CT burden

check here http://www.kele.com/tech/monitor/Power/TRefPM5.html

CT burden is the load imposed on CT secondary during operation.

The burden is mentioned as x-VA for the CT.

In the case of Measuring Current transformer, the burden depends on the connected meters and quantity of meters on the secondary ie no of Ammeters,KWh meters,Kvar metrs,Kwh meters, transducers and also the connectiong cable burden

(IxIxRof cableX 2L)to metering shall be taken into account.

where 2L is the to &fro distance of cable length-L from CT to metering circuits

R=is the resistance of unit length of connecting cable

I=secondary current of CT

Total burden of Measuring CT=Connecting cable Burdeni n VA + sum of Meters Burden in VA

Note Meters burden can be obtained from manufacturer catalogue

Selected CT burden shall be more than the calculated burden.

In the case of Protection CTs the burden is calculated in the same way as above except the burden of individual protective relays burden shall be considered instead of meters.The connecting cable burden is calculated in the same way as metering CT

Total burden of Protection CT=Connecting cable Burdeni n VA + sum of Protective relays Burden in VA.

Selected CT burden shall be more than the calculated burden

Note Protective relays burden can be obtained from manufacturer catalogue

V.Ambarani

Dear Mr.Ambarani,

Thanks for your detailed reply.My doubt has been cleared by your answer.

regards,

kp

dear sir,

thank you so much for the above information on c.t. burden.i am really indebted to you.

thankyou,

warm regards,

aftab,

electrical and electronics engineer

Dear sir,

thanking you ....

Impedance of a circuuit connected to CT secondary is called Burden of CT and expressed always in VA(Volt Amper).

But what happened if the CT is over burden i.e if CT own burden is 20 VA where as the over all burden CT has to bear is 25 by adding protection and metering burden.

regards

Manzoor Alam

the ct moves towards saturation, resulting waveform moves away from a sine wave and hence the accuracy stated in the ct specification is no longer correct