I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

On 2/24/2012 10:14 AM, wrote:
I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

Think about it. Only one (of the two) wires feeding the primary of a
typical single phase distribution transformer needs to be insulated.

On 2/24/2012 9:14 AM, wrote:
I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

In the alley behind my house the poles have one high voltage wire
(8000V) and 3 low voltage wires (H-N-H). The low voltage H-H wires break
between transformers but the neutral is continuous. The high voltage
return must be on the secondary neutral.

--
bud--

On Feb 24, 10:28*am, George wrote:
On 2/24/2012 10:14 AM, wrote:

I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

Think about it. Only one (of the two) wires feeding the primary of a
typical single phase distribution transformer needs to be insulated.


The 3 wires you see running down the road on
poles are each one phase of a 3 phase distribution
system. They are 120deg out of phase with each
other. For larger industrial loads, like motors, they
use all 3 phases and step it down. For light loads, residential, they
use any one of the three phases
and run it into a center
tap transformer. The center tap becomes your
neutral and each of the ends becomes one of the
hots, giving you 240V between them, 120V between
each of them and neutral.

On Feb 24, 10:28*am, George wrote:
On 2/24/2012 10:14 AM, wrote:
How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

Think about it. Only one (of the two) wires feeding the primary of a
typical single phase distribution transformer needs to be insulated.

The problem is, there is only ONE wire.

On Feb 24, 10:14*am, wrote:
I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

~~ Evan

wrote in message

The problem is, there is only ONE wire.


The 2nd wire is the neutral down below. Notice this will run from pole
to pole in-between where there are not 3 wires.

The following is not exactly your transformer, but same thing...

"If a primary neutral wire is available, a 'wye' or 'phase to neutral'
transformer can be used. This usually has only one bushing on top,
connected to one of the primary phases. The other end of the primary
winding is 'grounded' to the transformer's case, which is connected to
the neutral wire"...
http://en.wikipedia.org/wiki/Distribution_transformer

On Feb 24, 10:45*am, Evan wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

On Feb 24, 10:31*am, bud-- wrote:
On 2/24/2012 9:14 AM, wrote:

I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

In the alley behind my house the poles have one high voltage wire
(8000V) and 3 low voltage wires (H-N-H). The low voltage H-H wires break
between transformers but the neutral is continuous. The high voltage
return must be on the secondary neutral.

--
bud--

I think the return path for the other side of the primary
transformer is the earth. Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. I see what the OP and you
are talking about all over here in rural NJ. You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. I believe
the other side is connected to earth ground. That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

Google "Single-wire earth return" (SWER) for a diagram and explanation - as
others have said, it uses earth grounding for the return path.

http://en.wikipedia.org/wiki/Single-wire_earth_return



wrote in message
...
On Feb 24, 10:45 am, Evan wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

SRN wrote:

Google "Single-wire earth return" (SWER) for a diagram and explanation - as
others have said, it uses earth grounding for the return path.

http://en.wikipedia.org/wiki/Single-wire_earth_return

wrote in message
...
On Feb 24, 10:45 am, Evan wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

The norm is one to three phase conductors at the top of the pole or on
the cross arm at the top of the pole, with the neutral for those on the
pole a few feet down, and the low voltage secondaries if present a few
feet below that. The neutral is grounded at least every few poles with a
small uninsulated wire down the side of the pole that connects to a
plate at the bottom of the pole underground. The SWER or delta (two
phase conductors, no neutral) configurations are obsolete and only found
in areas with old infrastructure.

On Feb 24, 3:14*pm, wrote:
I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

The neutral and the ground may be one and the same.
Common thing is Australia for example. But only in rural areas.
So the "return" current goes through the ground.
A cheap system, not without it's dangers.

On 2/24/2012 12:14 PM, harry wrote:
On Feb 24, 3:14 pm, wrote:
I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

The neutral and the ground may be one and the same.
Common thing is Australia for example. But only in rural areas.
So the "return" current goes through the ground.
A cheap system, not without it's dangers.

Some years back, I called the power company when I noticed that the
metal thieves had cut and removed the copper ground/earth wires from
all the power poles up and down the streets in my area. The wire was
cut at the point as high as a man could reach. None of the power was
of the single high voltage hot wire types. If that had been the case,
there would have been a number of two legged crispy critters littering
the downtown landscape. ^_^

TDD

On Fri, 24 Feb 2012 08:30:26 -0800 (PST), wrote:

On Feb 24, 10:45*am, Evan wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.


http://imgur.com/gFrGB

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

On Feb 24, 11:52*am, "SRN" wrote:
The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

For purposes of this discussion, you are correct. These IS another
wire somewhere. It may be running down the pole to the ground (using
the earth as most of the "wire") and may look like a steel support
cable...

On 2/24/2012 2:01 PM, Larry Fishel wrote:
On Feb 24, 11:52 am, wrote:
The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

For purposes of this discussion, you are correct. These IS another
wire somewhere. It may be running down the pole to the ground (using
the earth as most of the "wire") and may look like a steel support
cable...

In the US in a residential area, indeed.

In some (very) rural areas of Sask, CA, I saw one-line w/ earth return
as recently as roughly 20-yr ago yet...

--

harry wrote:
On Feb 24, 3:14 pm, wrote:
I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

The neutral and the ground may be one and the same.
Common thing is Australia for example. But only in rural areas.
So the "return" current goes through the ground.
A cheap system, not without it's dangers.

I was looking outside one snowy day, and I saw a tree branch fall in my
front yard with the end on fire. The branch had hit the single top wire
connecting ground.

Greg

Metspitzer wrote:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST), wrote:

On Feb 24, 10:45 am, Evan wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

http://imgur.com/gFrGB

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

I believe 7,200V is about the lowest you will find anywhere and most are
13,200V or more.

wrote:

I think the return path for the other side of the primary
transformer is the earth. Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. I see what the OP and you
are talking about all over here in rural NJ. You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. I believe
the other side is connected to earth ground. That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

pic
http://thereifixedit.files.wordpress...t-to-earth.jpg

"Pete C." wrote:
Metspitzer wrote:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST), wrote:

On Feb 24, 10:45 am, Evan wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

http://imgur.com/gFrGB

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

I believe 7,200V is about the lowest you will find anywhere and most are
13,200V or more.

