Measuring leakage current in 3-phase system with current transformer

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#1
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Hi, I want to measure a precise number of leakage current in the 3-phase trace heating system.
The problem I faced is that typical current transformer gives a very high error at small currents. I found some solution either to use larger core or to apply some active compensation to pre-magnetize core. 
I think it is easier to pre-magnetize core because I have tight space requirements for the device, so larger core simply will not fit.
But I can't find information about pre-magnetization. The only thing I know is I need to apply the voltage with same or 3 times frequency.
In some industrial device, that does the same function I found two secondary windings, obviously one for pre-magnetization and one for measurement.

Can somebody help me with this questions:

1) What type of waveform do I need to apply to additional secondary winding?
2) What parameters of additional secondary winding
3) Can I use same core?

Alexander

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You'll have to fight the magnetic field hysteresis somehow.

 

You might want to buy a uni-t  ut210e.

This is a hand held current clamp meter (usd 30 from Al / Ebay) with 3 ranges.

The lowest range is a 2A range ( AC and DC) and has a resolution of 1mA.

DC range seems a bit shakey on the lower mA measurements but that was to be expected.

 

There are quite some unboxing / teardown video's on youtube about this meter

https://www.youtube.com/results?...

 

Anyway,

you can reverse engineer this meter a bit and if you don't demolish it you will have a quite usable clamp meter afterwards.

 

 

 

 

 

Paul van der Hoeven.
Bunch of old projects with AVR's:
http://www.hoevendesign.com

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Hello Gordon, I manufacture a product for that specific application. Do you need just one or many? Send a pm if interested

Tom Pappano
Tulsa, Oklahoma

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Hello Tpappano

 

I am interesting in devices for leakage current measurement. Especially for street lighting lines.

Can You propose some of Your products or solutions.

 

Please sent info in my E-mail.

 

Best regards,

Petras

PETRAS

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Hello Petras,

If you will send me a "private message" with your contact info, we should be able to work something out.

Thanks!

Tom Pappano
Tulsa, Oklahoma

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Hello Tpappano,

 

I don't have Your personal E-mail.

Please write me in   ...... * email address removed to protect you from extra spam. *

 

BR

Petras

PETRAS

Last Edited: Sat. Aug 12, 2017 - 10:52 AM
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Petras.

 

This website has a "private message" facility. If you click on blue coloured username located above the avatar position on the left side of his post, you will be taken to a page that includes a hotspot named "Send private message". Click that and then write your message. Tom will get it and then you two can commence dancing.

 

Or... just click on the "Send PM" button below Tom's avatar.

 

Cheers,

 

Ross

 

Ross McKenzie ValuSoft Melbourne Australia

Last Edited: Sat. Aug 12, 2017 - 10:55 AM