NEC 110.34 for air break switches

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mhowlett

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I am working on the design of a project with three 69 kv air break switches which will be mounted horizontally on a substation structure. I'm trying to determine to what extent 110.34 applies to this application. If I follow the literal interpretation of Table 110.34(A), there would need to be at least 12 ft. separation between each switch. The switches will be connected in series, and it is impractical to maintain such distances. Does this table apply to air break switches in overhead applications?
 
mhowlett said:
I am working on the design of a project with three 69 kv air break switches which will be mounted horizontally on a substation structure. I'm trying to determine to what extent 110.34 applies to this application. If I follow the literal interpretation of Table 110.34(A), there would need to be at least 12 ft. separation between each switch. The switches will be connected in series, and it is impractical to maintain such distances. Does this table apply to air break switches in overhead applications?
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I think it primarily applies to ground level medium voltage equipment. Such that the human body of the person servicing that equipment has to be that distance away from the energized components or the enclosure for them. The table was made with the idea that the person servicing the equipment would use a fiberglass pole to operate on the live parts, at a safe working distance.

If it is already 20 ft above the person, you are already a safe working distance away from it.

It is certainly easier to defend your situation of pole-mounted air breaks, if you do separate them 12 ft. Does the manufacturer have any minimum separation requirements? I would expect that each switch needs a buffer zone in order to prevent stray arcs from passing from switch-to-switch.
 
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