I was lying in bed one day watching guys adding a new transformer outside
the window. When trying to clip the wire onto the hv wire I saw a pretty
good arc. Probably at least 3 inches. A transformer feeding the house burnt
out, so they replaced that, and added another transformer in addition to
original. Result our house had less voltage fluctuations. When young, I
used to use the shortwave radio, and ever so often, maybe twice a ay, a
horrendous arching- buzzing sound would build up and quickly stop. Lasting
3-4 seconds. I never found the source of that. Didn't sound like anything
that would be consumer generated.

Greg

On 2/24/2012 6:52 PM, gregz wrote:
"Pete wrote:
Metspitzer wrote:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST), wrote:

On Feb 24, 10:45 am, wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

http://imgur.com/gFrGBr

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

I believe 7,200V is about the lowest you will find anywhere and most are
13,200V or more.

I was lying in bed one day watching guys adding a new transformer outside
the window. When trying to clip the wire onto the hv wire I saw a pretty
good arc. Probably at least 3 inches. A transformer feeding the house burnt
out, so they replaced that, and added another transformer in addition to
original. Result our house had less voltage fluctuations. When young, I
used to use the shortwave radio, and ever so often, maybe twice a ay, a
horrendous arching- buzzing sound would build up and quickly stop. Lasting
3-4 seconds. I never found the source of that. Didn't sound like anything
that would be consumer generated.

Greg

It could have been a static discharge from your antenna if you had an
external antenna. Or it could have been a static electricity discharge
from another source, even atmospheric. Another source may have been
power company or an industrial site switching high voltage power at
certain times every day. I can remember listening to distant stations
on an AM radio in different bands and hearing a "zip..zip..zip" sound
at regular intervals.

TDD

I think the return path for the other side of the primary
transformer is the earth. *Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. *I see what the OP and you
are talking about all over here in rural NJ. *You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. *I believe
the other side is connected to earth ground. *That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

In most of North America we use a Multi Grounded Neutral (MGM). That
means that there is a neutral conductor that goes back to the source
transformer's neutral point that is grounded at multiple points along
it's route. Yes there are exceptions but they are not in common use.
The reason that system is used is because it saves a lot of money
while still providing reliable service. The neutral in most utility
distribution systems is common to both windings of the transformer.
It connects to the uninsulated stud on the transformers case which is
internally bonded to one end of the primary winding and the center of
the secondary winding. There is only one insulated connection to the
primary winding and that is the other end from the neutral
connection. The grounded stud on the case is connected to the neutral
and to ground. Since the current will flow in all pathways available
to it in proportion to the total impedance of the pathway some current
will flow via the earth on the order of a few amperes per grounding
electrode.

Here is where it gets confusing. The reason that all of those
currents do not add up to some phenomenal current flow through the
earth is that the flows from the three phases cancel each other out in
all of the common connections to the degree that the current being
drawn from the system is equal. If you ran impossibly long leads from
a three phase power analyzer what you would see across any three
consecutive transformers grounds would approach zero current. Since
no system is perfectly balanced across all three phases the current in
the neutral and the earth is never zero but if you check the current
flow in the source transformers neutral and it's grounding electrode
conductor back at the power substation you would find that it is
rather low.

So while it is true that in an MGM distribution system some of the
current is flowing through the earth the actual amperage doing that is
rather small. The earth carrying current seldom causes any problems
in systems that are maintained to the National Electrical Safety Code
standard. The biggest exception is in the animal husbandry industries
were the four footed critters that spend much of their day standing or
lying in their own rather conductive waste do often suffer ill effects
from event the small stray currents that are flowing across the
ground. When some defect in the distribution neutral raises that
current a little higher the animals suffer greatly and even die from
the effects. In dairy cows for instance it will cause a drastic
reduction in production and radical changes in the cows behavior and
temperament because the animals are in nearly constant pain.
Utilities in areas with large dairying industry. Have developed
transformers with high impedance connections to ground in order to
limit the stray current to levels that are imperceptible to the
livestock. One of the utilities in Wisconsin painted these special
transformers to look like the coloration of the locally dominant type
of dairy cow.

I hope that is helpful.

--
Tom Horne

On Fri, 24 Feb 2012 17:36:07 -0800 (PST), Tom Horne
wrote:

I think the return path for the other side of the primary
transformer is the earth. *Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. *I see what the OP and you
are talking about all over here in rural NJ. *You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. *I believe
the other side is connected to earth ground. *That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

In most of North America we use a Multi Grounded Neutral (MGM). That
means that there is a neutral conductor that goes back to the source
transformer's neutral point that is grounded at multiple points along
it's route. Yes there are exceptions but they are not in common use.
The reason that system is used is because it saves a lot of money
while still providing reliable service. The neutral in most utility
distribution systems is common to both windings of the transformer.
It connects to the uninsulated stud on the transformers case which is
internally bonded to one end of the primary winding and the center of
the secondary winding. There is only one insulated connection to the
primary winding and that is the other end from the neutral
connection. The grounded stud on the case is connected to the neutral
and to ground. Since the current will flow in all pathways available
to it in proportion to the total impedance of the pathway some current
will flow via the earth on the order of a few amperes per grounding
electrode.

Here is where it gets confusing. The reason that all of those
currents do not add up to some phenomenal current flow through the
earth is that the flows from the three phases cancel each other out in
all of the common connections to the degree that the current being
drawn from the system is equal. If you ran impossibly long leads from
a three phase power analyzer what you would see across any three
consecutive transformers grounds would approach zero current. Since
no system is perfectly balanced across all three phases the current in
the neutral and the earth is never zero but if you check the current
flow in the source transformers neutral and it's grounding electrode
conductor back at the power substation you would find that it is
rather low.

