Wye to wye questions

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electrofelon said:
Right, they may just be using that because it's super common, doesn't mean its a grounded system with a neutral.....but there appears to be a ground wire (SSBJ) going to the utility which implies it is, 250.86(B) . You need clarification from the utility what kind of system it is, and the designer about the grounding connections. Often not all grounding connections are shown on drawings.
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Will ask the designer and let you know but 250.186(A) and 250.186(B) are about AC grounded system just one is neutral brought and other neutral is not brought. Also I dont see Article 250.86(B)? You mean 250.186(B)?
 
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hhsting said:
Will ask the designer and let you know but 250.186(A) and 250.186(B) are about AC grounded system just one is neutral brought and other neutral is not brought. Also I dont see Article 250.86(B)? You mean 250.186(B)?
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Yes meant 186. I believe what they intend for the case where there is no neutral provided, is you run a SSBJ and the POCO connects it to their neutral/grounded conductor.
 
electrofelon said:
Yes meant 186. I believe what they intend for the case where there is no neutral provided, is you run a SSBJ and the POCO connects it to their neutral/grounded conductor.
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That might explain SSBJ but at each equipment 13.2kV side each ground bar has SSBJ connection and GEC to electrodes why is that done? I.e. SSBJ is tide to GEC at each equipment gnd bar.

Also neutral is brought from utility if its needed. Inverter needs neutral and so does heaters and receptacle but all that is on 600VaC side wye. Heaters and receptacle are on secondary of 5kVA xfmr side and primary has no neutral brought just two phase leg and EGC. Xo and Ho of 2000kVA xfmr 600V to 13.2kV wye to wye are typically bonded so how does that work if their is no neutral brought on Ho 13.2kV side but MV80 phase cable has concentric neutral? If X0 and H0 are not bonded then it is ok neutral need to be continous back to utility but terminate windings of 600VAC side? Then again if Xo and Ho are not bonded then why need for wye13.2kV side?
 
hhsting said:
The inverter that is being used is wye not delta so that side has to be wye.
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Yes, we know; you are creating a neutral for it at the transformer. Separately derived. That has nothing to do with whether there is a neutral or not from the service to the other side of the transformer. Even if there is they won't be bonded to each other.
 
ggunn said:
Yes, we know; you are creating a neutral for it at the transformer. Separately derived. That has nothing to do with whether there is a neutral or not from the service to the other side of the transformer. Even if there is they won't be bonded to each other.
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The inverter instruction post #18 shows otherwise wye wey xfmr. Wye to wye xfmr X0 and H0 terminal wont be internally comnected?
Also, how can there be neutral at H0 if utility wont bring neutral wye to wye xfmr?
 
hhsting said:
The inverter instruction post #18 shows otherwise wye wey xfmr. Wye to wye xfmr X0 and H0 terminal wont be internally comnected?
Also, how can there be neutral at H0 if utility wont bring neutral wye to wye xfmr?
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X0 and H0 will not be internally connected. Look at the drawing; it does not show a connection between the center points of the wyes.

As to there not being a neutral from the service to the primary of the transformer, that's how it should be. There is no difference on the secondary side whether it's a wye - wye with no neutral or a delta on the primary side. I was just questioning why it's a wye - wye transformer because most I have seen used this way have been wye - delta, with the caveat that I don't know nuthin' 'bout no MV PV interconnections.
 
ggunn said:
X0 and H0 will not be internally connected. Look at the drawing; it does not show a connection between the center points of the wyes.

As to there not being a neutral from the service to the primary of the transformer, that's how it should be. There is no difference on the secondary side whether it's a wye - wye with no neutral or a delta on the primary side. I was just questioning why it's a wye - wye transformer because most I have seen used this way have been wye - delta, with the caveat that I don't know nuthin' 'bout no MV PV interconnections.
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I am talking about post #18 inverter instruction attachment which shows wye to wye transformer and shows yellow dotted line centerof wye and blue dotted line another center of wye going to ground symbol. See note as well which says x0 and h0 maybe connected.
 
hhsting said:
I am talking about post #18 inverter instruction attachment which shows wye to wye transformer and shows yellow dotted line centerof wye and blue dotted line another center of wye going to ground symbol. See note as well which says x0 and h0 maybe connected.
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That is optional. Note it says "per utility requirements". That is common utility practice (for utility owned transformers). It's also how it would be for an MGN setup. Primary neutral would not be grounded for a single point grounded neutral.

