250.20-250.21 480V Single Phase system grounding

[bobby mercier]

For a Step up (240V to 480V)/ Step down (480V to 120/240V) system supplying a building pretty far from the distributor. My understanding of 250.20 (B) tell me that i don't have to ground the 480V system but 250.21 (B) tell me taht i have to install a ground detectors.

Does my understanding is ok?

 

[kwired]

For a Step up (240V to 480V)/ Step down (480V to 120/240V) system supplying a building pretty far from the distributor. My understanding of 250.20 (B) tell me that i don't have to ground the 480V system but 250.21 (B) tell me taht i have to install a ground detectors.

Does my understanding is ok?

I did not read the sections you mentioned but consider that you do need an equipment grounding conductor between the two buildings whether you use a grounded or ungrounded system. May as well ground one of the secondary conductors of the step up transformer, it will cost less then a ground detector.

 

[bobby mercier]

I did not read the sections you mentioned but consider that you do need an equipment grounding conductor between the two buildings whether you use a grounded or ungrounded system. May as well ground one of the secondary conductors of the step up transformer, it will cost less then a ground detector.

Thanks!

A lot of people sees to be unconfortable to bound/ground ''H2'' of a 240 to 480V single phase step up transformer. But if you ask them to do a step up with a 120/240 to 14.4KW pole transformer, they will not hesitate to bound/ground one side of the 14.4kV.

Does the transformer type and/or location (on a pole) and/or voltage affect the way to bound/ground the secondary system when the transformer is use as a step up?

 

[kwired]

Thanks!

A lot of people sees to be unconfortable to bound/ground ''H2'' of a 240 to 480V single phase step up transformer. But if you ask them to do a step up with a 120/240 to 14.4KW pole transformer, they will not hesitate to bound/ground one side of the 14.4kV.

Does the transformer type and/or location (on a pole) and/or voltage affect the way to bound/ground the secondary system when the transformer is use as a step up?

I saw you ask same questions in a PM before I saw this and replied - check your messages.

 

[electrofelon]

I did not read the sections you mentioned but consider that you do need an equipment grounding conductor between the two buildings whether you use a grounded or ungrounded system. May as well ground one of the secondary conductors of the step up transformer, it will cost less then a ground detector.

One may be able to utilize 250.30(A)(1) exception #2 to avoid the SSBJ in the grounded version.

 

[Smart $]

One may be able to utilize 250.30(A)(1) exception #2 to avoid the SSBJ in the grounded version.

I believe the concern here is the "in between" of the step up/down scenario. I would assume there is no building or structure involved but I would utilize that exception as if there were. :happyyes:

Running a three-wire 3Ø delta secondary also permits the secondary conductors to be protected by the primary OCPD [240.21(C)(1)].

 

[electrofelon]

I believe the concern here is the "in between" of the step up/down scenario. I would assume there is no building or structure involved but I would utilize that exception as if there were. :happyyes:

Running a three-wire 3Ø delta secondary also permits the secondary conductors to be protected by the primary OCPD [240.21(C)(1)].

What is your opinion on the protection for the second (step down) transformer? This is a question that has come up several times (once by me) but I got no opinions.

 

[Smart $]

What is your opinion on the protection for the second (step down) transformer? This is a question that has come up several times (once by me) but I got no opinions.

Interesting question. If the secondary conductors are protected by the primary OCPD, I do not see why the step-down transformer primary cannot also be protected, provided the step-down transformer rating is equal or better than the step-up transformer.

Would I do it? Probably not. :angel:

 

[kwired]

One may be able to utilize 250.30(A)(1) exception #2 to avoid the SSBJ in the grounded version.

I forgot about that exception. Main condition is you must not have any other conductive paths between the two. You also must bond each end, so it about has to be a grounded system, if it were ungrounded system you still have to bond both ends, but only to the EGC, which would have to be a third conductor in that instance.