So while it is true that in an MGM distribution system some of the
current is flowing through the earth the actual amperage doing that is

Wouldn't the situation where the primary is feed by a single conductor
have the same amperage returning through the earth as supplied by the
phase conductor? I wouldn't consider that "rather small"

rather small. The earth carrying current seldom causes any problems
in systems that are maintained to the National Electrical Safety Code
standard. The biggest exception is in the animal husbandry industries
were the four footed critters that spend much of their day standing or
lying in their own rather conductive waste do often suffer ill effects
from event the small stray currents that are flowing across the
ground. When some defect in the distribution neutral raises that
current a little higher the animals suffer greatly and even die from
the effects. In dairy cows for instance it will cause a drastic
reduction in production and radical changes in the cows behavior and
temperament because the animals are in nearly constant pain.
Utilities in areas with large dairying industry. Have developed
transformers with high impedance connections to ground in order to
limit the stray current to levels that are imperceptible to the
livestock. One of the utilities in Wisconsin painted these special
transformers to look like the coloration of the locally dominant type
of dairy cow.

I hope that is helpful.

Metspitzer wrote:

On Fri, 24 Feb 2012 17:36:07 -0800 (PST), Tom Horne
wrote:

I think the return path for the other side of the primary
transformer is the earth. Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. I see what the OP and you
are talking about all over here in rural NJ. You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. I believe
the other side is connected to earth ground. That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

In most of North America we use a Multi Grounded Neutral (MGM). That
means that there is a neutral conductor that goes back to the source
transformer's neutral point that is grounded at multiple points along
it's route. Yes there are exceptions but they are not in common use.
The reason that system is used is because it saves a lot of money
while still providing reliable service. The neutral in most utility
distribution systems is common to both windings of the transformer.
It connects to the uninsulated stud on the transformers case which is
internally bonded to one end of the primary winding and the center of
the secondary winding. There is only one insulated connection to the
primary winding and that is the other end from the neutral
connection. The grounded stud on the case is connected to the neutral
and to ground. Since the current will flow in all pathways available
to it in proportion to the total impedance of the pathway some current
will flow via the earth on the order of a few amperes per grounding
electrode.

Here is where it gets confusing. The reason that all of those
currents do not add up to some phenomenal current flow through the
earth is that the flows from the three phases cancel each other out in
all of the common connections to the degree that the current being
drawn from the system is equal. If you ran impossibly long leads from
a three phase power analyzer what you would see across any three
consecutive transformers grounds would approach zero current. Since
no system is perfectly balanced across all three phases the current in
the neutral and the earth is never zero but if you check the current
flow in the source transformers neutral and it's grounding electrode
conductor back at the power substation you would find that it is
rather low.

So while it is true that in an MGM distribution system some of the
current is flowing through the earth the actual amperage doing that is

Wouldn't the situation where the primary is feed by a single conductor
have the same amperage returning through the earth as supplied by the
phase conductor? I wouldn't consider that "rather small"

Do you know what the currents are at primary voltages? Your 240V 100A
residential service is some 3.3A at the lowest 7,200V primary voltage
and something like 680mA at 35kV distribution, and that's only if it's
running at the full 100A load which it isn't ever supposed to do for
more than a few seconds.

The Daring Dufas wrote:

On 2/24/2012 6:52 PM, gregz wrote:
"Pete wrote:
Metspitzer wrote:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST), wrote:

On Feb 24, 10:45 am, wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

http://imgur.com/gFrGBr

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

I believe 7,200V is about the lowest you will find anywhere and most are
13,200V or more.

I was lying in bed one day watching guys adding a new transformer outside
the window. When trying to clip the wire onto the hv wire I saw a pretty
good arc. Probably at least 3 inches. A transformer feeding the house burnt
out, so they replaced that, and added another transformer in addition to
original. Result our house had less voltage fluctuations. When young, I
used to use the shortwave radio, and ever so often, maybe twice a ay, a
horrendous arching- buzzing sound would build up and quickly stop. Lasting
3-4 seconds. I never found the source of that. Didn't sound like anything
that would be consumer generated.

Greg

It could have been a static discharge from your antenna if you had an
external antenna. Or it could have been a static electricity discharge
from another source, even atmospheric. Another source may have been
power company or an industrial site switching high voltage power at
certain times every day. I can remember listening to distant stations
on an AM radio in different bands and hearing a "zip..zip..zip" sound
at regular intervals.

TDD

HID Street light ballast igniters are known to produce a lot of RFI when
they come on at night, and if they have a bad lamp attached they cycle
endlessly producing interference. With the switch to LED street lights
and even parking lot lights that problem should gradually become a thing
of the past.

On Feb 24, 8:52*pm, Metspitzer wrote:
On Fri, 24 Feb 2012 17:36:07 -0800 (PST), Tom Horne









wrote:
I think the return path for the other side of the primary
transformer is the earth. *Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. *I see what the OP and you
are talking about all over here in rural NJ. *You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. *I believe
the other side is connected to earth ground. *That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

In most of North America we use a Multi Grounded Neutral (MGM). *That
means that there is a neutral conductor that goes back to the source
transformer's neutral point that is grounded at multiple points along
it's route. *Yes there are exceptions but they are not in common use.
The reason that system is used is because it saves a lot of money
while still providing reliable service. *The neutral in most utility
distribution systems is common to both windings of the transformer.
It connects to the uninsulated stud on the transformers case which is
internally bonded to one end of the primary winding and the center of
the secondary winding. *There is only one insulated connection to the
primary winding and that is the other end from the neutral
connection. *The grounded stud on the case is connected to the neutral
and to ground. *Since the current will flow in all pathways available
to it in proportion to the total impedance of the pathway some current
will flow via the earth on the order of a few amperes per grounding
electrode.