If that utility system is grounded, I'm sure the utility would give you a neutral if you asked.
 
electrofelon said:
That is optional. Note it says "per utility requirements". That is common utility practice (for utility owned transformers). It's also how it would be for an MGN setup. Primary neutral would not be grounded for a single point grounded neutral.

If that utility system is grounded, I'm sure the utility would give you a neutral if you asked.
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I mean they provide cables with concentric neutral I guess thats not neutral.

Series of questions need to be asked i guess to designer:

First question is incoming utility 13.2kV conductors are they grounded AC system or ungrounded AC system?

Second question is if ungrounded then its permitted NEC 2014 Article 250.20(C) nothing else to be done and if grounded then question to ask 250.186(A) or (B) neutral brought or not and is it 250.184(B) or (C) single point neutral or multiground neutral?

yes or no?
 
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ggunn said:
X0 and H0 will not be internally connected. Look at the drawing; it does not show a connection between the center points of the wyes.

As to there not being a neutral from the service to the primary of the transformer, that's how it should be. There is no difference on the secondary side whether it's a wye - wye with no neutral or a delta on the primary side. I was just questioning why it's a wye - wye transformer because most I have seen used this way have been wye - delta, with the caveat that I don't know nuthin' 'bout no MV PV interconnections.
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I looked at the drawing and wondered why it wasn’t bonded internally.
I agree, according to the drawing it isn’t.
I would rather see the dataplate on the XF to be sure.

for the record, I know ground faults are transferred with Wye Wye, but the only place we will put a delta primary is after a three phase recloser. We don’t need backfeed if one phase drops on the ground.

then there’s ferroresonance...
 
Hv&Lv said:
I looked at the drawing and wondered why it wasn’t bonded internally.
I agree, according to the drawing it isn’t.
I would rather see the dataplate on the XF to be sure.

for the record, I know ground faults are transferred with Wye Wye, but the only place we will put a delta primary is after a three phase recloser. We don’t need backfeed if one phase drops on the ground.

then there’s ferroresonance...
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The original drawing i have has ground symbol on each wye windings. So 600 vac wye has gnd symbol and 13.2kv wye winding has gnd symbol.
 
hhsting said:
I mean they provide cables with concentric neutral I guess thats not neutral.

Series of questions need to be asked i guess to designer:

First question is incoming utility 13.2kV conductors are they grounded AC system or ungrounded AC system?

Second question is if ungrounded then its permitted NEC 2014 Article 250.20(C) nothing else to be done and if grounded then question to ask 250.186(A) or (B) neutral brought or not and is it 250.184(B) or (C) single point neutral or multiground neutral?

yes or no?
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Can anyone here help above questions?
 
ggunn said:
X0 and H0 will not be internally connected. Look at the drawing; it does not show a connection between the center points of the wyes.
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I respectfully disagree.
The drawing isn’t accurate.
 
All the other stuff is their all that was not their were these ground symbols of wye. Rest of the other stuff is their. Fed from 15kv 3 - MV 90 cables with concentric neutral. Each equipment have gnd bar with GEC going to electrode. 600v swbd having gnd to neutral with GEC to electrodes. I dont see what is it now that you see that you are getting somewhere???i
 
hhsting said:
All the other stuff is their all that was not their were these ground symbols of wye. Rest of the other stuff is their. Fed from 15kv 3 - MV 90 cables with concentric neutral. Each equipment have gnd bar with GEC going to electrode. 600v swbd having gnd to neutral with GEC to electrodes. I dont see what is it now that you see that you are getting somewhere???i
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Forget the padmount.
think of it like an overhead bank.
the concentric neutral cable IS the neutral wire on the 13.2 side.
it is bonded to the secondary side like I stated in post #2.
that means there is a wire from the neutral in your very last panel that is the same as the wire coming into the XF.
the ground wire from your very last panel is also bonded to this same wire, hopefully at the main and not everywhere else.
 
Hv&Lv said:
Forget the padmount.
think of it like an overhead bank.
the concentric neutral cable IS the neutral wire on the 13.2 side.
it is bonded to the secondary side like I stated in post #2.
that means there is a wire from the neutral in your very last panel that is the same as the wire coming into the XF.
the ground wire from your very last panel is also bonded to this same wire, hopefully at the main and not everywhere else.
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The ground to neutral is bonded at the 600VAC switchboard only not at the 15kV main switchboard. Should neutral to ground bond exist only 15kV switchboard and not at 600V switchboard?

Also would the transformer be separately derived system if neutral is bonded to secondary side?
 
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