Best CT connected energy meter rating for a CT with secondary 5A

AI Thread Summary
The discussion centers on selecting the appropriate energy meter rating for a current transformer (CT) with a secondary rating of 5A. The supplier recommends a 5A(20A) meter, asserting it as the standard for 5A CTs, while the user believes a 1A(6A) meter would be a better fit for the current range of 5A CTs. Participants seek clarification on the standard ratings and relevant literature to support their decision. The conversation also touches on the importance of understanding the internal burden resistors in CTs and how they relate to the energy meters. Ultimately, the user aims to determine the most suitable meter rating for accurate energy monitoring.
tolerl
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I work in a Maldivian Utility Company. Our engineering team is pretty weak so I don't have anybody in the company to ask even though this is the state electric company.
A supplier quoted us 2 CT meters . Rating for one is given as 1A(6A) and other as 5A(20A) which I believe is 1A basic current Ib and 6A Max current and in other case 5A basic current Ib and 20A Max current.
Supplier is recommending 5A(20A) saying that 5A Ib meters is the standard approach for the 5A CTs and 1A Ib is for CTs with 1A secondary current.
But my understanding is 1A(6A) meters fit better with current range of 5A CTs.
I would like to clarify what is the standard rating for 5A CTs and point me to is any literature to get more information about matching meter rating with CT secondary rating.
Sorry for the bad English.
 
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tolerl said:
I work in a Maldivian Utility Company. Our engineering team is pretty weak so I don't have anybody in the company to ask even though this is the state electric company.
A supplier quoted us 2 CT meters . Rating for one is given as 1A(6A) and other as 5A(20A) which I believe is 1A basic current Ib and 6A Max current and in other case 5A basic current Ib and 20A Max current.
Supplier is recommending 5A(20A) saying that 5A Ib meters is the standard approach for the 5A CTs and 1A Ib is for CTs with 1A secondary current.
But my understanding is 1A(6A) meters fit better with current range of 5A CTs.
I would like to clarify what is the standard rating for 5A CTs and point me to is any literature to get more information about matching meter rating with CT secondary rating.
Sorry for the bad English.
Welcome to PhysicsForums. :smile:

I'm not familiar with that dual current rating, but I'm no expert on CTs either. I use 5A CTs with internal burden resistors in my current metrology work, similar to this one:

https://shop.dentinstruments.com/products/revenue-grade-hinged-split-core-current-transformers

1604169116820.png


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The internal burden resistor assumes that your CT input circuit has a Zin > 10kOhm or so (check the CT datasheet), and a max input Vrms of 333.3mVrms.

Can you say why a utility company is interested in monitoring 5A circuits? And what is your monitoring device? Does it assume that the burden resistor is in the CT, or does it have one of its own built into the input circuit?
 
CTs are class 1 measuring CTs. I want know what will be the recommended meter rating for these CTs.
 
tolerl said:
CTs are class 1 measuring CTs. I want know what will be the recommended meter rating for these CTs.
Can you post a link to the different classes of CTs? I'll try using Google in parallel. I'm only familiar with revenue grade CTs, and I'm not sure what "class" they are rated at. Off to Google...

Also, how does the CT that I posted above compare to your requirements?
 
It have one of its own built into the input circuit. I'm actually interested in recommended rating of the energy meter. Not the CTs. CTs are always class 1 measuring CTs.
 
tolerl said:
It have one of its own built into the input circuit. I'm actually interested in recommended rating of the energy meter. Not the CTs. CTs are always class 1 measuring CTs.
Can you provide a link to the CT datasheet please? Thanks.

What do you mean by "energy meter"? A DVM reading the Vrms output of the CT, or an automated analog Vrms to USB interface, or some other data aquisition system? What computer will you be wanting to read these CT data from? What computer interface (programming language, device interface, etc.) will you be wanting to use?
 
berkeman said:
Can you provide a link to the CT datasheet please? Thanks.

What do you mean by "energy meter"? A DVM reading the Vrms output of the CT, or an automated analog Vrms to USB interface, or some other data aquisition system? What computer will you be wanting to read these CT data from? What computer interface (programming language, device interface, etc.) will you be wanting to use?

https://www.edmi-meters.com/product/meters/electricity-metering-devices/mk10a/
This meter will read the data from CTs. These meter comes with either 1A(6A) or 5A(20A). I want know how to choose which rating is better since supplier is telling me 5A(20A) is recommended but my understanding is 1A(6A).

CT will something like this. https://new.abb.com/products/1SVR450116R5400/cm-ct-200-5-current-transformer-5va-class-1
 

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