# Earth leakage Detection "positive" as well as "Negative" >30mA.

1. ## Earth leakage Detection "positive" as well as "Negative" >30mA.

Hi ,
I am working on one project in which it require earth leakage detection >30mA on both positive and negative side.
So,could you please suggest me proper reference books or articles and methods to implement it, because I am unaware of it.
Thank you

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2. ## Re: Earth leakage Detection "positive" as well as "Negative" >30mA.

Hi,

The only useful informations is "30mA"

With "earth leakage" I think about AC ... which is alternating. And the value usually is given as amperes RMS.

But then you emphase that you want it to be positive and negative. Maybe you want to detect DC currents?

Why not use a simple amperemeter?
Did you look for RCD circuits and how they work?

How should it work? At a (disconnected) earth line in a house? Or across two metal poles rammend into the earth?

And what does "detect" mean?
Glowing a LED? Showing it on a 7 segment display? Or as waveform on a scope? Or transmitted via internet to your computer?

It could be anything. It could be simple ... or very difficult. Depending on what you really need.

Klaus

3. ## Re: Earth leakage Detection "positive" as well as "Negative" >30mA.

Ordinary multimeters like I've used detect current as DC only.
Here's a handy trick to measure AC current: Insert a resistor inline, and measure AC voltage across it. Resistor value should be very low ohms, enough to obtain usable voltage readings. Divide volts by ohms.

4. ## Re: Earth leakage Detection "positive" as well as "Negative" >30mA.

you set up a balanced 30mA using a class B amp structure with the earth in the middle - that way if either the + or - is pulled to earth by more than 30mA a resistor volt drop can be used to drive an opto indicating earth leakage.

the other way is per the standard earth fault breaker technique, send and return wires on a CM toroid with a gap for a hall effect device, more than 30mA diff = > "x" B field which is detected on the hall effect ....

5. ## Re: Earth leakage Detection "positive" as well as "Negative" >30mA.

here you go :-

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6. ## Re: Earth leakage Detection "positive" as well as "Negative" >30mA.

Hi ,Thank you very much I will try this and let you know the status .
Thank you

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