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Old 03-20-2019, 05:48 PM   #1
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Default question: how you guys to check the transformer after wiring up?

as we know, there are continuity between the phases for the primary side and the secondary side, like H1 to H2, X1 to X2, X3 to X0, etc

the question is after wiring the transformer up, how to check if the transformer is OK? I mean no short circuit, no ground fault, I turn on the transformer, it will work instead of blowing up
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Old 03-20-2019, 06:32 PM   #2
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In production work, I just stand clear.

( I never heat up a (feeder power) transformer with a connected load. )

In such a case a bolted-short will pop a fuse or a breaker in a flash.

The usual fiasco in Service gear: loose bolts// forgotten tools.

The other issue: some transformers vibrate too much as delivered.

They can be quieted down by tweaking their mounting bolts. This involves powering down and pulling all of the covering panels off. Usually you have to come at the relevant bolts from both directions.

If your transformer is too noisy -- contact the factory for advice. Their tech desk is as busy as a Maytag repairman.
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Old 03-20-2019, 08:37 PM   #3
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Prior to terminating we megger the transformer and feeder separately. Depending on the specifications we will also TTR the transformer and finally, use a Tilt II

https://www.amazon.com/Greenlee-TL-M...ag=googhydr-20

I am never concerned about what we energize because we test everything prior to powering up.
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Old 03-20-2019, 09:04 PM   #4
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under 5 grand we megger then power up and test before closing load side breakers. Anything more expensive we bring in someone like brian who has invested in the tools and training to do the work as the cost of the tools and the learning curve is more hassle then its worth.
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Old 03-20-2019, 09:31 PM   #5
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Originally Posted by brian john View Post
Prior to terminating we megger the transformer and feeder separately. Depending on the specifications we will also TTR the transformer and finally, use a Tilt II

https://www.amazon.com/Greenlee-TL-M...ag=googhydr-20

I am never concerned about what we energize because we test everything prior to powering up.
Tilt II really works? is it any other similar tool like Tilt II?
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Old 03-20-2019, 09:33 PM   #6
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under 5 grand we megger then power up and test before closing load side breakers. Anything more expensive we bring in someone like brian who has invested in the tools and training to do the work as the cost of the tools and the learning curve is more hassle then its worth.
how to use the megger to test the transformer? can you describe the details how you do it?
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Old 03-20-2019, 09:51 PM   #7
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as we know, there are continuity between the phases for the primary side and the secondary side, like H1 to H2, X1 to X2, X3 to X0, etc

the question is after wiring the transformer up, how to check if the transformer is OK? I mean no short circuit, no ground fault, I turn on the transformer, it will work instead of blowing up

I turn the breaker on.


Off the top of my head, I can only think of one time in the last 14 years that we got one bad from the factory. And we install quite a few transformers per year.


So for that reason, with the VERY low failure rate from the factory, I don't spend any time megging before commissioning.
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Old 03-20-2019, 10:34 PM   #8
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how to use the megger to test the transformer? can you describe the details how you do it?
Megger Primary to Ground

Disconnect the neutral to ground bond and Megger Secondary to Ground

Megger Primary to Secondary
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Old 03-21-2019, 06:19 AM   #9
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I turn the breaker on.


Off the top of my head, I can only think of one time in the last 14 years that we got one bad from the factory. And we install quite a few transformers per year.


So for that reason, with the VERY low failure rate from the factory, I don't spend any time megging before commissioning.
I must admit i have never seen one fail either. Years ago i did see a new 25k/480v leak oil from the bushing. The install window was small so having the rep got us priority repair in place services. Had the rep not been on site we might have re-installed the old one.
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Old 03-21-2019, 07:47 AM   #10
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I must admit i have never seen one fail either. Years ago i did see a new 25k/480v leak oil from the bushing. The install window was small so having the rep got us priority repair in place services. Had the rep not been on site we might have re-installed the old one.
Only failure I remember on start up was an EC called with an issue, they had parallel feeds on the primary and they screwed up the feeder identification, nothing with the transformer. Not even a boom the Main CB kept tripping (they closed it 3 times and in the end had to replace the CB.

But in my opinion still worth the 5 minutes, it takes to test
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Old 03-21-2019, 05:34 PM   #11
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Megger Primary to Ground

Disconnect the neutral to ground bond and Megger Secondary to Ground

Megger Primary to Secondary
but that only prevent the ground fault

what about phase to phase short,

like H1 to H2, X1 to X3 short
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Old 03-21-2019, 05:53 PM   #12
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but that only prevent the ground fault

what about phase to phase short,

like H1 to H2, X1 to X3 short
The most practical method is to check the wires with at least an ohm meter, (a megger is better) both line and load, phase to phase and phase to ground before terminating the transformer.
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Old 03-21-2019, 06:03 PM   #13
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but that only prevent the ground fault

what about phase to phase short,

like H1 to H2, X1 to X3 short
Just pull out your favor tool .,, megger ., that will show up when you do the test on megger.

I only got 2 bad one brand new over the years so it was super rare for me to see new one bad straight from factory.

But used one that you need to test more deeper and need more specialist tool like what Brain John do have and Zac I think he deal with too if I recall it correct.
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Old 03-22-2019, 09:47 AM   #14
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Megger used xformers, new ones I rely on the overcurrent protection. I don't recall ever having a problem.
I had a customer roll a new one down a set of stairs when it fell off the dolly. It still tested fine but I was standing clear when we energized it.


Tim.
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Old 03-22-2019, 09:57 AM   #15
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Get everyone out of the Electrical room, have an apprentice punch 911 into his phone and hover his finger over the send button, turn on the breaker with a broomstick, breathe a sigh of relief and go for lunch.

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