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Home > Archive > Electrical Engineering > May 2007 > 3 phase
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| rywells@gmail.com 2007-04-30, 1:25 pm |
| I was told that a three phase Y connection has three hot legs, one
ground and a neutral. Is this true?
thanks for your help,
Ryan
| |
| SparkyGuy 2007-04-30, 1:25 pm |
| > I was told that a three phase Y connection has three hot legs, one
> ground and a neutral. Is this true?
>
> thanks for your help,
> Ryan
The "Y" configuration: each leg of the "Y" is one phase. The phases of the
voltages are, nominally, 120 degrees in relation to each other. They are
connected together at the common point which is the neutral. A proper ground
conductor should always be included whenever power is conveyed over wires.
| |
| Beachcomber 2007-04-30, 5:25 pm |
| On Mon, 30 Apr 2007 09:25:29 -0700, SparkyGuy <SparkyGuy@mumcrank.ck>
wrote:
>
>The "Y" configuration: each leg of the "Y" is one phase. The phases of the
>voltages are, nominally, 120 degrees in relation to each other. They are
>connected together at the common point which is the neutral. A proper ground
>conductor should always be included whenever power is conveyed over wires.
>
....unless it is high voltage transmission, in which case it is more
economical to transmit the power with 3 wires instead of 4 .
| |
| phil-news-nospam@ipal.net 2007-05-02, 1:27 pm |
| On Mon, 30 Apr 2007 20:11:30 GMT Beachcomber <invalid@notreal.none> wrote:
| On Mon, 30 Apr 2007 09:25:29 -0700, SparkyGuy <SparkyGuy@mumcrank.ck>
| wrote:
|
|>> I was told that a three phase Y connection has three hot legs, one
|>> ground and a neutral. Is this true?
|>>
|>> thanks for your help,
|>> Ryan
|>
|>The "Y" configuration: each leg of the "Y" is one phase. The phases of the
|>voltages are, nominally, 120 degrees in relation to each other. They are
|>connected together at the common point which is the neutral. A proper ground
|>conductor should always be included whenever power is conveyed over wires.
|>
|
| ...unless it is high voltage transmission, in which case it is more
| economical to transmit the power with 3 wires instead of 4 .
Given that with the high diversity of the very large number of loads
a transmission line would serve, the power would almost entirely be
transmitted on 3 wires even if a 4th was present (e.g. if Y instead
of D). Another question is whether the source transformer for such
a transmission line is wired Y or wired D. At this scale, they sure
would be expected to make this choice correctly.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-05-02-1039@ipal.net |
|------------------------------------/-------------------------------------|
| |
| Don Kelly 2007-05-02, 9:25 pm |
|
<phil-news-nospam@ipal.net> wrote in message
news:f1abj90fo0@news4.newsguy.com...
> On Mon, 30 Apr 2007 20:11:30 GMT Beachcomber <invalid@notreal.none> wrote:
> | On Mon, 30 Apr 2007 09:25:29 -0700, SparkyGuy <SparkyGuy@mumcrank.ck>
> | wrote:
> |
> |>> I was told that a three phase Y connection has three hot legs, one
> |>> ground and a neutral. Is this true?
> |>>
> |>> thanks for your help,
> |>> Ryan
> |>
> |>The "Y" configuration: each leg of the "Y" is one phase. The phases of
> the
> |>voltages are, nominally, 120 degrees in relation to each other. They are
> |>connected together at the common point which is the neutral. A proper
> ground
> |>conductor should always be included whenever power is conveyed over
> wires.
> |>
> |
> | ...unless it is high voltage transmission, in which case it is more
> | economical to transmit the power with 3 wires instead of 4 .
>
> Given that with the high diversity of the very large number of loads
> a transmission line would serve, the power would almost entirely be
> transmitted on 3 wires even if a 4th was present (e.g. if Y instead
> of D). Another question is whether the source transformer for such
> a transmission line is wired Y or wired D. At this scale, they sure
> would be expected to make this choice correctly.
>
> --
> |---------------------------------------/----------------------------------|
> | Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below
> |
> | first name lower case at ipal.net / spamtrap-2007-05-02-1039@ipal.net
> |
> |------------------------------------/-------------------------------------|
High voltage lines are supplied from a Y source (eg transformer LV most
often delta, HV Y).
There may or may not be a neutral carried along but usually a multigrounded
neutral is carried overhead, serving for lightning shielding.
Delta supplied transmission systems pretty well disappeared about 75 years
ago. Part of the problem is that with an ungrounded system, atmospheric
conditions mayuse the line to ground voltage to float up to a point where a
flashover to ground occurs. There can be enough capacitive follow through
current to cause severe arcing and damage but such currents are hard to
detect. Rather than use some grounding technique such as zig-zag
transformers, it is simpler to go with a Y system. Ground fault detection is
simpler. There are also economic advantages-particularly in HV transformers.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
| |
| phil-news-nospam@ipal.net 2007-05-06, 3:25 am |
| On Thu, 03 May 2007 02:08:37 GMT Don Kelly <dhky@shaw.ca> wrote:
| High voltage lines are supplied from a Y source (eg transformer LV most
| often delta, HV Y).
| There may or may not be a neutral carried along but usually a multigrounded
| neutral is carried overhead, serving for lightning shielding.
| Delta supplied transmission systems pretty well disappeared about 75 years
| ago. Part of the problem is that with an ungrounded system, atmospheric
| conditions mayuse the line to ground voltage to float up to a point where a
| flashover to ground occurs. There can be enough capacitive follow through
| current to cause severe arcing and damage but such currents are hard to
| detect. Rather than use some grounding technique such as zig-zag
| transformers, it is simpler to go with a Y system. Ground fault detection is
| simpler. There are also economic advantages-particularly in HV transformers.
