Transformer differential relaying
Transformer differential relaying
(OP)
hi to everyone. this is my first post. and i have found the posts in this forum very informative.
i am trying to learn more about differential protection in general and i have not read much in depth about this. one particular question that i have in mind for now is about how to dimension the CTs for transformer differential protection.
Say we have a 2500kva, 13.8kv:480Y/277v transformer. The primary full load current Ip = 104.59A and the secondary full load current is Is = 3007.12A.
what should be the CT ratings be in this case? do these CTs matched in terms of the relaying class?
thanks.
i am trying to learn more about differential protection in general and i have not read much in depth about this. one particular question that i have in mind for now is about how to dimension the CTs for transformer differential protection.
Say we have a 2500kva, 13.8kv:480Y/277v transformer. The primary full load current Ip = 104.59A and the secondary full load current is Is = 3007.12A.
what should be the CT ratings be in this case? do these CTs matched in terms of the relaying class?
thanks.






RE: Transformer differential relaying
see following site:
http://www.selinc.com/techpprs/6025.pdf
(page 14 - 16) for example how to choose CT's
"Class X" CTs are used in diff. protection, this is special CTs used mainly in balanced protection systems (including restricted earth fault) where the system is sensitively dependent on CT accuracy.
RCC
RE: Transformer differential relaying
A good laundry list of application considerations for harmonic-restrained transformer diffs is a basic single-function relay booklet like: http://www.geindustrial.com/products/manuals/bdd/bdd.pdf
[Er, that would be kind of a small transformer to apply differential protection to. IEEE C37.91 suggests 10MVA.]
RE: Transformer differential relaying
james
RE: Transformer differential relaying
busbar - you are right. as for myself, i have never been seen any differential protection for this not so large power transformer - 2.5MVA. anyway, this is just an example that i have thought of as i could not relate this to my experience.
RE: Transformer differential relaying