I encountered a problem in measuring electrical energy using a multi ratio current transformer (CT). The catalogue of CTs is unavailable.

I have little information about the type of CT I am using. I have several questions about this matter. Firstly, the CT I work with has 7 connections: X7,100,200,300,400,500&600.

The connection for ratio 100/5 was on X7 & 100. Something that is confusing me is that X7 a common connector and if connection X7 to 100 measures 100/5, are other windings from 200 to 600 in circuit or open? If they are in circuit how does it produce a 100/5 ratio, and if they are open how it that possible for a CT?

Secondly, the power transformer has delta connections and the CT connection is a Star. After I have connected the meter to the CT I get an error in energy metering. Is it possible that this error is due to the star connection of the CT and should it be a delta connection, as for the power transformer?

Its impossible to change the CT connection to delta. Can I define any coefficient factor to remove this error with out changing the circuits?

The power transformer ratio is 14400/3300, with a delta connection and the CT's ratio is 200/5, with star connection. enter image description here


I've encountered this problem before.

This problem didn't depend on the connection of your power transformer.

This problem happens when meter coefficients (depend on your CT's and PT's ratios)are inappropriate.

The note is this:Check your circuits node and use KCL law to calculate the powers in node.

Best regards


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