This is not true in Europe and any attempt to ground the incoming line will result in disaster.

In many parts of the rest of the world, the neutral is a star point of a 3ph transformer and is earth grounded and the 240v 1ph supply is one of the phases.
It is also grounded again at the service entry.
Max.

 

It is also grounded again at the service entry.

Yes to most of what you have said, by most definitely no to this.

 

Woah there, that description could lead to a serious bang in many countries.

In the United states there is a transformer between you and the incoming hot wires from the supplier.

This is not true in Europe and any attempt to ground the incoming line will result in disaster.

Not at all. Any one point may be grounded on most any separately derived system.

 

Thanks for the help, everyone. I still need some clarification though. If for instance the main breaker panel was not grounded...a ground fault would still find a path to ground through the ground conductor, into the panel ground bar, which is connected to the neutral terminal which is grounded at the meter. So is the ground at the panel just a redundancy? Is it required by code? Are two ground connections required (water inlet piping, and ground rod)?

In a perfect world where wiring/connections never fail, never leak, and are zero ohms from point to point at any current level it might be redundant. What's code depends on your location but for many reasons already talked about having a separate grounding system just for your electrical circuits is a very good idea.

Just earth grounding to internal water pipes is no longer good practice as more utilities are using PEX or other types of none-conductive piping from feeders. Any internal metal framing or piping should still be grounded for electrical safety. A external grounding system using rods, mesh or plates bonded to the main ground connection is better.

http://inspectapedia.com/electric/0533s.jpg

 

Not at all. Any one point may be grounded on most any separately derived system.

Perhaps you would like to quote from the European wiring regulations that allow this?

In Europe it is illegal to ground the neutral.

In the USA it is illegal not to.

This is a safety issue, so posts should be more considered.

The underlying fact is that word neutral is referring to different things in each system.

 

When I covered my Electrical education in UK, the practice was to ground the neutral star point at the supply transformer but although the neutral was not allowed to contact the neutral at the service entry, a ground had to be set up and the required ground resistance had to be measured back to the grounded star point in order to comply with a maximum allowed reading.
This also applied to Australia and a few other countries I do not have at hand
It has been many years since I practiced there so I assume it could have changed?
But AFAIK the grounded neutral still applies.
Max.

 

INWO: So the connection from the panel to the water inlet pipe is to ground the piping system rather than the reverse?

It depends.

If water supply is metallic (cu.), it makes an excellent ground point.

Either way, any exposed metallic material in the home must be bonded to system ground/neutral.

There some dispute over gas lines. For electrical safety it must be bonded. For other reasons it's a bad idea. Inspectors general look the other way.

Think, equi-potential system. Like in a swimming pool area or barnyard, if everything is bonded together, shock hazard is reduced. Even the concrete is bonded.

This is now an approved grounding electrode in nec. Concrete encased cu. wire.

 

It has been mentioned by more than one person in this thread, that the ground connection -- particularly the one at the utility pole -- is not required for the circuit, and is there for safety purposes only. I am getting contradictory information that indicated that the connection to ground is absolutely essential to the circuit as the 120V is relative to earth (ground) which is neutral or zero volts.

 

. I am getting contradictory information that indicated that the connection to ground is absolutely essential to the circuit as the 120V is relative to earth (ground) which is neutral or zero volts.

As I mentioned earlier, you can take the grounding out of the equation and not notice any difference whatsoever.
Apart from the safety aspect of course.
If you refer to the first link again, it shows actually using the earth ground as a main conductor, this was done just for explanatory purposes and maybe clouds the issue for you.
Used just to show how the earth can be used as a conductor in theory only.
Max.

 

I understand that you can take the "ground" conductor out of the equation, but that is only because the neutral is also grounded at some point. The hot lines that enter the house are at 120V relative to ground, so they require a connection to ground in order to produce the full 120V potential. That is why the neutral (Center Terminal) on the transformer is connected to ground. Where am I wrong?

 

The supplier provides two conductors, electrically isolated from each other and from ground.

The supplier maintains one of these near ground potential by connecting his end, which may be miles away, to ground. He doesn't have to but there are good reasons for this grounding by the supplier.

He calls this the supplier neutral

The second conductor he maintains at a more or less fixed potential above his neutral.

He calls this the supplier line.

Apart from a few relic supplies these two conductors are all that are needed to provide the electricity supply (for single phase).

No earth is actually necessary and is still not used in some countries (eg large parts of France and Spain).

What happens when these two lines reach the consumer varies from country to country. See my sketch.

The USA system is superior.