Here is where it gets confusing. *The reason that all of those
currents do *not add up to some phenomenal current flow through the
earth is that the flows from the three phases cancel each other out in
all of the common connections to the degree that the current being
drawn from the system is equal. *If you ran impossibly long leads from
a three phase power analyzer what you would see across any three
consecutive transformers grounds would approach zero current. *Since
no system is perfectly balanced across all three phases the current in
the neutral and the earth is never zero but if you check the current
flow in the source transformers neutral and it's grounding electrode
conductor back at the power substation you would find that it is
rather low.

So while it is true that in an MGM distribution system some of the
current is flowing through the earth the actual amperage doing that is

Wouldn't the situation where the primary is feed by a single conductor
have the same amperage returning through the earth as supplied by the
phase conductor? * *I wouldn't consider that "rather small"







rather small. *The earth carrying current seldom causes any problems
in systems that are maintained to the National Electrical Safety Code
standard. *The biggest exception is in the animal husbandry industries
were the four footed critters that spend much of their day standing or
lying in their own rather conductive waste do often suffer ill effects
from event the small stray currents that are flowing across the
ground. *When some defect in the distribution neutral raises that
current a little higher the animals suffer greatly and even die from
the effects. *In dairy cows for instance it will cause a drastic
reduction in production and radical changes in the cows behavior and
temperament because the animals are in nearly constant pain.
Utilities in areas with large dairying industry. *Have developed
transformers with high impedance connections to ground in order to
limit the stray current to levels that are imperceptible to the
livestock. *One of the utilities in Wisconsin painted these special
transformers to look like the coloration of *the locally dominant type
of dairy cow.

I hope that is helpful.

No. Because the primary is supplied from two conductors. In a Multi
Grounded Neutral (MGM) distribution system there is a continuous
neutral conductor. It is the same neutral conductor that is part of
the low lines; that is the lines below the transformer; that supply
the individual premise wiring systems. That one conductor is serving
as the neutral for both the distribution system and the premises
wiring systems served by the transformers that are connected in
succession to each phase of the distribution. That uninsulated
conductor is grounded at intervals along it's route from the
substation transformer were the distribution current originated. In
normal operation it carries comparatively little current because of
the cancellation that occurs in the common connections. The only
current flowing on the neutral is the total difference between the
current flowing on the three phases. Not the sum mind you just the
difference. So if phase A is carrying one hundred, phase B one
hundred five, and phase C one hundred three amperes the maximum
current flowing in the neutral conductor at any given instant is five
amperes. The actual purpose that the neutral current serves is to
provide a larger number of common neutral connections in which the
currents from the three phases can cancel each other out. In any
portion of a three phase distribution system were all three phases are
not present the neutral will carry the same current as the highest
current on the one or two phases that are still present. It is only
in the three phase portion of the network that the current will cancel
out to a very small value. Once that portion of the system ties back
into the three phase portion of the network then the current averaged
from all such single phased stubs will again cancel out and the
neutral current will again be a rather small value.

--
Tom Horne

I got to admit, there is clueless, and there is clueless. This was to the
extreme.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"HeyBub" wrote in message
m...

pic
http://thereifixedit.files.wordpress...t-to-earth.jpg

On Feb 24, 8:24*pm, Tom Horne wrote:
On Feb 24, 8:52*pm, Metspitzer wrote:





On Fri, 24 Feb 2012 17:36:07 -0800 (PST), Tom Horne

wrote:
I think the return path for the other side of the primary
transformer is the earth. *Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. *I see what the OP and you
are talking about all over here in rural NJ. *You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. *I believe
the other side is connected to earth ground. *That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

In most of North America we use a Multi Grounded Neutral (MGM). *That
means that there is a neutral conductor that goes back to the source
transformer's neutral point that is grounded at multiple points along
it's route. *Yes there are exceptions but they are not in common use..
The reason that system is used is because it saves a lot of money
while still providing reliable service. *The neutral in most utility
distribution systems is common to both windings of the transformer.
It connects to the uninsulated stud on the transformers case which is
internally bonded to one end of the primary winding and the center of
the secondary winding. *There is only one insulated connection to the
primary winding and that is the other end from the neutral
connection. *The grounded stud on the case is connected to the neutral
and to ground. *Since the current will flow in all pathways available
to it in proportion to the total impedance of the pathway some current
will flow via the earth on the order of a few amperes per grounding
electrode.

Here is where it gets confusing. *The reason that all of those
currents do *not add up to some phenomenal current flow through the
earth is that the flows from the three phases cancel each other out in
all of the common connections to the degree that the current being
drawn from the system is equal. *If you ran impossibly long leads from
a three phase power analyzer what you would see across any three
consecutive transformers grounds would approach zero current. *Since
no system is perfectly balanced across all three phases the current in
the neutral and the earth is never zero but if you check the current
flow in the source transformers neutral and it's grounding electrode
conductor back at the power substation you would find that it is
rather low.

So while it is true that in an MGM distribution system some of the
current is flowing through the earth the actual amperage doing that is

Wouldn't the situation where the primary is feed by a single conductor
have the same amperage returning through the earth as supplied by the
phase conductor? * *I wouldn't consider that "rather small"

rather small. *The earth carrying current seldom causes any problems
in systems that are maintained to the National Electrical Safety Code
standard. *The biggest exception is in the animal husbandry industries
were the four footed critters that spend much of their day standing or
lying in their own rather conductive waste do often suffer ill effects
from event the small stray currents that are flowing across the
ground. *When some defect in the distribution neutral raises that
current a little higher the animals suffer greatly and even die from
the effects. *In dairy cows for instance it will cause a drastic
reduction in production and radical changes in the cows behavior and
temperament because the animals are in nearly constant pain.
Utilities in areas with large dairying industry. *Have developed
transformers with high impedance connections to ground in order to
limit the stray current to levels that are imperceptible to the
livestock. *One of the utilities in Wisconsin painted these special
transformers to look like the coloration of *the locally dominant type
of dairy cow.

I hope that is helpful.

