Transfromer shutdown saftety procedure

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MrJLH

Senior Member
Location
CO
Not asking anyone to do this for me but just looking for some help and pointers.

I have a 500kVA 13.8kV to 480V with primary side over current protection only. The transforme secondary feeds directly to a bus duct.

I need to write a procedure to safely de-energize the transformer so work can be done on the bus duct.

What saftety factors do i need to consider? Can the scondary conductors just be removed after de-energization, and work can begin?

Take it easy on me please as I'am a "noob"

Thanks
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
From a utility substation perspective.....Primary would need a visible open. That means air break switch or solid blade disconnects. If from a transformer, elbows pulled and stood off, fuses removed, etc. Grounds on primary after de-energizing. Visible opens also on secondary for any possible backfeeds. The basic rule....identify, isolate, test and ground. If it ain't grounded, it ain't dead. An open breaker is usually not a visible open. Tags on everything. Companies may have different procedures, but the basics are the same.
 

MrJLH

Senior Member
Location
CO
From a utility substation perspective.....Primary would need a visible open. That means air break switch or solid blade disconnects. If from a transformer, elbows pulled and stood off, fuses removed, etc. Grounds on primary after de-energizing. Visible opens also on secondary for any possible backfeeds. The basic rule....identify, isolate, test and ground. If it ain't grounded, it ain't dead. An open breaker is usually not a visible open. Tags on everything. Companies may have different procedures, but the basics are the same.

Thanks for the response!
My company is the owner of the transformer. There is only a primary disconnect. No secondary disconnect , this was from a really really old installation. Work is being done on a switchrack down stream of the transformer.
Arcflash is 48cal/cm^2 @ 18", AFB 18ft


Can the ground set be applied to the transformer priamry?
 
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MrJLH

Senior Member
Location
CO
Is there an arc flash danger after the transforme has been de-energized?

Would the core not still have flux inside that could contribute to this?

How long would it take for any residual energy to bleed off?

I have been trying to find some white papers on this but have had no luck. My fear is that an arc flash will occur when the field tech is applying the voltage test on the transforme secondary.
 

MrJLH

Senior Member
Location
CO
Is there an arc flash danger after the transforme has been de-energized?

Would the core not still have flux inside that could contribute to this?

How long would it take for any residual energy to bleed off?

I have been trying to find some white papers on this but have had no luck. My fear is that an arc flash will occur when the field tech is applying the voltage test on the transforme secondary.


Edit line item #1 from de-energized to disconenct from primary
 
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