 

As I understand it for residential wiring in the US, the two wires provided by the utility are both at 120V relative to ground. They are simply 180 degrees out of phase with one another so that when a circuit is made between both of them, you get a 240V circuit. When connection is made from either one of them to the neutral conductor, you get a 120V circuit. The neutral (CT) appears only at the residential transformer where the voltage is stepped down to 120V. As far as I can tell this Neutral conductor gets its neutrality from being connected to ground at the utility pole. This is because ground or earth, is neutral. The 120V supply lines are only 120V with respect to this neutral grounding. No?

 

The supplier provides two conductors, electrically isolated from each other and from ground.

The supplier maintains one of these near ground potential by connecting his end, which may be miles away, to ground. He doesn't have to but there are good reasons for this grounding by the supplier.

He calls this the supplier neutral

The second conductor he maintains at a more or less fixed potential above his neutral.

He calls this the supplier line.

.

There appears to be some contradictions here?
If I read this right, one conductor, the neutral is still grounded at the supply transformer, presumably the star point .
And if presumably UK installations still include 3 conductor outlet, 240v, neutral and ground?
If so, then how is the local ground pin referenced to ground?
If no ground pin, then what would be the purpose of grounding the neutral at the supply?
Max.

 

Sally, let's take this a bit at a time.
We haven't come to grounding yet.

Still concentrating on the two supply conductors.

Remember two conductors and no earth will work.
But there are safety issues with this.

In the USA much (most?) of the supplies are transmitted overhead.

In Europe much (most) of the supplies are underground.

That means it is difficult for the supply company to provide a reliable earth/ ground to each consumer in the USA, but very easy in Europe.

So in the USA an indirect supply system was adopted.
The consumer is not directly connected to the suppliers line or neutral.

In Europe the consumer is connected directly to the suppliers neutral and the suppliers line.
In fact many consumers are connected to the same line and neutral, so the possibility of local interference often occurs.

So in Europe the suppliers neutral and the consumers neutral are the same.
But in the USA the suppliers neutral is different (and electrically isolated from)from the consumers neutral.

This also applies to the line.

Are you with me so far?

 

The center tap of your local transformer is not neutral because it is connected to the planet. It is neutral because it is the center tap of the transformer. If you never connected it to Earth, it would still be neutral and an important current carrying wire for each of the 120 volt phases.

Now...if you notice that static electricity is building up on the secondary winding of the local transformer, especially during stormy weather, you provide a leakage path to ground. An 8 foot metal rod driven into the dirt will provide enough leakage to keep static charges neutralized. Half the time, it isn't really a good enough ground to short out the transformer if you jammed a 120 volt wire into the ground a hundred feet away, but it's good enough to keep from getting nasty surprises when you touch an appliance in your kitchen.

 

studiot: in the US the two supply lines that come to the meter of a house are not as you claim. Instead, they are both at 120V. I agree you can use these two conductors without a ground connection to create a circuit, albeit an unsafe one. However, that will only work for a 240V circuit, since the two supply lines are both 120V in opposing phase. in order to get a 120V circuit don't you need a connection to ground. If not, can someone please explain the path for this 120V circuit?

 

studiot: in the US the two supply lines that come to the meter of a house are not as you claim. Instead, they are both at 120V. I agree you can use these two conductors without a ground connection to create a circuit, albeit an unsafe one. However, that will only work for a 240V circuit, since the two supply lines are both 120V in opposing phase. in order to get a 120V circuit don't you need a connection to ground. If not, can someone please explain the path for this 120V circuit?

Sally, please try to follow the description, rather than argue.

If, as you say, both lines are at 120 volts then there is zero voltage between them so they cannot be used as a source of electrical energy. That is nonsense.

You do not 'see' the two supply lines provided by the power company.
You 'see' the three lines provided on the secondary side of your consumer transformer.

We have discussed this many times in this forum and what I am explaining here has been explained many times by US electricans.

All we need to proceed is to know that you understand that in the USA the neutral you see in your domestic wiring is electrically isolated from and not the same as the supply company's return neutral.

We can then discuss in detail the (very good) reasons for this.

 

I have explained it several times in this thread. The neutral wire is connected to the center of the secondary winding of the local power transformer. It would work if you never connected it to the planet.

When you get done not paying attention to this, I will be helping somebody else.

 

I should clarify. I'm referring to the lines AFTER the transformer. I realize that the domestic neutral conductor is not connected to the back to the utility. It is connected to ground at the pole. I have been told that this is only grounded for safety concerns, but I don't understand how a 120V circuit can be made without the neutral connecting to ground. THat is what I'm missing. How does that center tap on the transformer get its zero voltage (neutrality) from, if not from the ground connection?

 

I have explained it several times in this thread. The neutral wire is connected to the center of the secondary winding of the local power transformer. It would work if you never connected it to the planet.

When you get done not paying attention to this, I will be helping somebody else.

I appreciate that, but that doesn't explain why connecting to the center of the secondary winding on the transformer is zero volts.