20P5 Testing for CT

If the test procedure isn't documented, it is of no use at all.

Follow the applicable test procedure and you will be fine.

If you don't have the applicable test procedure, get it.

My dear, are you aware about you say ?

My question is how to check and confirm one CT's class.

IEC standard for CT testing is 60041. Even in the standrad it is only mentioned that accuracy limiting current should be found at rated frequency and rated burden of the CT. There is no description about, how to check or confirm the accuracy limiting current.

That is why asked how can I confirm the class of the CT.

Is it clear for you ?

http://www.success.com.my/content/download_success-ses.pdf

It is obvious that you do not know what you are doing or saying . . . so do not do it - as you may hurt yourself. I trust you are someone who has filed his EE exams and not working int he industry.

An IEC expression "20P5" does not exist. If it did exist - it would mean 20% error @ 5 times overload, . . . and not what you are saying.

What you are doing is most likely a home-work assignment. So - do your home-work first, . . . and decide if you want to do the actual test later.

I agree with you. I made a mistake. It should be "5P20" class. So how much time I can safely apply 20 times rated current ? Because I don't need to damage a good CT.

As you told, I don't know about it.. That is why I am asking. Otherwise my question will not be here.

I am working in the field of calibration more than 2 years. But I never done the test for CT.

No one in their right mind would apply 20 x rated current to any electrical equipment for 1 minute - as you suggest. Such a test will not only damage the equipment (CT) - but it will blow up in your face . . . Such overload test are typically done for 5-6 cycles (0.1 second) at the most, . . not seconds . . never minutes . . .

Also, no one would do such an overload test without first calculating the approximate performance of the equipment.

So, first measure the excitation characteristics and the winding resistance of the CT, . . . then calculate it s performance, . . . then decide if your really want to do the test. You will need some fine test equipment in order to the test and get the test data.

I suspect that you do not even know how to calculate the CT performance . . . . therefor you might want to buy, borrow or steal a "CTERP" from ELTEL Instruments (Bangalore) and have the "CTERP" provide the information for you.

thanks for your valuable advise. BUT WE DON'T NEED TO STEAL SOMETHING WHICH WE DON'T HAVE. MAY IT IS THE CULTURAL DIFFERENCE OF BOTH PLACE. Anyway I have Omicron VE000656 and Soken micro ohm meter. I have CT secondary winding resistance value, excitation curve, knee point voltage and maximum applicable voltage for excitation test. From these data how can I find whether it is according to 5P20 class ?

The guy must have a death wish.

Having seen a CT (100/5) explode under 10X load for 1 minute, I don't want to see it again. It was a test, but we weren't testing the CT, it failed before what we were expecting to fail.

It was in a safe zone, so no access.

"The guy must have a death wish"

I think you are out of common sense. Because in my question itself I mentioned that "it may be dangerous". That is why I asked. The intention of the question is to get a method to check 5P20 class and not to execute the wish.

As I understand your requirements, you are check testing an already manufactured protective CT to ensure that its errors comply with the nameplate rating for commissioning / application purposes.

You are not designing/manufacturing a "new CT" & you are not trying to determine the CT's short circuit withstand dynamic capability.

There are two types of composite error tests according to IEC60044-1, type test for "new CT" design & routine tests for an already type tested CT.

The indirect routine composit error test is detailed in clause 12.6 & by simply energising the secondary winding you can ascertain whether the composite error is within class 20P5.