CT calculation
CT calculation
2
144x (Electrical)
(OP)
can anyone show me with an example how to calculate
the over dimensioning required for a CT in order to keep
it from saturating due to transient effects?
the over dimensioning required for a CT in order to keep
it from saturating due to transient effects?






RE: CT calculation
http://www.selinc.com/techpprs/6107.pdf
http://www.selinc.com/flyers/311lflyr.pdf
http://www.geindustrial.com/pm/ppt/bus2000.pdf
for more info
RE: CT calculation
RE: CT calculation
http://www.geindustrial.com/industrialsystems/meter/notes/GET-97D.pdf
for more info on a CT protection against surges, and errors due to harmonics under "Wave Form."
RE: CT calculation
1. Sutherland P. E. "Applying CTs with Digital Ground Relays," IEEE Industry Applications Magazine, Vol. 7, No. 2, pp 71-79, March/April 2001
Reference 1 indicates that the best solution is to design the system to prevent the line CTs from full saturation during external phase faults. So beware of various clandestine calculations!
RE: CT calculation
the dimensioning required for a CT in order to keep
it from saturating due to transient effects?
RE: CT calculation
RE: CT calculation
I have a copy of the 1976 edition of the Westinghouse Applied Protective Relaying book, which gives the following formula -
Transient saturation is avoided if :
Vk >= 6.28*I*R*T
Vk = CT kneepoint voltage
I= symmetrical secondary current, A RMS
R= total secondary resistance
T= dc time constant of the primary circuit in cycles
T=(Lp/Rp)*f
Lp = primary circuit inductance
Rp = primary circuit resistance
f = system frequency
This formula will give a reasonable approximation. More details are available from the folllowing reference: http://www.geindustrial.com/pm/notes/ger3973.pdf