20 times rated secondary current for CT?
20 times rated secondary current for CT?
(OP)
Why is the CT error specified in terms of 20 times rated sec current? What is the signifance of this number? Can be it be derived performing calculations on basic CT model?
Thanks in advance
Thanks in advance






RE: 20 times rated secondary current for CT?
RE: 20 times rated secondary current for CT?
A protection CT is designed to maintain accuracy within specified limits of error up to a certain primary current. This current divided by the rated current is termed the accuracy limit factor. (ALF) Standard ALF-values are 5, 10, 15, 20 and 30.
In your case the ALF-value is 20. Thus, at 20 times rated current, you'll have a certain composite error, normally 5% or 10%
During a short-circuit is the fault current many times the normal rated current. Adequate protection depend on the effectiveness of the CT during this fault period.
See also standard BS 3938:1973
Regards
Ralph
RE: 20 times rated secondary current for CT?
Regards
Ralph
RE: 20 times rated secondary current for CT?