Current Transformers

Hi,

Current transformers are just like a normal transformer, but here we concentrate on the current for measuring. On the secondary, we get current rating of consider as 5 Amp.

On Primary, it as 200 Amp, we use cts for convenience in measuring the high currents, but on the secondary voltage is very high? Or not if it is high means in what range generally it will be of 130 kV transmission lines? Is it harmful for the relays or breakers connected to this cts or not?

http://www.pearsonelectronics.com/pdf/1423.pdf

The current transformer shown in the link above has an output of 0.001V/A and is rated for 2500 A RMS. With proper insulation it can be used on a 130 kV transmission line and at 200 amps will output 0.2 volts.

Mr. David here on cts the primary turns are very less in number and the secondary turns are very high, in general a transformer having high turns means voltage is high and vice versa. Is this theory applicable to cts are not??????

Yes it is applicable. A "standard" Pearson 1 Volt/amp current transformer has a 1-turn primary and a 50-turn secondary that is terminated into 50 ohms. 1 amp through the primary induces 0.02 amps through the 50 ohm resistor resulting in a 1 volt output.

The insertion impedance, which is the series impedance of the 1-turn primary, is (50 ohms)/(turns squared) = 50/2500 = 0.02 ohms.

thanks for your explanation