connection of dual core current transformer
connection of dual core current transformer
(OP)
i would like to know the information about current trasformer. I have dual core current transformer with three terminals viz s1, s2 and s3. s1 is common and earthed. Between s1 and s2 i get ratio of 200/1 and between s2 and s3 i get ratio of 400/1. if i would like to use s1 and s2 with ratio of 200/1, what should i do with s3 terminal. is it nescessary toshort s3 and s2? or s3 should be earthed? please guide..






RE: connection of dual core current transformer
RE: connection of dual core current transformer
it is single core CT only. Can you any backup document which will support your answer. Because I am also of the same opinion but not getting any backup. Please provide if u have.. Once agin thanks a lot...
RE: connection of dual core current transformer
You will also want to have one of the terminals earthed. See IEEE C57.13.3.
RE: connection of dual core current transformer
I'm also recommend connect S1,S2,S3 to terminals and earthed one of them on terminal, not on the CT.
In future:
1. You can change connection to relay ( or meter) easily.
2. You can disconnect earth easily (for megger test).
Earth of CT it is safety requrements.
You must put earth only in one point ( in case of differntial protection is critical).
Earth connection and option for short of CT terminals you must put in first star point of CT connection (near to CT).
RE: connection of dual core current transformer
RE: connection of dual core current transformer
For a muli-core/winding CT, each winding would be marked with a different letter and there would have to be at least 4 terminals.
RE: connection of dual core current transformer
S1:S2 is 200:1
S2:S3 is 400:1
Note S2 to S3 appears to be the full winding, which implies S1 is the center tap. I would have expected S2 to be the center tap. Or maybe you misreported the matter.
Nothing will be as definitive as going back to the mfr and asking for a document.
RE: connection of dual core current transformer
In this example, the full winding 'could' be 600:1. We make some CTs like that for certain customers, although it's pretty rare.
RE: connection of dual core current transformer
RE: connection of dual core current transformer
Assume the CT is a window or bushing type with one primary turn and 400 secondary turns, 200 from S1-S2 and 200 from S2-S3.
Say you have a primary current of 400A (400 ampere-turns)and you are using S1-S2 for a 200/1 ratio. With S2-S3 open, you will get 2A in the S1-S2 circuit, for 2·200=400 ampere-turns.
If you connect something to S2-S3, there will be current in S1-S2 and S2-S3, split in some manner based on internal and external burdens of each circuit. If S2-S3 is shorted (nearly zero burden) and S1-S2 has a burden significantly higher than the internal CT winding resistance, then all of the 400 ampere-turns will occur in the shorted section of the winding. You will get almost 2A (2·200=400 ampere-turns) from S2-S3 and practically no current from S1-S2.
RE: connection of dual core current transformer
I wouls like add to Jghrist explanation some pict.
http://tinypic.com/view.php?pic=6frr41s
Regards.
Slava
RE: connection of dual core current transformer
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It may be like this in theory and practice, but in real life it is completely different.
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