Current Transformer Rating
Current Transformer Rating
(OP)
Hello,
What does it mean for a current transformer to be ext. 100%? Does that mean it allows for a continuous current of double it's rated current without any damage?
Thanks.
What does it mean for a current transformer to be ext. 100%? Does that mean it allows for a continuous current of double it's rated current without any damage?
Thanks.






RE: Current Transformer Rating
1) Maximum current value in order to limit the measuring accuracy [usually 5-10%] for a very short duration [seconds]. The limit in the IEEE standard is 20 times the CT primary current rating. Twenty times is also the preferred limit in the IEC standard.
2) Normal Current Rating (Ia) =Current which can be carried continuously without any current transformer part exceeding its normal and allowable maximum temperature.
3) Emergency Current Rating (Ie) =Current which can be carried for a specified period of time without any current transformer part exceeding its emergency allowable maximum temperature. For instance:
Percent of Adjusted Rated Continuous Current [Normal Allowable Maximum Temp.85 C degrees]:
Season: winter summer
Normal 120 100
Emergency: Greater Than 24 Hours 141 125
2 to 24 Hours 149 129
15 Minutes 175 159
For more information see:
ht
RE: Current Transformer Rating