×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Power Transformer Through Faults
3

Power Transformer Through Faults

Power Transformer Through Faults

(OP)
I am interested in two aspects of Power Transformer Through Faults:

First, Have you had a transformer failure that was attributed to the aggregate accumulation of transformer through faults over the course of time?  If so I would be interested in the details.

Second, I am interested in knowing of effective formal programmatic plans that identify and evaluate the aggregate effects of transformer through faults as a fault preventation and mitigation measure.

Thanks for your time.

RE: Power Transformer Through Faults

Research assignment??

RE: Power Transformer Through Faults

(OP)
Just due diligence.  I have used some industry search engines and am trying to make the case that this phenomena happens more frequently than many people realize and want to lay out a proposed program for contending with this phenomena.

RE: Power Transformer Through Faults

The average number of through faults will vary significantly depending on the transformer application.  Distribution substation transformers are normally subjected to a high number of through faults during the transformer life, while many industrial/commercial transformers will see a limited number.

It is difficult to determine if a transformer failed due to excessive through-faults since the damage done is cumulative.  

In a few cases, a single through-fault will destroy a transformer due to breaker failure.  But this is rare.  Normally it is the combined effect of numerous through-faults over many years (along with transformer overloading).  

There no question that through-faults damage transformers - that's why ANSI establishes transformer damage curves.  

RE: Power Transformer Through Faults

I've seen transfomrer winding failures on through-faults.  Since the protection was coordinated with the transformer I'd say the through fault caused the failure (telescoping winding failure - turn-to-turn).  That's why I've started requesting keyed windings or CTC for winding conductors.  I feel the greater surface area on the CTC provides better mechanical performance in fault conditions.  Any of you transformer guru's - please correct me if I'm wrong.

RE: Power Transformer Through Faults

The short circuit current withstand strength of transformer depends on the magnitude of it and also the number of faults during a time period.It is well accepted that in the life of a tranfsormer it is very rare that the unit will see the worst assymetric  SC current on it as it depends on the system fault level(rarely it is infinitive and always system impedance will  be limiting  the current. Maximum assymetry (up to 2.6 times ) will occur only in case fault happens when sinusoidal voltage is near to zero)

Number of faults do have an effect on the SC withstand strength of transformer.Certain types of  transformers have to meet several faults in a day eg : Rail Traction track side transformers supplying power to overhead  lines,transformers supplying power to  steel arc furnaces.Such transformers are specially made and  prototype unit is short circuit tested at high Power laborataries.

Extra Short circuit withstand  strength is built in to transformers by special design/manufacturing and processing measures.CTC(continuously transposed cable)will not add any SC withstand strength.In fact SC strength is less due to smaller dimensions of the several parallel enamelled  conductors constituting the CTC.But special CTC (with hardened conductors and with additional semi cured coating over enamelled conductors-which  during drying process will cure and bond all conductors together giving higher buckling strength)will give extra mechanical strength for inner windings to with stand buckling forces experienced during fault current flow.

RE: Power Transformer Through Faults

See IEEE guide for liquid-immersed transformer through-fault-current duration, IEEE Std C57.109-1993.

 

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources