Field Measuring High DC Current

[catserveng]

I am trying to do some field troubleshooting on a large DC drive system at 600 VDC and rated at 3200 amps.

I am trying to find a field installed current sensor for DC current that is fast enough to get transient type information. Google search so far hasn't gotten me much help except for a 6000 amp Hall effect from ChenYang.

Installing a shunt would be very difficult in this application, was hoping for a flexible type CT to use with a scope or power quality analyzer. A split core CT could also work, going around four 1000 MCM conductors.

Any suggestions appreciated, thanks

 

[davidbeach]

A CT wouldn't do much for you on DC currents. You need your Hall Effect Sensor or something else that can respond to DC.

 

[dpc]

You might check with these guys. We've used them for very high current (50 kA) dc sensors - but that was a permanent installation.

http://www.lem.com/

 

[slavag]

Hi Catserveng.
Please see attached

http://www.abb.com/product/seitp322...80034c11c.aspx?productLanguage=us&country=IL.

Hope it help.
Best Regards.
Slava

 

[ScottyUK]

LEM have some newish designs which reach out beyond the 10kA level with reasonable bandwidth. The LT series looks like a good bet:

http://web4.lem.com/hq/en/component/option,com_catalog/task,displayserie/serie,LT/output_type,/

One thing to be aware of with some LEM transducers:
If the conductor voltage varies significantly relative to earth, capacitive coupling between the conductor and the electronics can cause errors to appear in the output signal. The problem is worst with high dV/dt signals, but a controlled rectifier is plenty fast enough to cause peculiar effects to be seen in the output signal. We have frequently and successfully used a grounded copper foil on the inner face of the transducer to provide an electrostatic screen between the electronics and the conductor. I don't know if this affects all their products or just certain types but it can confuse the unwary.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[Skogsgurra]

You *may* get away with a simple Allegro analogue sensor. But make sure you don't have any other fields near that conductor.

And, please, do not count on any accuracy with regard to levels. But you can see pretty well what your waveform is doing. And rather high up in frequency, too. Count on placing the sensor several inches away from the cable so it doesn't saturate. Also, a copper foil with a ground strap is good to have between cable and sensor. Wrap round the cable (if it is insulated, of course!).

But, as I said, only for dynamic and relative measurements.

I have used a large Hall Effect device from LEM - it was made to measure and did cost some USD 2000+. That was about ten years ago. Maybe standard now - and cheaper.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[catserveng]

Thanks all for the replies. Slava, the ABB product looks interesting, hoping to hear back from the salesman tomorrow.

LEM had some product that looked like it may work, but lead times are very long right now. Trouble with the service business, customers want their problems fixed NOW!

Thanks again, Mike

 

[Generation]

Just a very simple basic suggestion: Maybe you can make use of the existing resistance accross one of the joints/connections, or even a part of the cable, in your DC powerline. Since any connection has some sort of a resistance, you will be able to detect a (low) dc voltage which is linear with the current. All you need to do than is to scale the signal and to read it with a recording scope or datalogger.