NEC 110.34(B) Seperating low voltage equipment from transformer

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svenoaks

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How do I categorize a medium-voltage to low-voltage substation transformer? It seems impossible to meet this section if you categorize the transformer as a medium-voltage piece of equipment, unless you're always meeting the tap rule for the secondary protection. For example if I put the 13.2kV- 480/277v substation in a room it seems the 480v secondary protection would need to go in a separate room or be fenced off?
 
svenoaks said:
How do I categorize a medium-voltage to low-voltage substation transformer? It seems impossible to meet this section if you categorize the transformer as a medium-voltage piece of equipment, unless you're always meeting the tap rule for the secondary protection. For example if I put the 13.2kV- 480/277v substation in a room it seems the 480v secondary protection would need to go in a separate room or be fenced off?
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I think the key is the word "exposed".
 
svenoaks said:
Wouldn't you have exposed live parts if you were servicing the equipment when energized (where working clearances apply)?
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I don't see how the term "exposed" can have any real meaning if it only applies when something is taken apart for servicing since everything would then always be considered "exposed".

Exposed (as applied to live parts). Capable of being inadvertently
touched or approached nearer than a safe distance by a
person. (CMP-1)
Informational Note: This term applies to parts that are not suitably
guarded, isolated, or insulated.
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petersonra said:
I don't see how the term "exposed" can have any real meaning if it only applies when something is taken apart for servicing since everything would then always be considered "exposed".
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The sections on Working Space such as 110.34(A) and 110.26(A) both indicate that the working space is to be measured from "exposed live parts" on one side of the working space and applies when "exposed live parts" are on one or both sides of the space. So in that context "exposed live parts" basically does mean all equipment, and I don't see why it wouldn't apply to 110.34(B) as well.
 
My point was more along the lines of "exposed" can't possibly mean when something is torn apart for servicing since then "exposed" would apply to everything.
 
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