Wye to wye questions

[electrofelon]

The design is to supply power from your side to POCO. So POCO side is load side in your case and 600V SWbd is 'service board'.

No. Here, the direction of net energy transfer does not change those definitions and rules.

 

[Sahib]

No. Here, the direction of net energy transfer does not change those definitions and rules.

Ok. But the OP must bond the POCO neutral to the 600V SWbd ground instead of at 13.2KV SWbd to have single point grounding.

 

[electrofelon]

Ok. But the OP must bond the POCO neutral to the 600V SWbd ground instead of at 13.2KV SWbd to have single point grounding.

Please please do not confuse things, this is already confusing enough for the OP. Besides your statement doesnt make any sense. Neutral would be bonded at 13.2 KV service equipment, and separate N-G from there after to be single point.

 

[hhsting]

The design is to supply power from your side to POCO. So POCO side is load side in your case and 600V SWbd is 'service board'.

Perhaps your location in different country i.e.India it is however here we must follow code i.e. NEC 2014 at this location and according to NEC 2014 defintion of service says from utility i.e. 13.2kV swbd.

 

[hhsting]

I think I already gave some plausible justification for that N-G bond in the 600V switchboard: 1) Call it an SDS (which IMO is a silly distinction that a field installed connection doesnt make it an SDS where has factory installed does) 2) use 250.30(A)(1) exception 2. As I said, this is not fully correct and may be a stretch to some people.

Ok but have to follow NEC 2014 cant make up rules unless locally amended which is not. According to NEC 2014 defintion of separately derived i.e factory bond does not make SDS then lets say i ask engineer to go with option #2 post #81 single point. Question the concentric neutral cable also acts as shield and needs to be grounded at both ends no or can it be grounded at only one point?. How does this work with single point ground only at one point?

 

[hhsting]

Ok. But the OP must bond the POCO neutral to the 600V SWbd ground instead of at 13.2KV SWbd to have single point grounding.

I have been trying to say this and also I cannot find it in NEC 2014 that 600VAC or less than 1000V system is required to be single point only. If anyone can find it then would maybe justify 600Vac N to G.

 

[hhsting]

I think I already gave some plausible justification for that N-G bond in the 600V switchboard: 1) Call it an SDS (which IMO is a silly distinction that a field installed connection doesnt make it an SDS where has factory installed does) 2) use 250.30(A)(1) exception 2. As I said, this is not fully correct and may be a stretch to some people.

Post #66 attachment xfmr nameplate their is some sort of neutral disconnect i wonder if that can separate factory install internal x0/h0 bond?

I dont see how even with factory install internal bond x0/h0 neutrals are connected directly and xfmr is Not SDS. Based on post #2 Hv&Lv who says he/she does this everyday I have attempted to draw attached sketch 13.2kv concentric neutral is indirectly connected thru Earth ground ring electrode to 600V X0/H0 terminal exists on secondary side per post #66 xfmr nameplate and post #2. Their is no H0 connection 13.2kV primary side, concentric neutral are grounded and H1, H2, H3 are phase conductors only no neutral. Am I missing something? Hv&Lv can you help or anyone else? Unless you do #2 attachment in which case i guess one would remove conductor going from G bar 13.2kV to 600V swbd G bar?

 

[hhsting]

Post #66 attachment xfmr nameplate their is some sort of neutral disconnect i wonder if that can separate factory install internal x0/h0 bond?

I dont see how even with factory install internal bond x0/h0 neutrals are connected directly and xfmr is Not SDS. Based on post #2 Hv&Lv who says he/she does this everyday I have attempted to draw attached sketch 13.2kv concentric neutral is indirectly connected thru Earth ground ring electrode to 600V X0/H0 terminal exists on secondary side per post #66 xfmr nameplate and post #2. Their is no H0 connection 13.2kV primary side, concentric neutral are grounded and H1, H2, H3 are phase conductors only no neutral. Am I missing something? Hv&Lv can you help or anyone else? Unless you do #2 attachment in which case i guess one would remove conductor going from G bar 13.2kV to 600V swbd G bar?

No takers no one knows?

 

[electrofelon]

Their is no H0 connection 13.2kV primary side, concentric neutral are grounded and H1, H2, H3 are phase conductors only no neutral.

I am having a hard time following this. The section I quoted above, is that a question about a possibility or a statement about how it is? Can you please post a good quality image of the entire drawing from post #36? We should have had this in the OP.

I am rather lost at this point. This has been going on for so long and your responses are really hard to follow and we dont have the complete drawing. I cant remember what has or has not been established and I dont have time to go back and study all 8 pages. Submit the complete drawing and I will try once more to say if I think it is correct.

I think the main point of confusion is that happens on each end of the concentric neutral.

 

[hhsting]

I am having a hard time following this. The section I quoted above, is that a question about a possibility or a statement about how it is? Can you please post a good quality image of the entire drawing from post #36? We should have had this in the OP.

