CT ratio problem

Dear All,
I am new for Knowledge of CT ratio, my question is What is ct ratio ? How it use?


suppose i have new Schneider EM 6400 ,Energy meter ,during setting it is necessary to enter CT ratio for getting correct reading, But i don't know from where i got CT ratio

I.e From where or who give me CT ratio

Hi Amol,

CT means Current transformers. These CTs, are transformers used to step down the current level of high-power transmission systems to measure or monitor the current levels. CTs are required because standard current measuring devices, in your case you are using the Schneider EM 6400 energy meter, are not configured to measure high-current levels. As a consequence, engineers use CTs to step down the current levels to measure it. Once measured, they use the current transformer ratio, or CT ratio, to calculate the actual current from the measured current.

I just googled this info so if you need more references, it is easy to find a lot of them. To start of, here's the link a how to measure or determine CT ratio.

http://www.ehow.com/how_8475215_calculate-ct-ratio.html

Hope it helps.

Kind Regards,
Sardiah

Current transformers where the secondary current under normal operation is practically proportional to the primary current.

Voltages and currents can be very large in magnitude. The voltage from at home is 120V or 240V... but the voltage on distribution lines or feeders can be 12,400V or 24,00V or 33,00V...

If you use a blow dryer at home, it will use 10A of current... but what is the current on the feeder at 12,400V? A lot more!

A current transformer is an induction device that converts a very large amount of current to a smaller current... the smaller current might be 10 times smaller... How much smaller the current is depends on the CT Ratio... if the CT ratio is 100... than 1000A will be converted to 100A... and so fourth.

CT's converts a higher current to a smaller and more manageable current... CT ratio is the number of primary winding turns divided by the number of secondary winding turns... so CT ratio of 100 ... 125A is a primary value and 1.25A is a secondary value.

Check out this video tutorial for an idea of how these transformers work. http://gpac.link/1GdGRSQ

http://generalpac.com has a good host of videos for power systems stuff