No. *Because the primary is supplied from two conductors. * In a Multi
Grounded Neutral (MGM) distribution system there is a continuous
neutral conductor. *It is the same neutral conductor that is part of
the low lines; that is the lines below the transformer; that supply
the individual premise wiring systems. *That one conductor is serving
as the neutral for both the distribution system and the premises
wiring systems served by the transformers that are connected in
succession to each phase of the distribution. *That uninsulated
conductor is grounded at intervals along it's route from the
substation transformer were the distribution current originated. *In
normal operation it carries comparatively little current because of
the cancellation that occurs in the common connections. *The only
current flowing on the neutral is the total difference between the
current flowing on the three phases. *Not the sum mind you just the
difference. *So if phase A is carrying one hundred, phase B one
hundred five, and phase C one hundred three amperes the maximum
current flowing in the neutral conductor at any given instant is five
amperes. *The actual purpose that the neutral current serves is to
provide a larger number of common neutral connections in which the
currents from the three phases can cancel each other out. *In any
portion of a three phase distribution system were all three phases are
not present the neutral will carry the same current as the highest
current on the one or two phases that are still present. *It is only
in the three phase portion of the network that the current will cancel
out to a very small value. *Once that portion of the system ties back
into the three phase portion of the network then the current averaged
from all such single phased stubs will again cancel out and the
neutral current will again be a rather small value.

--
Tom Horne- Hide quoted text -

- Show quoted text -

Tom is correct, we have had that sort of a system here in Illinois for
at least 50 years.

On 2/24/2012 8:14 PM, Pete C. wrote:

The Daring Dufas wrote:

On 2/24/2012 6:52 PM, gregz wrote:
"Pete wrote:
Metspitzer wrote:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST), wrote:

On Feb 24, 10:45 am, wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

http://imgur.com/gFrGBr

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

I believe 7,200V is about the lowest you will find anywhere and most are
13,200V or more.

I was lying in bed one day watching guys adding a new transformer outside
the window. When trying to clip the wire onto the hv wire I saw a pretty
good arc. Probably at least 3 inches. A transformer feeding the house burnt
out, so they replaced that, and added another transformer in addition to
original. Result our house had less voltage fluctuations. When young, I
used to use the shortwave radio, and ever so often, maybe twice a ay, a
horrendous arching- buzzing sound would build up and quickly stop. Lasting
3-4 seconds. I never found the source of that. Didn't sound like anything
that would be consumer generated.

Greg

It could have been a static discharge from your antenna if you had an
external antenna. Or it could have been a static electricity discharge
from another source, even atmospheric. Another source may have been
power company or an industrial site switching high voltage power at
certain times every day. I can remember listening to distant stations
on an AM radio in different bands and hearing a "zip..zip..zip" sound
at regular intervals.

TDD

HID Street light ballast igniters are known to produce a lot of RFI when
they come on at night, and if they have a bad lamp attached they cycle
endlessly producing interference. With the switch to LED street lights
and even parking lot lights that problem should gradually become a thing
of the past.

A electrical engineer friend of mine was once the head of a power
company communications division and he told me that many complaints
of radio interference his department investigated turned out to be
caused by defective doorbell transformers.

TDD

On Feb 25, 2:24*am, Tom Horne wrote:
On Feb 24, 8:52*pm, Metspitzer wrote:



*The only
current flowing on the neutral is the total difference between the
current flowing on the three phases. *Not the sum mind you just the
difference. *So if phase A is carrying one hundred, phase B one
hundred five, and phase C one hundred three amperes the maximum
current flowing in the neutral conductor at any given instant is five
amperes. *The actual purpose that the neutral current serves is to
provide a larger number of common neutral connections in which the
currents from the three phases can cancel each other out. *In any
portion of a three phase distribution system were all three phases are
not present the neutral will carry the same current as the highest
current on the one or two phases that are still present. *It is only
in the three phase portion of the network that the current will cancel
out to a very small value. *Once that portion of the system ties back
into the three phase portion of the network then the current averaged
from all such single phased stubs will again cancel out and the
neutral current will again be a rather small value.

--
Tom Horne- Hide quoted text -

- Show quoted text -

That is not true. The neutral current is the vector sum of the phase
currents, not the numerical difference.

"HeyBub" wrote in
m:

wrote:

I think the return path for the other side of the primary
transformer is the earth. Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. I see what the OP and you
are talking about all over here in rural NJ. You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. I believe
the other side is connected to earth ground. That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

pic
http://thereifixedit.files.wordpress...ash-repairs-wh
at-i-grounded-it-to-earth.jpg



Thaks for that safety tip. I need to upgrade to the pic level.

On Feb 24, 9:24*pm, Tom Horne wrote:
On Feb 24, 8:52*pm, Metspitzer wrote:





On Fri, 24 Feb 2012 17:36:07 -0800 (PST), Tom Horne

wrote:
I think the return path for the other side of the primary
transformer is the earth. *Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. *I see what the OP and you
are talking about all over here in rural NJ. *You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. *I believe
the other side is connected to earth ground. *That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

In most of North America we use a Multi Grounded Neutral (MGM). *That
means that there is a neutral conductor that goes back to the source
transformer's neutral point that is grounded at multiple points along
it's route. *Yes there are exceptions but they are not in common use..
The reason that system is used is because it saves a lot of money
while still providing reliable service. *The neutral in most utility
distribution systems is common to both windings of the transformer.
It connects to the uninsulated stud on the transformers case which is
internally bonded to one end of the primary winding and the center of
the secondary winding. *There is only one insulated connection to the
primary winding and that is the other end from the neutral
connection. *The grounded stud on the case is connected to the neutral
and to ground. *Since the current will flow in all pathways available
to it in proportion to the total impedance of the pathway some current
will flow via the earth on the order of a few amperes per grounding
electrode.

