neutral current

[bond]

I understand that the unbalanced current returns to the transformer via the grounded conductor(neutral) but where does it go after that , is it recycled somehow? in the secondary. does it go to earth at the pole? what about transformers inside of buildings? where does all that fault current go?if there is one. One more thing tom baker if your reading this, I heard that in order to become an electrician in washington you need a thousand hours in commercial,industrial as well as residential unlike here in NewEngland, the funny thing is our liscence, when I get it reciprocates with washington. I plan to maybe move to WA but feel I would look like a dummy seeing all I know is residential here in MA.How is the employment outlook for residential? Should I get some comm,industrial experience before moving out there? Thank You...

 

[charlie b]

Re: neutral current

Originally posted by bond: I understand that the unbalanced current returns to the transformer via the grounded conductor(neutral) but where does it go after that , is it recycled somehow? in the secondary. does it go to earth at the pole?

Good question. The answers are (in order) ?Yes? and ?No.? The current goes into the neutral (i.e., the center point of the WYE), then passes through the secondary windings, and travels back along the ?hot? wire to the load (or to the fault point). It continues in this circular path forever (or until you turn off the load, or until the breaker trips on the fault current). So, ?Yes,? it is recycled, and ?No,? it doesn?t go to Earth.

 

[bennie]

Re: neutral current

Bond: Fault and load current does flow in the earth but does not dissipate in the earth like static charges.

 

[Ed MacLaren]

Re: neutral current

Bond,
The primary and secondary currents of a common transformer (not autotransformer) are completely separated, and do not mix.

This sketch shows a simple single phase transformer, for example, a control transformer.


Same in an AC system, except they reverse direction 120 times a second.

Ed

 

[bennie]

Re: neutral current

Hello Ed: What happens when there is a high side to low side fault in the windings?

 

[Ed MacLaren]

Re: neutral current

What happens when there is a high side to low side fault in the windings?

I don't know, Bennie, what do you think will happen?

Here is the same transformer, showing a primary supply circuit.

Ed

 

[hurk27]

Re: neutral current

By Bennie: What happens when there is a high side to low side fault in the windings?

I would think there would be a less of a load on the low side afterward LOL

While in HV transformers the low side would have a much heavier coil and probably fault the primary OCPD but not always. in a class 2 type transformer it will probably blow the winding open and if the load has any reference to ground or neutral it will burn up the load too. It all depends on how the fault shorts to the low side.

 

[pierre]

Re: neutral current

My thoughts are the high side OCPD would open, possibly both sides would open.
Don't keep us waiting too long Bennie

Pierre

 

[bennie]

Re: neutral current

Change the primary voltage to 7.2 KV. Feature a winding to winding fault. 7.2 KV will appear on the secondary until the primary cut out activates.

This is the basic function of the MGN system. The shorting effect on the low side will permit the fault to clear.

 

[Ed MacLaren]

Re: neutral current

7.2 KV will appear on the secondary until the primary cut out activates.
This is the basic function of the MGN system.

Are you saying the earth grounding system will blow the primary fuse at that voltage?

I was under the impression that the two windings were "ground-tied" to ensure that the primary fuse opened in the event of a winding-to-winding fault?

Ed

 

[bennie]

Re: neutral current

The MGN is connected to both the high and low side to protect against high voltage appearing on conductive grounded surfaces.

This is why the secondary and primary must be electrically connected by a grounded conductor.

Earth connection is not a factor.

[ March 01, 2004, 05:49 PM: Message edited by: bennie ]