- Location
- Wisconsin
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- PE (Retired) - Power Systems
Not working for a POCO, I would agree.
system grounding
- Thread starter robeward
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Not working for a POCO, I would agree.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Usually they will read, "4160gy/2400 or "4160grndy/2400" if it's a single bushing unit. Obviously you can use a two bushing unit connected L-N, but not a single bushing connected L-L (where L designates an ungrounded conductor). I would think these days a two bushing 2400 transformer is mostly extinct except for old units, as utilities have converted these systems to 4160y
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
That would be gy or grndy as in grounded wye, I assume.
The NEC designation 4160Y/2400 does not tell us one way or the other about whether it is a grounded system.
The NEC designation 4160Y/2400 does not tell us one way or the other about whether it is a grounded system.
And your output will be 2400V. Not 4160V, right?
IEEE Std. C57.12.00 (ftp://mail.sptc.com.sa/Specs&Standard/IEEEANSI/2010/IEEE Std C57.12.00-2010.pdf)
See Tables 8 and 9.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
That is good info, thanks.
I fully understand and agree with the "Remove the bonding strap connected to PRI X2 in the step up transformer".
However I do not understand: "Connect it to SEC H2 along with the secondary grounded conductor (currently depicted as connected to enclosure on right side)". I would not connect that PRI X2 to anything. Maybe you might be able to explain so I can understand.
I did not know he was using an oil-immersed transformer [with internal factory bondings] at the time I wrote that. Yea, de signs where dere but dey just flew right over me head. I was thinking dry transformer. Alas!
Remove the bonding strap completely and ignore all else in my earlier post.
I am still getting through all the responses. Sorry the email notifications quite coming in.
Yes most commonly used for step down. Can you explain how you came up with 138v please?
Exactly right. Long cable run. When we buy them we tell cooper when we are going to use it for step up operation but the strap seems to be installed regardless.
Yes most commonly used for step down. Can you explain how you came up with 138v please?
Exactly right. Long cable run. When we buy them we tell cooper when we are going to use it for step up operation but the strap seems to be installed regardless.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
The trick is actually easier than it should be. You represent each voltage and phase by a vector that has length equal to the voltage and a direction equal to the phase angle.
To add two voltages (of arbitrary phase) together, you simply add the vectors (connect them head to tail).
It is rendered very easy since your transformer diagram already puts the coils in the appropriate directions.
Draw your symmetric 'wye' and call the length of each leg 277 'units'. The angle of each leg of the wye is the phase angle for that phase. The length between any two 'tips' of the wye will be 480 units, and its angle will be the phase angle of the 480V connection. Draw this 480V line, and find its midpoint. Measure the distance from the neutral of the wye to the midpoint of the 480V leg.
-Jon
seem to be a lot of discussion over the designation. couple things. you can't just rely on how many HV bushings you see for determining voltage. if you go back and look of the picture of the xfmr there are actually two HV bushings but they are internally tied. we use one for source and usually install an elbow MOV on the other.
i have an attachment provided by cooper that explains the designation. essentially the designation determines how the xfmr is built. either one coil/mid tap or two coils connected. internally grounded or not. some can be used in wye configurations and some can't. it references an ANSI standard that governs this but doesn't actually give the name. the file is too big. once i figure out a way to make it available i will post it.
i have an attachment provided by cooper that explains the designation. essentially the designation determines how the xfmr is built. either one coil/mid tap or two coils connected. internally grounded or not. some can be used in wye configurations and some can't. it references an ANSI standard that governs this but doesn't actually give the name. the file is too big. once i figure out a way to make it available i will post it.
Dag. I was stuck in single phase mode. Forgot to take into account angles from the source. let me ponder on this.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Good article, thanks. Similar to the one Smart$ posted but this one is more specific for single phase and gives a little more detail with examples.
Yes the loop feed bushing can throw you off, it did the same to me. I have a step up step down setup serving my house, and I was also planning on using the loop feed bushing for an arrestor elbow.
Out of curiosity, did they supply a different transformer for the step up an down or are they both the same?
Yes technically there is a difference but without the order form showing which one is which, I don't think you could tell the difference just by looking at them. Physically there is not difference and I honestly don't know what would make them different. The impedance numbers are different but I am not sure it is enough to say they build them in a different way. Maybe someone up here could shed some light.
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