current transformer size

[bibi1964]

hi
Is there a table of current transformer size by connection size?

 

[marks1080]

Protection? Metering? For protection you generally size the CT based on available fault currents such that the CT doesn't saturate before the protection can operate.

 

[HamburgerHelper]

Sizing it for no saturation can make for a big ct. It takes a substantial amount of saturation to greatly impact the fundemental.

https://www.l-3.com/wp-content/uploads/2010/10/CT-SAT-Calculator-PSRC.xls

There is an IEEE standard that covers this but I wouldn't change out a CT if I a small amount of clipping clipping. All my comments are for protect CTs. Metering should be sized to not saturate.


All this though doesn't apply for high impedance bus differential which uses ct saturation to guard against out of zone faults. Those CTs do have to be sized to not saturate for in zone faults.



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