How to make a CT detect current flowing along a conductor in 1 direction only. So if the CT were clamped on the conductor reverse, or the conductor current flows the other way then no current will flow in CT output to sensor?
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\$\begingroup\$ You don't block the current, rather you clamp the voltage. \$\endgroup\$– D.A.S.Commented Mar 30, 2017 at 0:59
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2 Answers
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You can't.
How is the current transformer supposed to know which way is which? It has no way of telling the difference between current flowing the "wrong way" and being clamped onto the wire backwards from how you expected.
You can certainly ignore readings below zero in your measurement device, or possibly even clamp the reverse voltage with a diode. But there's no way to figure out which direction is which without some other source of information.
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\$\begingroup\$ Thxs so far guys, however if you look at the diagram here: fccid.io/document.php?id=923083 this is the actual circuit of the device I want to detect the current direction flow at one of the CT in top left. How to modify the CT circuit? \$\endgroup\$– YackiedaCommented Mar 31, 2017 at 0:50
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You absolutely can tell which direction the current is flowing with a CT.
You need to measure the phase relationship of the voltage on the wire and the current waveform (a voltage output on the burden) from the CT.
If the signals are in (even mostly, allowing for power factor) phase then power is flowing in one direction, and if they are out of phase (even mostly) it's flowing in the reverse direction.
This might help you.
answered Mar 30, 2017 at 5:56
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\$\begingroup\$ Thxs so far guys, however if you look at the diagram here: fccid.io/document.php?id=923083 this is the actual circuit of the device I want to detect the current direction flow at one of the CT in top left. How to modify the CT circuit? \$\endgroup\$– YackiedaCommented Mar 31, 2017 at 0:45
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\$\begingroup\$ Since the CT's plug in using connectors it would seem possible to unplug the CT and pre-process the CT output using some external electronics. If the current flow is forward, enable the CT signal into the unit, and if it's in reverse turn off the signal. \$\endgroup\$ Commented Mar 31, 2017 at 5:18