Here is where it gets confusing. *The reason that all of those
currents do *not add up to some phenomenal current flow through the
earth is that the flows from the three phases cancel each other out in
all of the common connections to the degree that the current being
drawn from the system is equal. *If you ran impossibly long leads from
a three phase power analyzer what you would see across any three
consecutive transformers grounds would approach zero current. *Since
no system is perfectly balanced across all three phases the current in
the neutral and the earth is never zero but if you check the current
flow in the source transformers neutral and it's grounding electrode
conductor back at the power substation you would find that it is
rather low.

So while it is true that in an MGM distribution system some of the
current is flowing through the earth the actual amperage doing that is

Wouldn't the situation where the primary is feed by a single conductor
have the same amperage returning through the earth as supplied by the
phase conductor? * *I wouldn't consider that "rather small"

rather small. *The earth carrying current seldom causes any problems
in systems that are maintained to the National Electrical Safety Code
standard. *The biggest exception is in the animal husbandry industries
were the four footed critters that spend much of their day standing or
lying in their own rather conductive waste do often suffer ill effects
from event the small stray currents that are flowing across the
ground. *When some defect in the distribution neutral raises that
current a little higher the animals suffer greatly and even die from
the effects. *In dairy cows for instance it will cause a drastic
reduction in production and radical changes in the cows behavior and
temperament because the animals are in nearly constant pain.
Utilities in areas with large dairying industry. *Have developed
transformers with high impedance connections to ground in order to
limit the stray current to levels that are imperceptible to the
livestock. *One of the utilities in Wisconsin painted these special
transformers to look like the coloration of *the locally dominant type
of dairy cow.

I hope that is helpful.

No. *Because the primary is supplied from two conductors. * In a Multi
Grounded Neutral (MGM) distribution system there is a continuous
neutral conductor. *It is the same neutral conductor that is part of
the low lines; that is the lines below the transformer; that supply
the individual premise wiring systems. *That one conductor is serving
as the neutral for both the distribution system and the premises
wiring systems served by the transformers that are connected in
succession to each phase of the distribution. *That uninsulated
conductor is grounded at intervals along it's route from the
substation transformer were the distribution current originated. *In
normal operation it carries comparatively little current because of
the cancellation that occurs in the common connections. *The only
current flowing on the neutral is the total difference between the
current flowing on the three phases. *Not the sum mind you just the
difference. *So if phase A is carrying one hundred, phase B one
hundred five, and phase C one hundred three amperes the maximum
current flowing in the neutral conductor at any given instant is five
amperes. *The actual purpose that the neutral current serves is to
provide a larger number of common neutral connections in which the
currents from the three phases can cancel each other out. *In any
portion of a three phase distribution system were all three phases are
not present the neutral will carry the same current as the highest
current on the one or two phases that are still present. *It is only
in the three phase portion of the network that the current will cancel
out to a very small value. *Once that portion of the system ties back
into the three phase portion of the network then the current averaged
from all such single phased stubs will again cancel out and the
neutral current will again be a rather small value.

--
Tom Horne- Hide quoted text -

- Show quoted text -

I'm with you on the essence of what you are saying regarding
how the power is distributed. Where
I still have questions is back to the original observation. Out
on country roads, you have 3 high voltage wires, one for
each phase. Then you'll have a group of houses. There
is a transformer for those houses and it's connected to
one phase. Since there are only 3 primary high voltage
wires, are you saying the other side of the transformer is
connected to the same neutral as the 240V services of
the houses? I can see that working, as then you have
multiple connections to earth ground for return on the
primary side. But then there is
also clearly substantial current flowing through earth
ground back to the substation or more likely I guess
to other earth ground points with other nearby pole
transformers that are on different phases.

If it's not done that way, then I don't understand the
return path from that pole transformer. All I see are
the 3 high voltage wires and then below it the 3
240V service wires, 2 hots, one neutral,
going down the road. In other
words, there is no neutral return path that I can
see other than the 240V, secondary one. So, is it shared?
I think that is what Bud said he thought might be
going on too. And that seems to be the essence
of the OP's question that has him stumped.

On 2/24/2012 9:45 AM, Evan wrote:
On Feb 24, 10:14 am, wrote:
I just noticed that all the residential transformers on the poles on
my street only have one wire feeding them. There are three wires on
top of the pole.

One wire in, and three wires out to the triplex feeding my house.
There are no other visible connections on the transformer.

Heck, the next street over only has ONE wire at the top of the pole...

I thought the three wires on the pole corresponded to each leg on my
breaker panel, and a ground wire.

How is the transformer creating two 110V legs and a ground from one
feed wire? This just goes against everything I learned in school about
electricity.

Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

~~ Evan

Totally irrelevant to what dennis asked.

In the urban area here the primary return is by the continuous secondary
neutral, which attaches to the primary neutral at the feed point. It is
multi-grounded, but the wire is lower resistance than the earth (or at
least lower resistance than the earth connection). In rural areas I
don't remember anywhere there wasn't another wire on the pole in
addition to 1 or 3 distribution wires. Transmission wires don't
necessarily have a neutral because it can be created at a substation.
There may be solely earth return somewhere in the state, but I don't
remember seeing it.

--
bud--

On 2/25/2012 1:56 AM, The Daring Dufas wrote:
On 2/24/2012 8:14 PM, Pete C. wrote:

The Daring Dufas wrote:

On 2/24/2012 6:52 PM, gregz wrote:
"Pete wrote:
Metspitzer wrote:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST),
wrote:

On Feb 24, 10:45 am, wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

http://imgur.com/gFrGBr

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

I believe 7,200V is about the lowest you will find anywhere and
most are
13,200V or more.

I was lying in bed one day watching guys adding a new transformer
outside
the window. When trying to clip the wire onto the hv wire I saw a
pretty
good arc. Probably at least 3 inches. A transformer feeding the
house burnt
out, so they replaced that, and added another transformer in
addition to
original. Result our house had less voltage fluctuations. When young, I
used to use the shortwave radio, and ever so often, maybe twice a ay, a
horrendous arching- buzzing sound would build up and quickly stop.
Lasting
3-4 seconds. I never found the source of that. Didn't sound like
anything
that would be consumer generated.

