Understanding the Role of Grounding in AC Single Phase Systems

[sophiecentaur]

The British consumer is not electrically isolated from his neighbour and what he does affects the neighbours supply.

His neighbours three doors either side of him, usually (WYE transformer). But his neutral is shared with everyone. If the neutrals and Earth's were joined at both ends, there could be some really hefty Earth currents flowing constantly from induction. It's just like a Hifi system, where you should connect all grounds to one point.

 

[Studiot]

Hello martinaston, you have pretty well confirmed what I was saying about British practice.

What do you not understand about US practice?

It is indeed a US code requirement that the consumer 'neutral' should be earthed to a local Earth at the entry point to the premises. US power companies do not provide Earth terminals, as a rule.

The transformer is often in a service cupboard these days. Formerly it was on poles.

 

[jbriggs444]

Here in the UK we now use RCD's on all new installations that trip at 30mA, not sure how the US does it ?

In the U.S. individual wall outlets are sometimes protected with "ground fault interruptors" (GFI's). You will generally find such outlets in the wash room or kitchen. There are typically two buttons on such a device. One to reset it in the event of a an accidental trip and one to test it, thereby causing it to trip.

Downstream outlets on a circuit are sometimes protected by the interruptor. An outlet will stop working and you walk into the wash room to reset the GFI.

There is a picture of a U.S. device and some additional details in the North America section of http://en.wikipedia.org/wiki/Residual-current_device.

[I am not an electrician]

 

[rollingstein]

If you call the power company concerning the 30v on your Neutral they would probably thank you because it means they are earning a fortune.

I didn't get that remark. Can someone elaborate?

 

[rollingstein]

This voltage should be fairly low and can be felt if you stick your hand between the Neutral and Earth conductors to give you a "tinkle"

Sounds like a dangerous thing to try!

 

[Studiot]

For example, a crane that was grounded to the system neutral and that contacted an energized line would expose any person in contact with the crane or its uninsulated load line to a touch potential nearly equal to the full fault voltage.

Here is an excerpt from dlgoff's link in this thread.

Note the effect of grounding the neutral.

https://www.physicsforums.com/showthread.php?p=4249959&posted=1#post4249959

 

[rollingstein]

Note the effect of grounding the neutral.

For something mobile like a crane what does "grounding the neutral" mean?

"grounded to the system neutral " to be precise.