Current transformers

[devendrasp]

Is there any standard (or non standard yet tested) method for reversing the saturation (Desaturation)of the core of a saturated CT ? In this case the CT is 33kv one with the protection core saturated.

 

[RRaghunath]

There are no codes to guide demagnetising of a saturated CT core, to my knowledge. CT manufacturer's should be able to provide you a write up, though. A couple of suggestions are,
A CT left idle for some time gets demagnetised (without doing any thing in particular).
Trace the Hysteresis curve of the CT core starting with its knee point voltage and then repeating the same several times, reducing the peak applied voltage little by little every time. This method id used if CT needs to be demagnetised in a short time and put back in service.

 

[cranky108]

Try a shorting the primary, and backfeed a current of about 15 amps, and gradually reduce the current (ac current) to zero.

 

[stevenal]

IEEE C57.13.1-2006 describes the procedure, and it it done with an open primary.

A good CT test unit will do the job automatically. This is a plus, because doing it manually can be challenging. You must hit the knee point without overshooting into the trip your source region.

 

[stevenal]

I mean't to say "it is", not "it it."