Dist. Txf Short-Circuit : Stabilizing Winding - Electrician Talk - Professional Electrical Contractors Forum
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Old 06-01-2014, 09:30 AM   #1
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Unhappy Dist. Txf Short-Circuit : Stabilizing Winding

Hi All,

I am facing one critical matter where my energised (Vector group:ynYNd01) oil distribution transformer is down and basically the consultant and contractor disagreed with factory's view.
a) Factory made this transformer according to consultant spec, it was tested twice before energised.

b) Contractor used bear copper tape to earth it with our provided point at the bottom of the transformer and they also used another copper bear copper tape to earth the stabilizing winding point from the top of transformer (with both copper tape jointly touched on bottom and grounded. But the top stabilizing earth bar was touched with the side body of the transformer. The burn mark was showing at the point from stabilizing bar touched the body of txf.

c) We open up and lift the winding and saw some burn point from the bottom of the stabilizing winding which also burn the bottom structure steel of the transformer. Is already out of shape and touched the structure steel.

d) Factory engineer explained that it was the wrong earthing mathod that stabilizing shall use insulated copper to earth and shall not touch the body earth bar. It's already touched the body earth bar and stabilizing non-insulated touched the transformer top body created big flow of current force to cause the internal stabilizing winding to curve and touch the internal winding structual steel to spark....

e) Contractor forgot to install our provided Oil Thermometer (with contact), which is totally weird... I am totally shocked! and we dont know is this overheated.

Now, the consultant disagreed our view. Please help to look into this and advice us are we wrong in the factory explaination?
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Old 06-01-2014, 10:58 AM   #2
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Quote:
Originally Posted by joytuw View Post
Hi All,

I am facing one critical matter where my energised (Vector group:ynYNd01) oil distribution transformer is down and basically the consultant and contractor disagreed with factory's view.
a) Factory made this transformer according to consultant spec, it was tested twice before energised.

b) Contractor used bear copper tape to earth it with our provided point at the bottom of the transformer and they also used another copper bear copper tape to earth the stabilizing winding point from the top of transformer (with both copper tape jointly touched on bottom and grounded. But the top stabilizing earth bar was touched with the side body of the transformer. The burn mark was showing at the point from stabilizing bar touched the body of txf.

c) We open up and lift the winding and saw some burn point from the bottom of the stabilizing winding which also burn the bottom structure steel of the transformer. Is already out of shape and touched the structure steel.

d) Factory engineer explained that it was the wrong earthing mathod that stabilizing shall use insulated copper to earth and shall not touch the body earth bar. It's already touched the body earth bar and stabilizing non-insulated touched the transformer top body created big flow of current force to cause the internal stabilizing winding to curve and touch the internal winding structual steel to spark....

e) Contractor forgot to install our provided Oil Thermometer (with contact), which is totally weird... I am totally shocked! and we dont know is this overheated.

Now, the consultant disagreed our view. Please help to look into this and advice us are we wrong in the factory explaination?
Hello.

You should have an electrical engineer look over your transformer so you can get the right advice.

Welcome to the forum.
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Old 06-01-2014, 11:03 AM   #3
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Hi Black dog,

Did have a lot engineers around when we open up the winding... any view?
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Old 06-01-2014, 11:13 AM   #4
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Big John will hopefully be around to sort this out for you.
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Old 06-01-2014, 12:19 PM   #5
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Tertiary windings are a bit out of my league, but what you're describing doesn't make sense to me.

If you're solidly grounding your delta, all your earthing points are common, you're putting the ground strap at the same potential as your tank and everything else. Unless you had absolutely massive zero sequence current flow there should be no reason for a difference in potential between the top of the grounding point and the bottom and no reason for arcing.

Try asking the same question here,
a lot of those guys are actually transformer designers and would be better equipped to give you an answer.
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