The Electrical Contractor Network

ECN Electrical Forum
Discussion Forums for Electricians, Inspectors and Related Professionals

Books, Tools and Test Equipment for Electrical and Construction Trades

Register Now!

Register Now!

We want your input!

Featured:
   

2017 NEC and Related
2017 NEC
Now Available!

   
Recent Posts
Safety at heights?
by Trumpy
Today at 05:25 AM
Old Bath Fan
by gfretwell
Today at 01:38 AM
Search Function
by Webmaster
Yesterday at 11:13 PM
Forum Software Upgrade coming soon...
by Webmaster
Yesterday at 09:17 PM
ESA Arc flash course
by frank
Yesterday at 04:25 PM
New in the Gallery:
Desk-mounted "power-board"
Top Posters (30 Days)
Webmaster 30
HotLine1 21
Ruben Rocha 16
Trumpy 13
gfretwell 13
Who's Online
0 registered (), 0 Guests and 172 Spiders online.
Key: Admin, Global Mod, Mod
Topic Options
Rate This Topic
#205512 - 02/28/12 07:36 AM dry type transformer failure
Danny00915 Offline
New Member

Registered: 02/23/12
Posts: 1
Loc: Singapore
I have a 50kVA dry type transformer which had failed, with rating:

1. Input (LV, primary winding): 400V, 72.17A
2. Output (HV, secondary winding): 21.5kV, 1.34A

The failed area was found to be the HV winding, where short circuit of winding and sign of local overheating was observed . Calculations showed no overload to input or output.

What would have cause the overheating? probable cause of the failure?

Top
Work Gear for Electricians and the Trades

Work Gear for Electricians and the Trades
Work Gear for Electricians and the Trades
Arc Flash Clothing, Gloves, KneePads, Tool Belts, Pouches, Tool Carriers, etc. etc....

#205526 - 02/29/12 12:18 PM Re: dry type transformer failure [Re: Danny00915]
geoff in UK Offline
Member

Registered: 12/30/02
Posts: 177
Loc: UK
Simple transformer insulation failure? It only takes one turn to short out and rapid overheating follows causing progressively more insulation failure.
Possible causes? Weak insulation since manufacture, moisture ingress, vibration, transient voltage surge, hotter than designed operating environment, - I'm sure there are more I can't just think of.

Top
#205527 - 02/29/12 02:30 PM Re: dry type transformer failure [Re: Danny00915]
gfretwell Offline


Member

Registered: 07/20/04
Posts: 9063
Loc: Estero,Fl,usa
Is it getting plenty of air? These things, in confined space, can heat up quickly.
_________________________
Greg Fretwell

Top
#205528 - 02/29/12 07:22 PM Re: dry type transformer failure [Re: Danny00915]
HotLine1 Offline


Member

Registered: 04/03/02
Posts: 6831
Loc: Brick, NJ USA
100% agree with that Greg> I remember a plant where some employees used a 75KVA for a lunch warmer with help from some cardboard & welding screen curtains! A situation that could have become a njghtmare.
_________________________
John

Top
#205555 - 03/03/12 02:31 PM Re: dry type transformer failure [Re: Danny00915]
Lostazhell Offline
Member

Registered: 02/21/04
Posts: 1248
Loc: Bakersfield, CA (Originally Or...
We had an old Westinghouse padmount 12kv pri 480V sec 1000kva that inadvertently was loaded up with >1600 hp in oil pumping units & steam genset pumps & blowers.. It ran this way for quite some time & wasn't discovered until we ran into some low voltage issues in a control room... The load was divided up with 2 banks of 167s added. The padmount still runs part of the field..

Top


ECN Electrical Forums - sponsored by Electrical Contractor Network - Electrical and Code Related Discussion for Electrical Contractors, Electricians, Inspectors, Instructors, Engineers and other related Professionals