[SOLVED] Measuring leakage current of mains using Current transformer

[Mrunal Ahirrao]

Hello everyone,
I am trying to measure leakage current using current transformer.I am using this circuit **broken link removed**
And instead of LM324 I am using OP07. But when I try to leak current the transformer don't respond to any leakage. maybe my leaking curent method is wrong. Experts please guide. I am attaching detailed schematic of my method.

 

[FvM]

OP07 needs dual power supply. Do you have it?

 

[Mrunal Ahirrao]

yes I have used dual power supply

 

[erikl]

View attachment 115162

If your Neutral is also very well earthed, you don't get a difference current by this method, just an additional load current.

 

[FvM]

If your Neutral is also very well earthed, you don't get a difference current by this method, just an additional load current.

If the "leakage" resistor is connected between earth ground and phase, as indicated in the schematic, it will generate about 23 mA residual current with 230 V mains voltage which should be well detectable with a correctly designed sense amplifier.

 

[chuckey]

For a better test, connect your 10K to the incoming neutral and not "the wall". If its a well insulated wall then the leakage current could be microamps.
Frank

 

[Mrunal Ahirrao]

For a better test, connect your 10K to the incoming neutral and not "the wall". If its a well insulated wall then the leakage current could be microamps.
Frank

Hi frank,
If I connect in that way then, that cannot be called leakage current as the current would go to neutral which won't make any inbalance in currents.

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If the "leakage" resistor is connected between earth ground and phase, as indicated in the schematic, it will generate about 23 mA residual current with 230 V mains voltage which should be well detectable with a correctly designed sense amplifier.

Yes but there is no output from amplifier. And the circuit I have attached link of is good? I have set it for gain of 100

- - - Updated - - -

If your Neutral is also very well earthed, you don't get a difference current by this method, just an additional load current.

So how should I leak current?

 

[FvM]

If I connect in that way then, that cannot be called leakage current as the current would go to neutral which won't make any inbalance in currents.

Review the test circuit of an industry standard RCD device, it's usually printed on the case. The resistor is connected between phase (after the CT) and N (before the CT), or as Frank said "incoming neutral", so it generates a perfect test current.

Yes but there is no output from amplifier. And the circuit I have attached link of is good? I have set it for gain of 100

Lack of information. What's the shunt resistor value? Which CT type, is it high permeability CT core? Number of secondary turns? If all parameters are correct, there can be still a circuit fault,

It should be also no problem to check the sensor with higher AC currents.

 

[Mrunal Ahirrao]

Review the test circuit of an industry standard RCD device, it's usually printed on the case. The resistor is connected between phase (after the CT) and N (before the CT), or as Frank said "incoming neutral", so it generates a perfect test current.


Lack of information. What's the shunt resistor value? Which CT type, is it high permeability CT core? Number of secondary turns? If all parameters are correct, there can be still a circuit fault,

It should be also no problem to check the sensor with higher AC currents.

Burden resistor is 10 ohms and CT type is unknown but its high sensitive with 7ma minimum with 525 secondary turns. And I have checked it to measure current in usual way and its working. But not when sensing leakage current.

 

[Mrunal Ahirrao]

I have tried putting the resistor terminal(that I am touching to Wall) to direct Earth and now I am seeing some "voltage" at the output of amplifier but its too low. As frank suggested it maybe microamps. Now I will change the amplifier gain to 500 an see again.