Greg

It could have been a static discharge from your antenna if you had an
external antenna. Or it could have been a static electricity discharge
from another source, even atmospheric. Another source may have been
power company or an industrial site switching high voltage power at
certain times every day. I can remember listening to distant stations
on an AM radio in different bands and hearing a "zip..zip..zip" sound
at regular intervals.

TDD

HID Street light ballast igniters are known to produce a lot of RFI when
they come on at night, and if they have a bad lamp attached they cycle
endlessly producing interference. With the switch to LED street lights
and even parking lot lights that problem should gradually become a thing
of the past.

A electrical engineer friend of mine was once the head of a power
company communications division and he told me that many complaints
of radio interference his department investigated turned out to be
caused by defective doorbell transformers.

TDD


Sounded pretty crazy the first time I saw you post it.

Jeff Wisnia came up with an FCC interference handbook
http://tinyurl.com/63ob78
or
http://transition.fcc.gov/ftp/Bureau...ceHandbook.pdf

that gives details. Some doorbell transformers have a thermal protector
on the primary that opens (and closes) if the transformer overheats. (It
may be part of the limitation on current/power for a class 2
transformer.) It can wind up cycling maybe 7 times a second. My guess is
that doorbell transformers have not been made that way for quite a while.

--
bud--

On 2/24/2012 6:25 PM, HeyBub wrote:
wrote:

I think the return path for the other side of the primary
transformer is the earth. Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. I see what the OP and you
are talking about all over here in rural NJ. You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. I believe
the other side is connected to earth ground. That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

pic
http://thereifixedit.files.wordpress...t-to-earth.jpg



Ahhhh-haaaaa!

So that's how they ground the Space Station and other satellites!

On 2/25/2012 9:44 AM, wrote:
On Feb 24, 9:24 pm, Tom wrote:
On Feb 24, 8:52 pm, wrote:





On Fri, 24 Feb 2012 17:36:07 -0800 (PST), Tom Horne

wrote:
I think the return path for the other side of the primary
transformer is the earth. Earth is used as a return in
many distribution systems and while it saves money,
it leads to some problems. I see what the OP and you
are talking about all over here in rural NJ. You have 3
wires on top of the poles, which are the 3 phases.
If you look at where you have houses, a single wire
leads from one of those to the transformer. I believe
the other side is connected to earth ground. That
arragement then serves a small group of houses. With a
larger commercial/industiral user you see 3 transfomers,
one connected to each of the 3 phases.

In most of North America we use a Multi Grounded Neutral (MGM). That
means that there is a neutral conductor that goes back to the source
transformer's neutral point that is grounded at multiple points along
it's route. Yes there are exceptions but they are not in common use.
The reason that system is used is because it saves a lot of money
while still providing reliable service. The neutral in most utility
distribution systems is common to both windings of the transformer.
It connects to the uninsulated stud on the transformers case which is
internally bonded to one end of the primary winding and the center of
the secondary winding. There is only one insulated connection to the
primary winding and that is the other end from the neutral
connection. The grounded stud on the case is connected to the neutral
and to ground. Since the current will flow in all pathways available
to it in proportion to the total impedance of the pathway some current
will flow via the earth on the order of a few amperes per grounding
electrode.

Here is where it gets confusing. The reason that all of those
currents do not add up to some phenomenal current flow through the
earth is that the flows from the three phases cancel each other out in
all of the common connections to the degree that the current being
drawn from the system is equal. If you ran impossibly long leads from
a three phase power analyzer what you would see across any three
consecutive transformers grounds would approach zero current. Since
no system is perfectly balanced across all three phases the current in
the neutral and the earth is never zero but if you check the current
flow in the source transformers neutral and it's grounding electrode
conductor back at the power substation you would find that it is
rather low.

So while it is true that in an MGM distribution system some of the
current is flowing through the earth the actual amperage doing that is

Wouldn't the situation where the primary is feed by a single conductor
have the same amperage returning through the earth as supplied by the
phase conductor? I wouldn't consider that "rather small"

rather small. The earth carrying current seldom causes any problems
in systems that are maintained to the National Electrical Safety Code
standard. The biggest exception is in the animal husbandry industries
were the four footed critters that spend much of their day standing or
lying in their own rather conductive waste do often suffer ill effects
from event the small stray currents that are flowing across the
ground. When some defect in the distribution neutral raises that
current a little higher the animals suffer greatly and even die from
the effects. In dairy cows for instance it will cause a drastic
reduction in production and radical changes in the cows behavior and
temperament because the animals are in nearly constant pain.
Utilities in areas with large dairying industry. Have developed
transformers with high impedance connections to ground in order to
limit the stray current to levels that are imperceptible to the
livestock. One of the utilities in Wisconsin painted these special
transformers to look like the coloration of the locally dominant type
of dairy cow.

I hope that is helpful.

No. Because the primary is supplied from two conductors. In a Multi
Grounded Neutral (MGM) distribution system there is a continuous
neutral conductor. It is the same neutral conductor that is part of
the low lines; that is the lines below the transformer; that supply
the individual premise wiring systems. That one conductor is serving
as the neutral for both the distribution system and the premises
wiring systems served by the transformers that are connected in
succession to each phase of the distribution. That uninsulated
conductor is grounded at intervals along it's route from the
substation transformer were the distribution current originated. In
normal operation it carries comparatively little current because of
the cancellation that occurs in the common connections. The only
current flowing on the neutral is the total difference between the
current flowing on the three phases. Not the sum mind you just the
difference. So if phase A is carrying one hundred, phase B one
hundred five, and phase C one hundred three amperes the maximum
current flowing in the neutral conductor at any given instant is five
amperes. The actual purpose that the neutral current serves is to
provide a larger number of common neutral connections in which the
currents from the three phases can cancel each other out. In any
portion of a three phase distribution system were all three phases are
not present the neutral will carry the same current as the highest
current on the one or two phases that are still present. It is only
in the three phase portion of the network that the current will cancel
out to a very small value. Once that portion of the system ties back
into the three phase portion of the network then the current averaged
from all such single phased stubs will again cancel out and the
neutral current will again be a rather small value.

--
Tom Horne- Hide quoted text -

- Show quoted text -

I'm with you on the essence of what you are saying regarding
how the power is distributed. Where
I still have questions is back to the original observation. Out
on country roads, you have 3 high voltage wires, one for
each phase. Then you'll have a group of houses. There
is a transformer for those houses and it's connected to
one phase. Since there are only 3 primary high voltage
wires, are you saying the other side of the transformer is
connected to the same neutral as the 240V services of
the houses? I can see that working, as then you have
multiple connections to earth ground for return on the
primary side. But then there is
also clearly substantial current flowing through earth
ground back to the substation or more likely I guess
to other earth ground points with other nearby pole
transformers that are on different phases.


I have been on a lot of country roads and have never seen what you
described. Typically there are the Y derived phase conductors on a
crossarm or bracket with three insulators and an uninsulated neutral
below. As density gets lower they will only carry one of the primary
conductors and the neutral.






If it's not done that way, then I don't understand the
return path from that pole transformer. All I see are
the 3 high voltage wires and then below it the 3
240V service wires, 2 hots, one neutral,
going down the road. In other
words, there is no neutral return path that I can
see other than the 240V, secondary one. So, is it shared?
I think that is what Bud said he thought might be
going on too. And that seems to be the essence
of the OP's question that has him stumped.

On 2/24/2012 3:12 PM, Pete C. wrote:

Metspitzer wrote:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST), wrote:

On Feb 24, 10:45 am, wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

http://imgur.com/gFrGB

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

I believe 7,200V is about the lowest you will find anywhere and most are
13,200V or more.

They are both.

The pretty much standard system is a Y derived HV primary ~ 12kv phase
to phase or ~ 7.2kv phase to neutral.

bud-- wrote:
On 2/25/2012 1:56 AM, The Daring Dufas wrote:
On 2/24/2012 8:14 PM, Pete C. wrote:

The Daring Dufas wrote:

On 2/24/2012 6:52 PM, gregz wrote:
"Pete wrote:
Metspitzer wrote:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST),
wrote:

On Feb 24, 10:45 am, wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.

http://imgur.com/gFrGBr

I used 8000 for the primary from someone's earlier post. No clue what
it really is.

I believe 7,200V is about the lowest you will find anywhere and
most are
13,200V or more.

I was lying in bed one day watching guys adding a new transformer
outside
the window. When trying to clip the wire onto the hv wire I saw a
pretty
good arc. Probably at least 3 inches. A transformer feeding the
house burnt
out, so they replaced that, and added another transformer in
addition to
original. Result our house had less voltage fluctuations. When young, I
used to use the shortwave radio, and ever so often, maybe twice a ay, a
horrendous arching- buzzing sound would build up and quickly stop.
Lasting
3-4 seconds. I never found the source of that. Didn't sound like
anything
that would be consumer generated.

Greg

It could have been a static discharge from your antenna if you had an
external antenna. Or it could have been a static electricity discharge
from another source, even atmospheric. Another source may have been
power company or an industrial site switching high voltage power at
certain times every day. I can remember listening to distant stations
on an AM radio in different bands and hearing a "zip..zip..zip" sound
at regular intervals.

TDD

HID Street light ballast igniters are known to produce a lot of RFI when
they come on at night, and if they have a bad lamp attached they cycle
endlessly producing interference. With the switch to LED street lights
and even parking lot lights that problem should gradually become a thing
of the past.

A electrical engineer friend of mine was once the head of a power
company communications division and he told me that many complaints
of radio interference his department investigated turned out to be
caused by defective doorbell transformers.

TDD


Sounded pretty crazy the first time I saw you post it.

Jeff Wisnia came up with an FCC interference handbook
http://tinyurl.com/63ob78
or
http://transition.fcc.gov/ftp/Bureau...ceHandbook.pdf

that gives details. Some doorbell transformers have a thermal protector
on the primary that opens (and closes) if the transformer overheats. (It
may be part of the limitation on current/power for a class 2
transformer.) It can wind up cycling maybe 7 times a second. My guess is
that doorbell transformers have not been made that way for quite a while.


I had two houses but never heard of that. Perhaps I did and forgot. Years
ago our ham club had an interference expert from PG&E, come in to our
meeting. The way he tracked down that type of interference was use am
radios. You start at the broadcast band then work your way up in frequency,
narrowing down the location. Like, am broadcast, cb, aircraft band, etc.

The transformers I see know have a thermal break, for good.

Greg

On 02/25/2012 11:30 AM, George wrote:

[snip]

I have been on a lot of country roads and have never seen what you
described. Typically there are the Y derived phase conductors on a
crossarm or bracket with three insulators and an uninsulated neutral
below. As density gets lower they will only carry one of the primary
conductors and the neutral.

The one here appears to have the neutral on top. See the picture at
http://notstupid.us/pix/IMG_3427.JPG

[snip]

--
Mark Lloyd
http://notstupid.us

"A fanatic is one who can't change his mind and won't change the
subject." -- Winston Churchill

Metspitzer wrote in
:

On Fri, 24 Feb 2012 08:30:26 -0800 (PST), wrote:

On Feb 24, 10:45*am, Evan wrote:
Read up more on transformers...

Residential power is typically single phase (although there are
some exceptions to this) with a center tapped secondary winding
on the transformer...

The thing is, everything I know about electricity says that you need
TWO wires to make a complete circuit. AC or DC, doesn't matter.

Most streets have two overhead wires, with two wires going to the
transformer.


http://imgur.com/gFrGB

I used 8000 for the primary from someone's earlier post. No clue what
it really is.


talking to the utility guy replacing the power transformer on the
ground outside my apartment(after it blew),it was fed by 7200 volts,coming
from a nearby pole.

--
Jim Yanik
jyanik
at
localnet
dot com