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

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mbrooke

mbrooke

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I lost brain cells reading this article... it is just so subversively wrong, in so many ways, despite being used as a teaching resource in some schools:

Grounding: In Your Home
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Each of the electrical fixtures in your home is grounded as a safety measure. Home Tips points out that, if one of the wires in an outlet broke and touched a conductor (metal, for example), the electricity would flow and could cause a fire or electrocute a person who touched it. The ground wire in an electric outlet is a safety valve; any undesired electricity (positively charged energy) flows to the negatively charged ground, where it wants to go.
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The Electrical Path Most Traveled... or Sought
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Electric current, like water making its way down a gentle, rocky incline, always tries to take the path of least resistance. If it is impeded by a number of different of insulating materials, it will want to flow through the least-insulating (i.e., most-conducting) one. If a conductive path exists, it will always choose that path over all else.
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sciencing.com

Why Does Electricity Go to the Ground?

Even though lightning has been understood by science for quite some time, it’s hard not to feel a bit of primal fear when watching those bright bolts split the sky. Lightning, of course, is actually a quick burst of electricity.
sciencing.com sciencing.com

The whole article makes it sound as though if I attached a ground wire to my leg I could safely touch a high voltage line with my bare hands because the earth would prevent electrons from "building up" in my body. Ignoring the fact current flow through a resistance generates heat as its heading back to the wait for it... SOURCE. Not ground.

This is why Engineers leave school saying electrons seek the shortest path to ground or that the earth is an electron sink.


This is also why I'm hitting the concept of grounding and bonding so hard as of late, and why I want to do away with the terms "grounding" and "bonding" instead replacing them with "source conduction" "fault loop impedance" and "automatic disconnection of supply"

What makes this a particularly rocky endeavor being these views are held by universities and some code making panel members.

What do others make of all this?
 
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The simplest explanation* is that an EGC allows an OCPD to react to a line-to-enclosure fault as it would a line-to-neutral fault.

The only reason current tends to flow into the earth is because we intentionally earth one of the system conductors.


*Using our terms, though.
 
LarryFine said:
The simplest explanation* is that an EGC allows an OCPD to react to a line-to-enclosure fault as it would a line-to-neutral fault.

The only reason current tends to flow into the earth is because we intentionally earth one of the system conductors.


*Using our terms, though.
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Tends?

With a 0.02 ohm service neutral and a 25 ohm ground rod at the house + 25 ohm rod at the pole, at least 196 amps will be flowing on the service neutral.

This is why I want ground (terra firma) completely removed from the equations.
 
mbrooke said:
Tends?

With a 0.02 ohm service neutral and a 25 ohm ground rod at the house + 25 ohm rod at the pole, at least 196 amps will be flowing on the service neutral.

This is why I want ground (terra firma) completely removed from the equations.
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I was referring to people getting shocks.
 
LarryFine said:
I was referring to people getting shocks.
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Ground can be one pathway back to the source, as well as extraneous conductive objects in contact with the earth or bonded to the service neutral so they do not remain live should a fault occur to them such as rebar, pipes, exposed metal or appliances/switches/conduit/ect.
 
Are engineering schools actually using this as part of their teaching though?

It isn't too bad for young kids other than the "in the home" section. Particularly when explaining lightning or other static charges.
 
kwired said:
Are engineering schools actually using this as part of their teaching though?

It isn't too bad for young kids other than the "in the home" section. Particularly when explaining lightning or other static charges.
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They are, in the least the theory of the earth being a charged sink.
 
I didn't see much that was so objectionable or mind numbing about the article that was linked. It's clearly not meant to educate engineers or electricians and shouldn't be judged that way. There are some terms that one could quibble with if the audience was people trained in the electrical industry, but that's not the target audience. This is one example that could use some cleaning up....

Grounding: In Your Home
Each of the electrical fixtures in your home is grounded as a safety measure. Home Tips points out that, if one of the wires in an outlet broke and touched a conductor (metal, for example), the electricity would flow and could cause a fire or electrocute a person who touched it. The ground wire in an electric outlet is a safety valve; any undesired electricity (positively charged energy) flows to the negatively charged ground, where it wants to go.

Leave out the part about negative charged ground and you have a basic explanation of how an equipment grounding conductor works.

If you are trying to explain how a circuit breaker and equipment grounding conductor works to someone who has no understanding of electrical systems this explanation isn't so bad

The Three-Pronged Plug
In household settings, grounding treats both the "symptom" and the "disease" in the event of an unanticipated accumulation of charges on the surfaces of appliances. It not only allows the rogue charges an immediate "one-way" exit so they can disperse elsewhere, but it also prevents the entry of more unwanted charges by interrupting the circuit "upstream."

