POLEpig

Thread Starter

na5m

Joined Jul 19, 2012
14
To what does the other end of the primary side of a residential step-down transformer
get connected to? Obviously, one end of the primary is connected
to the high-voltage distribution line. The other end I don't really know
where it goes

 

t_n_k

Joined Mar 6, 2009
5,455
In a 3 wire distribution system the obvious connection for the primary of a single phase transformer would be between any two phases.
 

gerty

Joined Aug 30, 2007
1,305
Around here we have the 3 phases running on crossbars on the pole and a grounded neutral running below them. Each residential transformer drop is tied from a phase to this neutral.
 
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PackratKing

Joined Jul 13, 2008
847
I can't speak to 3-phase due to insufficient experience........

In residential 240, where the bus bars are 180° apart regarding phase, providing either 120 or 240vac.

As wired to normal household outlets, you would hook one transformer primary lead ---- Via a switch and fuse or circuit breaker to the hot [ black ] lead and the other lead to neutral, which in some places is also run to earth ground....

If you have a transformer rated for 240, ----- Via a properly wired outlet and a plug intended for 240 applications, such as a clothes-dryer receptacle.
You would connect one primary lead to each hot line, with your primary center-tap if present -- to neutral, or to earth ground.
The item so powered demanding a switch, DPDT that will break both hot leads simultaneously, and fuse or circuit breaker on each leg.
 
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#12

Joined Nov 30, 2010
18,224
At my house, the local transformer is fed from a kilovolt line and it must be using a neutral wire or an earth ground. I can tell because only one energized wire is approching and it has 2-disk insulators.
 

gerty

Joined Aug 30, 2007
1,305
At my house, the local transformer is fed from a kilovolt line and it must be using a neutral wire or an earth ground. I can tell because only one energized wire is approching and it has 2-disk insulators.
I'll bet if you look around the pole you'll see a bare copper wire about a #6 stapled to the pole and going down into the ground.
 

#12

Joined Nov 30, 2010
18,224
There is a bare wire coming from another pole but I don't know if that is the ground because I'm too lazy to walk over there and look. Point is: some local transformers are not fed from 2 phases of a 3 phase supply.
 

Thread Starter

na5m

Joined Jul 19, 2012
14
The conductor that I have dotted in red, where is it physically located?
I can see the three high-voltage phase conductors up on the power pole, but
it looks like this neutral conductor dives into the ground at the base of the power pole
in my neighborhood.

THANKS for all the replies!

 

#12

Joined Nov 30, 2010
18,224
That's because it IS ground.
One of those dots is inside a transformer. The rest are called, "neutral" by electricians.
 

Thread Starter

na5m

Joined Jul 19, 2012
14
The conductor I have highlighted in red, can it be strung
above ground on the pole, or, alternatively, laid underground?
In the following picture, it seems that the power company
has placed this conductor underground because there is a
conductor running down the pole and disappearing into the
earth.


.
 

#12

Joined Nov 30, 2010
18,224
No. The red line is a wire that is CONNECTED to terra firma.

Are you having trouble with Ground = neutral = earth = terra firma?
 

Thread Starter

na5m

Joined Jul 19, 2012
14
So from the ground (terra firma), how does the current get back to the generating station & complete its circuit? Does it behave like SWER?
Like in my revised picture below?



Thanks for all your helpful answers.
 

#12

Joined Nov 30, 2010
18,224
The current travels on a grounded conductor called a wire to get back to the generating section. The local ground is just a safety ground, not a current carrying ground. The red wires you put in that last drawing forgot to include the current carrying neutral wire.
 

Thread Starter

na5m

Joined Jul 19, 2012
14
The current travels on a grounded conductor called a wire to get back to the generating section. The local ground is just a safety ground, not a current carrying ground. The red wires you put in that last drawing forgot to include the current carrying neutral wire.
So you're saying that there is a neutral wire returning to the power generator, like in the below picture?

 
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