current flows through his body and he is safe.