A typical modern outlet has three holes: two side-by-side slits and an almost-round aperture beneath. The smaller vertical slit is for the "hot" wire (or literally, plug component) for incoming current; its longer partner is for the neutral (exit) wire. The round plug is a ground wire connected straight to an exit from the circuit, so dangerous charges that would otherwise flow along the surface of an appliance can flee for the ground. This wire is set up so that above a given current level, the entire circuit is broken and all incoming current stops.
 
Problem is electricity doesn't head to ground during a fault. Nor does electricity choose the path of least resistance. Target audience is left with the wrong seeds none the less.
 
mbrooke said:
Problem is electricity doesn't head to ground during a fault.
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Yes it does. We live in a world with a grounded system.
Nor does electricity choose the path of least resistance.
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Yes it does. It takes all paths and the majority of it follows the path with the least resistance. Why else would we need to worry about EGC circuits being a low resistance fault path?
Target audience is left with the wrong seeds none the less.
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They are left with a very basic understanding of electrical and if they pursue further education they will learn more particular information that is important to those that work in the electrical field but matters little to anyone else.
 
ActionDave said:
The Three-Pronged Plug
In household settings, grounding treats both the "symptom" and the "disease" in the event of an unanticipated accumulation of charges on the surfaces of appliances. It not only allows the rogue charges an immediate "one-way" exit so they can disperse elsewhere, but it also prevents the entry of more unwanted charges by interrupting the circuit "upstream."...
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This sounds curiously like an explanation of how to do something in New Math. Why can't they just say "The three pronged plug prevents, in the event of a malfunction, voltage from being present the outside of an electrical device which can cause the person touching it to receive a shock, possibly serious enough to cause death".

-Hal
 
ActionDave said:
Yes it does. We live in a world with a grounded system.
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By a small percentage. We live in a world with TN-C-S supplies. 0.02 ohm neutral with a 25 ohm grounding electrode system. The ground simple does not facilitate in opening a breaker. Its not fair to emphaisis current heading toward earth when the earth does not do any work opening a breaker.

Yes it does. It takes all paths and the majority of it follows the path with the least resistance. Why else would we need to worry about EGC circuits being a low resistance fault path?
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Saying it takes the path of least resistance or "it will always chose the path over all else" is very different from taking all paths.

They are left with a very basic understanding of electrical and if they pursue further education they will learn more particular information that is important to those that work in the electrical field but matters little to anyone else.
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This article isn't even correct from a basic understanding sense. It is wishful thinking to assume those pursing engineering or the trade will learn the correct information or bother re-learning an already cemented foundation.

Case in point: Trailer in Iraq kills soldier due to an open EGC coupled with a faulty water pump. EEs come in wanting to drive ground rods. Where did they get that idea?
 
mbrooke said:
Case in point: Trailer in Iraq kills soldier due to an open EGC coupled with a faulty water pump. EEs come in wanting to drive ground rods. Where did they get that idea?
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I don't know. I have no formal education in anything electrical which is why I refer to myself as a wire pulling grunt.

I'm the one who coined the term Dirt Worshipers on this forum many years ago and I have derided them and the mentality they represent for as long as I have been an electrician. But don't insist a web site that is directed at an elementary school audience is subversively corrupting electrical engineering. Like I said, overall, I think the site is good. I'd give it a B.
 
ActionDave said:
I don't know. I have no formal education in anything electrical which is why I refer to myself as a wire pulling grunt.

I'm the one who coined the term Dirt Worshipers on this forum many years ago and I have derided them and the mentality they represent for as long as I have been an electrician. But don't insist a web site that is directed at an elementary school audience is subversively corrupting electrical engineering. Like I said, overall, I think the site is good. I'd give it a B.
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You know more than they do. :) I've spoken to college grades who've said the exact same thing word for word, some on forums like these.

I insist it is part of the problem, particularly when laying the foundation of what will be future citizens, DIYs, and of course trades men. Less worry about trades men in that of course most will figure out otherwise in today's world.

I'm well aware that it is not fair to place blame solely on this article being one out of perhaps hundreds of thousands insinuating ground clears breakers, however it still exists.

It might get a B for effort and sounding professional, however when I was in school if I submitted anything false it was either a D or an F being at least 1/3 of the grading criteria. Educators meant bussiness.
 
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