13.8kV transformer working clearances

[Dale001289]

Do the working clearances shown in NEC 110 apply to oil fill power transformers?
Client has installed a chain link fence approximately 3 feet from the 13.8kV primary side of a 3MVA power transformer. The primary has two doors that can be opened manually however it does have locking capability -
This seems too close to me

 

[Isaiah]

Do the working clearances shown in NEC 110 apply to oil fill power transformers?
Client has installed a chain link fence approximately 3 feet from the 13.8kV primary side of a 3MVA power transformer. The primary has two doors that can be opened manually however it does have locking capability -
This seems too close to me

5’ min per NFPA 70E


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[ron]

The working clearance is


The distance from a fence is

 

[Isaiah]

The working clearance is
View attachment 2564383

The distance from a fence is
View attachment 2564385

The fence represents a condition 2.
So why is the distance XFMR to fence twice the amount as the working clearance?
Doesn’t seem to make sense to me.


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[jim dungar]

Fencing around enclosed equipment, like padmount transformers, is different than what is required for open air equipment.

 

[Isaiah]

Fencing around enclosed equipment, like padmount transformers, is different than what is required for open air equipment.

In other words the 10’ distance only applies to open air connections such as an outdoor ‘utility’ type substation transformer?


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[don_resqcapt19]

The fence represents a condition 2.
So why is the distance XFMR to fence twice the amount as the working clearance?
Doesn’t seem to make sense to me.


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The code text above Table 110.31 says that that table applies to other than equipment described in 110.31(D). The equipment described in that first level subdivision is all enclosed equipment. It appears that the transformer in this thread is enclosed equipment.

 

[busman]

If you need to pull an elbow with a 6' shotgun stick, you will want the whole 10'

Mark

 

[Isaiah]

If you need to pull an elbow with a 6' shotgun stick, you will want the whole 10'

Mark

Would the shotgun stick be needed for the enclosed 13.8kV primary side XFMR ?


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[busman]

Would the shotgun stick be needed for the enclosed 13.8kV primary side XFMR ?


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Maybe it's just me, but I wouldn't pull ANY energized MV elbow directly with my hands, even gloved. Also, if the elbow is difficult, you may need an impact elbow puller which are usually about 6' long.

Mark