how to calculate the knee point voltage of current
transformer?
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Answer Posted / puneet prashar
Knee Voltage=2X Earth Fault current(RCT + RW)/CT
Trasformation ratio
Where
RCT= CT impedeance as per manufacture1.02
RW = Wire resistance as per manufactre
say.oo32/metre then RW= 2X 200mtr X .0032
CT transformation ratio= 4000/1=4000
4000/5=800
VKnee= 2X58000(1.02+1.28)/4000 or 800 depending upon ct used
Vknee= 66.7v
Vknee> relay stability Voltage
Relay stability voltage formula will be given by relay
manufacturer as every relar manufacturer has their own formulas
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