Grounding- What Smart Students and Electrical Engineers Are Really Being Taught

kwired

Electron manager
Location
NE Nebraska
They are, in the least the theory of the earth being a charged sink.
And with static discharges often the earth is a sink of opposite charge.

With a power system though the source is where current is trying to return to, if the system is grounded earth can possibly be in the path or one of the possible paths.
 

Dsg319

Senior Member
Location
West Virginia
Occupation
Journeyman Electrician
My favorite saying....current is inversely proportional to resistance that opposes it.

The myth of current (generated man made alternating current) taking the path of least resistance has always drove me nuts since I learned to know better.

This past Friday I was actually going to do a little bench test with notes just to show how current will take both paths inversely proportional of the different resistance values (one larger and one smaller resistor—parallel circuit)

Sadly up until now I have had no experience with resistors and bought only 25W resistors. So long story short to have high enough current to measure easily out of the mA range, I was way over 25W and I only needed up with a smoke show.......
 

mbrooke

Batteries Not Included
Location
United States
Occupation
Electricity
And with static discharges often the earth is a sink of opposite charge.

With a power system though the source is where current is trying to return to, if the system is grounded earth can possibly be in the path or one of the possible paths.

Right
 

mbrooke

Batteries Not Included
Location
United States
Occupation
Electricity
Random video in my recommendations. Same thing. Earth, ground, yada :rolleyes:




Electricity will still go through the cat- 25 ohms will not pull the voltage down at the source, appliance or trip the OCPD.
 

mbrooke

Batteries Not Included
Location
United States
Occupation
Electricity
Another one. :sick: 25 ohms is not a low impedance:



Low impedance can only be defined as a fault loop between X1 and X0 that opens a breaker within a maximum time of 0.8-0.4 seconds. Earth has no role in this process what so ever.

Also the fuse or breaker is less about overload protection, but more about removing hazardous voltage after a fault occurs.
 

romex jockey

Senior Member
Location
Vermont
By a small percentage. We live in a world with TN-C-S supplies.
(bold mine)

exactly , and our electrical theory follows suit MBrooke
consider the options>

I'll up the ante' with the notion that noodles complicate the issue>
how many MBJ's can we install under one roof? :eek:

~RJ~
 

mbrooke

Batteries Not Included
Location
United States
Occupation
Electricity
(bold mine)

exactly , and our electrical theory follows suit MBrooke
consider the options>

I'll up the ante' with the notion that noodles complicate the issue>
how many MBJ's can we install under one roof? :eek:

~RJ~

It is easier to ignore the noodles, and why in my theoretical models I tend to be done with a straight 240 volt system line in South America. Clears up the picture.

But in the end is all boils down to a single loop.
 

mbrooke

Batteries Not Included
Location
United States
Occupation
Electricity
(bold mine)

exactly , and our electrical theory follows suit MBrooke
consider the options>

I'll up the ante' with the notion that noodles complicate the issue>
how many MBJ's can we install under one roof? :eek:

~RJ~

RJ- the thing is theory, or rather truth, is no stranger to competition:



The grounding article above is merely spreading ignorance and confusion to the point that when someone like Mike speaks up his work is repudiated by default.

Mike does not come across with the image of a scientist nor has he painted himself as philanthropic much like the deceptive players perpetuating earth as a magic unicorn, or those who have re-written theory to have arcing as being the bane behind all electrical fires.

"Trusted" figures always dress and sound nice, the rest ruffed up for the enjoyment of being painted as a clown.
 

kwired

Electron manager
Location
NE Nebraska
(bold mine)

exactly , and our electrical theory follows suit MBrooke
consider the options>

I'll up the ante' with the notion that noodles complicate the issue>
how many MBJ's can we install under one roof? :eek:

~RJ~
One per separately derived system that is present or per separate service where allowed.

Neutral is nothing more than a grounded conductor, beyond the MBJ grounded conductor should be isolated (not bonded again).
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
The basic concept of SWER and using the chassis of a vehicle as part of the circuit is IMHO essentially the same.

The big difference is that soil is a poorer conductors by several orders of magnitude then the metal of a chassis. If your vehicle had a wood or fiberglass composite chassis, then even wet you wouldn't be able to use the chassis as a conductor.

The point that mbrooke is making (soil is not the place that electricity is trying to get to and soil is not part of opening OCPD) is not an absolute truth, but rather an approximation that is valid when voltage is low and 'ground' resistance is high. Make voltage high enough that the resistance of the soil can be neglected, and soil can open an OCPD. Make the resistance of your 'ground' low (metal chassis in place of soil) and your 'ground' can open an OCPD.

-Jon
 

mbrooke

Batteries Not Included
Location
United States
Occupation
Electricity
The point that mbrooke is making (soil is not the place that electricity is trying to get to and soil is not part of opening OCPD) is not an absolute truth, but rather an approximation that is valid when voltage is low and 'ground' resistance is high.

Whoa!

Not much an approximation.

A 20 amp OCPD needs at least 10-15x the handle rating to achieve a guaranteed maximum disconnection time of 0.8 second.

This requires a loop ohm between 0.6 to 0.4 ohms, even with an exceptionally "low" ground rod resistance of 5 ohms the contribution to lowering the total fault path impedance is negligible.






Make voltage high enough that the resistance of the soil can be neglected, and soil can open an OCPD. Make the resistance of your 'ground' low (metal chassis in place of soil) and your 'ground' can open an OCPD.

-Jon

Typically at 115,000 volt and above this statement just starts to hold true with some level of consistency.

High currents can eject ground rods, and those that do not cause heating around the rod whereby R goes up.

Even at 7,200 volts a 25 ohm rod will initially pass 288 amps, just approaching the ground pickup of typical feeders and the pickup of a 100K or 100T fuse (typically fuses are 220%-250% of their rating).
 

romex jockey

Senior Member
Location
Vermont
RJ- the thing is theory, or rather truth, is no stranger to competition:



The grounding article above is merely spreading ignorance and confusion to the point that when someone like Mike speaks up his work is repudiated by default.

Mike does not come across with the image of a scientist nor has he painted himself as philanthropic much like the deceptive players perpetuating earth as a magic unicorn, or those who have re-written theory to have arcing as being the bane behind all electrical fires.

"Trusted" figures always dress and sound nice, the rest ruffed up for the enjoyment of being painted as a clown.
more evidence the world is turning faster than i can keep up with MBrooke :eek: ~S~
 
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