Why CT Should Not Be Open Circuited?

This depends only on the CT and how it is made. Some current transformers with open secondary can indeed produce higher (dangerous) voltages. Especially while used with high currents.

Dear Aghvel,

you mention "saturation of the core". Can you explain it better? I imagine saturation can explain some clamping effect and/or dv/dt, producing higher voltages than according to the turn ratio.

But I can't agree with "current transformer from above is connected to a 480 volt...". You will not be able to apply such a voltage to the primary "winding" (one turn - in fact, a bar).

brgds

Snel

as you are new to CR4.. here is some advice.... try looking for past answers to this type of question in CR4, and there are lots.

I know that you don't JUST find CR4 on the internet, so as you are here, you know how to search... I suggest you do just that, search CR4. Then if you don't understand the answers you find, come back and ask for some clarity! Enjoy!

Maybe that's what started the fireball travelling down the power lines!

Dear Mr.bala009,

In simple terms, the voltage at the Secondary side will be multiplied by the CT Ratio,of the CT and may result in sever shock, arcing, even explosion.

Take an example of a CT for 3000/5 Amps, the ratio is 600, and if the Voltage is 420 in the Primary Side of CT, the Voltage in the Secondary side will be 420 x 600 = 2,52.000 volts, which is very dangerous.

DHAYANANDHAN.S

Repair problem one:

Sorry to respectfully disagree: 420 X 600 = 252,000. (that is the math) and the name I suggest is "times 1000 question marks"

How you will ever get 420 Volts over, say 1 or 2 inches cable through a CT is a big mystery for me.

A CT is the abbreviation of "Current Transformer", where current is interpreted as amperage, or amperes (AC). A current transformer in most cases only starts to be a transformer as soon as you put your primary winding through the core center.

And from then on it transforms current, considered you have a load to transport it to (through the secondary). An open secondary will transport any possible current into the air (and the air is very thin to take any)

Please try it out.

Now to answer the OP's OP:

A CT should not be open circuited, because it will not be a CT, but a coil and will appear to not help you measure current.

Thank you Mr.dvmdsc, for your reply/note.

What i have learnt during study days - taught by our Professors, picked up by us and continue to talk in the same line.

I request you to explain more details hre so tat others also can understand (or) can be sent through CR4 Personal Messaging.

Thanks,

DHAYANANDHAN.S

Hi Sir,

You are not the only one in doubt. CT's will be discussed long time from now in the future. Note that there can always be a risk, working with these and leave the choice to specialists, especially when it comes to higher currents. The reply of poster #3 you can read in the link that Lyn posted. I cannot afford to believe everything someone writes down on the internet. It should be obviously clear to everyone that uses CT's to work according the directions, rules and regulations.

CT's are not to be used in saturation conditions (i.e. undersized). Once you get to install CT's you wonder why they are so big and heavy? From the design they have a big margin, so that saturation does not occur in normal conditions.

If this matter is interesting to you, pls check the internet, especially for CT core in saturation. Some problems may happen indeed, but these are so particular that I do not want to put values (or write down a formula) on voltages over an open secondary winding. These are so specific to the hic et nunc situation created.

Always work with caution, hope and think for the best, but prepare for the worst. Regards. D