Risk Assessment - Changing Taps on 30Y/O Oil Filled Transformer

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shoon

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Needing to increase the tap size on a 30 year old Federal Pioneer 25kv - 4160v transformer but unsure if there are any risks in doing so given the age of the transformer.

Given that it is an oil filled transformer I would speculate that the taps wouldn't be 'stuck' or have any risk of breaking. At worst, maybe the o ring on the external tap handle might leak.

Does anyone have any expertise in this area? Is it relatively safe to do so or given the age of the equipment is this considered high risk?
 
Every transformer I have seen says "de-energize before changing tap position". I have some 4160grdy/2400 transformers at home and I admit I have changed the taps energized but not under load. I can't really speak to how "bad" it is or to what could happen, but I would speculate it is more of an issue of being bad for the contacts and not so much a safety issue.
 
@shoon are you asking about the risk of shutting the transformer down, changing the tap settings, and having something go wrong preventing re-energizing?

How large is this transformer?

Just trying to anticipate the questions the HV guys will have....

Jon
 
electrofelon said:
Every transformer I have seen says "de-energize before changing tap position". I have some 4160grdy/2400 transformers at home and I admit I have changed the taps energized but not under load. I can't really speak to how "bad" it is or to what could happen, but I would speculate it is more of an issue of being bad for the contacts and not so much a safety issue.
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Thank you. To clarify for my situation- the transformer would be de-energized. Just wasn't sure if there was any potential for physical damage by changing taps.
winnie said:
@shoon are you asking about the risk of shutting the transformer down, changing the tap settings, and having something go wrong preventing re-energizing?

How large is this transformer?

Just trying to anticipate the questions the HV guys will have....

Jon
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Correct, exactly as you have stated. I am concerned about something going wrong during the de-energized tap change that might affect being able to re-energize.
It's nameplate states LV Amps: 312.27 @ 2.24 MVA
 
electrofelon said:
Yeah, I was talking about, and also assuming the OP was too, about pad Mount transformers that have an external tap selector.
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You're right, I missed it. "At worst, maybe the o ring on the external tap handle might leak."

I wonder whether they're break-before-make or make-before-break.
 
shoon said:
Needing to increase the tap size on a 30 year old Federal Pioneer 25kv - 4160v transformer but unsure if there are any risks in doing so given the age of the transformer.

Given that it is an oil filled transformer I would speculate that the taps wouldn't be 'stuck' or have any risk of breaking. At worst, maybe the o ring on the external tap handle might leak.

Does anyone have any expertise in this area? Is it relatively safe to do so or given the age of the equipment is this considered high risk?
Click to expand...
What size is the transformer? Has it been maintained? Do you know anything about the oil?

I did this with a 30-year-old 7.5 MVA, 69:12.47kV unit with no issues. But that transformer was maintained, and the oil was known to be in good condition.

My experience is that the tap-changing mechanisms are reliable.
 
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