I am rather lost at this point. This has been going on for so long and your responses are really hard to follow and we dont have the complete drawing. I cant remember what has or has not been established and I dont have time to go back and study all 8 pages. Submit the complete drawing and I will try once more to say if I think it is correct.

I think the main point of confusion is that happens on each end of the concentric neutral.

Drawings are still being revised I dont have any new.

Statement is a possibility I am not sure i am asking following based on what is shown on xfmr nameplate post #66 and what post #2 says: If I am looking at 2000kVA 13.2kV xfmr primary compartment/door in field I should only see H1, H2, H3 for three phases and concentric neutrals from each phase bond to ground no other place for it and NO H0 and when I go to 600V xfmr secondary compartment/door I should only see X1, X2, X3, H0/X0 correct?

My second question if their is no H0 connection primary 13.2kV only H0/X0 secondary then attachments post #107 are they consider SDS system and wired correctly?

 

[electrofelon]

If I am looking at 2000kVA 13.2kV xfmr primary compartment/door in field I should only see H1, H2, H3 for three phases and concentric neutrals from each phase bond to ground no other place for it and NO H0 and when I go to 600V xfmr secondary compartment/door I should only see X1, X2, X3, H0/X0 correct?

My second question if their is no H0 connection primary 13.2kV only H0/X0 secondary then attachments post #107 are they consider SDS system and wired correctly?

It depends. Sometimes in the HV compartment they will have a HO bushing with a removable strap to the case, and sometimes there will not be an HO bushing, just a ground lug on the case. In LV compartment there will be an XO spade, almost always with a removable ground strap to the case.

please un-secret the entire drawing you showed a piece of in post #36.

 

[Sahib]

I have been trying to say this and also I cannot find it in NEC 2014 that 600VAC or less than 1000V system is required to be single point only. If anyone can find it then would maybe justify 600Vac N to G.

Why don't you just remove the 600v N to G connection and keep the single point grounding per your option2 drawing in consultation with the utility?

 

[Sahib]

The utility has the final say. But remember if there is no H0 bonding, you could have floating neutral problem on your side due to presence of Y-Y transformer.

 

[electrofelon]

The utility has the final say. But remember if there is no H0 bonding, you could have floating neutral problem on your side due to presence of Y-Y transformer.

Can you elaborate on this floating neutral problem?

This is one major problem with this design, is that it is based around a wye wye transformer with a specific grounding and bonding arrangement, and not being an expert at MV and wye wye transformers, I am reluctant to endorse rearranging the grounding and bonding just to meet NEC requirements.

 

[Sahib]

Can you elaborate on this floating neutral problem?

This is one major problem with this design, is that it is based around a wye wye transformer with a specific grounding and bonding arrangement, and not being an expert at MV and wye wye transformers, I am reluctant to endorse rearranging the grounding and bonding just to meet NEC requirements.

Suppose the 13.2KV side neutral point is not connected to POCO source neutral by bonding to grounded 13.2KV incoming cable shield. If there is any ground fault on 600V side, the protective device may not operate as there is only a small increase in current from inverter side and no contribution to ground fault current by POCO side as the faulted phase is pulled down to ground potential and there would be phase to ground over voltages on other two phases of 600V side.

 

[hhsting]

Attached is second page of datasheet transformer: LV compart only has H0/X0, X1, X2 and X3. HV compart only has H1, H2, H3. By the way concentric neutral should be bonded to incoming POCO concentric neutral as stated in NEC 2014 Article 250.186(A) at 13.2kV SWBD. Service point is at 13.2kV SWBD. The question is lets say I have three cable each with concentric neutral on the HV compartment I only have H1, H2, H3 and ground bar. Where does the concentric neutrals of each phase go to?

 

[ggunn]

hhsting, I humbly suggest that you hire a consultant with expertise and experience in this sort of thing rather than posing questions on the internet and trying to figure it out for yourself. MV can do a horrific amount of damage when something goes wrong.

 

[electrofelon]

The question is lets say I have three cable each with concentric neutral on the HV compartment I only have H1, H2, H3 and ground bar. Where does the concentric neutrals of each phase go to?

The the ground lug in the HV compartment. I am beginning to think that this WOULD BE an SDS, if you call that concentric conductor an EGC and not a neutral. When the definition of SDS and wye wye come together, things get kinda screwy and into semantics. So I am leaning towards: HV switchboard N-G bond, 3 phases plus EGC (concentrics used as EGC per 250.190(C)(2)) to transformer, then make N-G bond for SDS in transformer, then to LV switchboard probably with separate N-G depending on your reading of that exception in 250.30(A).

 

[tortuga]

1

 

[electrofelon]

My fee is reasonable, just keep updating the thread this time.

To summarize I think we are really discussing 3 options:

Can you attach a higher quality version?