Current Transformer

It depends on the current transformer. I have noticed that for open CT's, used in electronic meters and smart meters on grids up to 240 VAC about NOTHING happens.

I have many open CT's that do not even produce 10 Volts without a burden. The burden normally applied has also little load for these.

Regular CT's like 200-5 types I heard making vibrating noise, but I also used them never on wires, carrying more than 20 Amps. Most of these have a warning sticker, saying NOT to open, but to short if no burden is applied.

Again these are home type CT's. To be safe, follow the instructions on the CT.

Can you provide brand name and nameplate details of those CTs?.

These CT's come with kWh meters and smart systems.

They have no nameplates on it, just loose end connections. The TED's are sold separately and also EKM metering CT's. The feed through holes are somewhat limited to around 25 mm diameter. If you like I can take some pictures. Details you will find on the EKM metering site.

GA!

Most low VA ct and standard precision have a low magnetizing inductance that prevents destructive voltage levels. They can still produce shocking levels.

But, large, high precision CT will produce much higher voltages. Beware of those...

An open CT will also produce some voltage drop and distortion in the line but it is often negligible.

I think equipment will stop working that is fed by C.T.

Funny, but true

AH, a current transformer is a current transformer. It takes emphasizing, that by design it transform current. The primary is a conductor passing thru (a single turn), the secondary is multiple turns. The turn ratio establishes the main ratio for it. Example: 1000 turn secondary = 1/1000th of the main current out of the meter. Normally, these coils come with a built-in load. That converts the current to a voltage to be displayed by a common voltmeter, and read as current.

But, what happens, when the load is missing? The transformer - forced by the magnetic flux - forces current thru its nonexisting load.

What do you call that? I call it arcing and short circuit along the line. That allows the current to flow.

That is why you never ever use a current transformer without a definite load.

If you say you do, it tells us plenty about competency.

Do you have examples of CT's with normally built in load?

well said ,to prove your point I had personally come across 2 persons with burnt hands and fingers. My curiosity proved that both are people involved in the private management of power who always deal hands on with CTs.

Maybe they need a new approach: "Look Ma, no hands!"

This is about everything to know about CT's

http://powermetrix.com/wordpress/wp-content/uploads/2013/01/GLEMS%202012%20-%20Inst%20Xformers%20Theory%20and%20Testing.pdf

DVM. I do not care about the details. You are welcome to them. You intend to disprove this and Newtons? You are free to try.

Will you accomplish any of that? Can try. But succeding, it depends my and your stupidity. Today, it is unlikely. In the future, the chesebrains make unlikely making coherent decisions.

You really ought to cunsult your textbooks about this and the herm relay otherwise you are unlikely to understand enough to pass your exams.

The magnetic circuit of the CT is made and once you start passing current through the cable it is monitoring then something must happen.

Amps Ohms and Volts are all tied together but in this instance you have an open circuit so no Ohms. Like the earlier contributors have said this will cause the voltage to go very high - possibly high enough to destroy the CT and possibly high enough to cause danger through electrocution.

It is usual to put a shorting link across a CT to prevent this happening. The shorting link will protect rather than damage the CT. Never put fuses in the CT circuit.