CT Burden and Class

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

hope this help you........