Transformer Internal Fault

Eh? How can more <...current flow into it than leave it...>?

This statement doesn't make sense.

that's what happens in case of internal fault like inter-turn fault and i am also not able to understand that.

Current travels at the speed of light, right? So when it enters the wire, it hasn't yet emerged from the other end? Thus for some few nanoseconds, maybe the OP is right? There are other confusions, though.

may be,any other thoughts??????

No, that's probably the only thought I have about this.

Power in is compared to power out by the use of CT's of different ratios. Have a look at http://electricalandelectronics.org/2009/03/19/differential-protection-in-transformers/

It also explains how the CT's are connected to balance the difference in phase angles.

thanks for the link ,it provides quite useful information but doesn't quite answer my question exactly,Experts please help,the answer is not in any textbook!

Regards,

Sohan

It won't be in any text book, you're looking for something that doesn't exist.

A step down transformer with no load connected to the secondary. Based on your 1/1000 ratio.

If there is an internal fault on the primary winding which draws 3A, with no fault on the secondary, where is your 3000A going to go? The 3A will just create heat "inside" the transformer.

The operative words are "internal fault"

the transformer is loaded,i took 1000/1 ratio to just make my question clear.

In case of internal faults , only the source and the winding till the point of fault will drive lrage currents. Suppose if two tranforrmers are in parallel and internal fault occurs in one transformer, the other transformer will start feeding the fault location. But usually, in grids, they have directional overcurrent & earth fault protection for Secondary side back up protection. If lrage currents start feeding into transformer in reverse (through secondary sise), it will trip the faulty transformer alone. So in your case the fault current flows depending upon the fault. If the fault location is exact near to transformer sec ( inside diff. protected area), it will draw large current.

Hai,

Iam M.Ayyavaru working with HBL Power systems Ltd Hyd.

What you said is right, if any problem in trmr it trips by over load protector, but there is no rule that secondary current must be as per transformer ratio at the time of fault,fault may happened at any winding.1) If fault accrued in pry winding why secondary current increase in this case no chance to increase secondary current.2) If fault accured in secondary winding according to secondary fault current pry current shoot up.I hope your dought may be cleared.

Regards,

M.Ayyavaru.

As already said: If the fault is internal like shorted windings, the ratio will change accordingly.

Also, the current is flowing internally and does not come out from the secondary terminals. This is in both cases primary or secondary winding faults.

So, there will allways be an excess unbalanced power into the transformer against the output power from the secondary. The Normal internal losses are known and represent a small percentage of the total power input. These are taken into considerarion.