So why not corner grounded?
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-05-05-2350@ipal.net |
|------------------------------------/-------------------------------------|
| |
| Don Kelly 2007-05-08, 3:25 am |
| Higher insulation to ground for the ungrounded legs and more expensive
transformers. (going LV delta to HV Y has $ advantages). Higher ground
currents in normal operation and the most common fault becomes line to line
rather than line to ground.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
<phil-news-nospam@ipal.net> wrote in message
news:f1jmr001jt6@news4.newsguy.com...
> On Thu, 03 May 2007 02:08:37 GMT Don Kelly <dhky@shaw.ca> wrote:
>
> | High voltage lines are supplied from a Y source (eg transformer LV most
> | often delta, HV Y).
> | There may or may not be a neutral carried along but usually a
> multigrounded
> | neutral is carried overhead, serving for lightning shielding.
> | Delta supplied transmission systems pretty well disappeared about 75
> years
> | ago. Part of the problem is that with an ungrounded system, atmospheric
> | conditions mayuse the line to ground voltage to float up to a point
> where a
> | flashover to ground occurs. There can be enough capacitive follow
> through
> | current to cause severe arcing and damage but such currents are hard to
> | detect. Rather than use some grounding technique such as zig-zag
> | transformers, it is simpler to go with a Y system. Ground fault
> detection is
> | simpler. There are also economic advantages-particularly in HV
> transformers.
>
> So why not corner grounded?
>
> --
> |---------------------------------------/----------------------------------|
> | Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below
> |
> | first name lower case at ipal.net / spamtrap-2007-05-05-2350@ipal.net
> |
> |------------------------------------/-------------------------------------|
| |
| gfretwell@aol.com 2007-05-08, 1:25 pm |
| On Tue, 08 May 2007 05:27:36 GMT, "Don Kelly" <dhky@shaw.ca> wrote:
>Higher insulation to ground for the ungrounded legs and more expensive
>transformers. (going LV delta to HV Y has $ advantages). Higher ground
>currents in normal operation and the most common fault becomes line to line
>rather than line to ground.
>
>--
>
>Don Kelly dhky@shawcross.ca
>remove the X to answer
>----------------------------
><phil-news-nospam@ipal.net> wrote in message
[color=darkred]
Corner grounded secondaries are very popular where you have motor only
loads like a sewer pump station. It allows the installer to use 2 pole
equipment for 3 phase loads. The problem is, you don't get L/N voltage
for 120v loads. As long as the station is designed with this in mind
there is really no problem there. You just use all 240v equipment.
There is also a confusion factor for the unqualified but unqualified
people should not be there anyway.
| |
| phil-news-nospam@ipal.net 2007-05-12, 9:25 pm |
| On Tue, 08 May 2007 05:27:36 GMT Don Kelly <dhky@shaw.ca> wrote:
| Higher insulation to ground for the ungrounded legs and more expensive
| transformers. (going LV delta to HV Y has $ advantages). Higher ground
| currents in normal operation and the most common fault becomes line to line
| rather than line to ground.
OK, so what does the other end of the transmission line have? Also Y on
the HV side and D on the LV side? Or is it delta loaded? I would think
at least some transmission lines have to be designed for possible reverse
usage, and I would think switching transformers to switch direction would
be a pain and a lot of $$$.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-05-12-2051@ipal.net |
|------------------------------------/-------------------------------------|
| |
| phil-news-nospam@ipal.net 2007-05-12, 9:25 pm |
| On Tue, 08 May 2007 11:35:54 -0400 gfretwell@aol.com wrote:
| On Tue, 08 May 2007 05:27:36 GMT, "Don Kelly" <dhky@shaw.ca> wrote:
|
|>Higher insulation to ground for the ungrounded legs and more expensive
|>transformers. (going LV delta to HV Y has $ advantages). Higher ground
|>currents in normal operation and the most common fault becomes line to line
|>rather than line to ground.
|>
|>--
|>
|>Don Kelly dhky@shawcross.ca
|>remove the X to answer
|>----------------------------
|><phil-news-nospam@ipal.net> wrote in message
|
|>>
|>> So why not corner grounded?
|
|
| Corner grounded secondaries are very popular where you have motor only
| loads like a sewer pump station. It allows the installer to use 2 pole
| equipment for 3 phase loads. The problem is, you don't get L/N voltage
| for 120v loads. As long as the station is designed with this in mind
| there is really no problem there. You just use all 240v equipment.
| There is also a confusion factor for the unqualified but unqualified
| people should not be there anyway.
There are corner grounded 120V systems. They just happen to typically be
(or once were) on railroad cars. But if you needed 120V and needed to do
three phase in 2-pole circuits, and didn't mind to heavy up the neutral
for the single phase loads, why not do a CG120 system?
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-05-12-2053@ipal.net |
|------------------------------------/-------------------------------------|
|
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