I need to build a circuit which can detect current in water

[shaz]

Prevent current in water

Hi friends,

I'm having a small boiler in which i'm boiling water with a electric heater(220v AC, 2000W). Now, my problem is after using it for few months the heating element bursts out and there is electric current in water and pipelines. I want a circuit which can detect current in water. There is one additional problem, The phase and neutral line may get inter-changed.

Any help would be appreciated.

 

[IanP]

Re: Prevent current in water

If this system is earthed then a Residual Current Device (RCD) will trip as soon as there is a current leakage from Active-Neutral loop --> to Earth .. so, the sequence of Active - Neutral doesn't matter ..

If you can isolate this system from Earth then you can implement so called "Ground Isolation Monitor" concept, which basically is an 1:1 isolation transformer (Active - Neutral sequence not relevant), adding a very low current DC voltage, say 100V, and a circuit that senses this DC voltage ..
This option allows you to "monitor" (measure) the impedance (resistamce) between the isolated circuit and EARTH, and if a fault occures switch the voltage OFF within ≈25ms (with a solid state relay) ..

Regards,
IanP

 

[shaz]

Prevent current in water

First of all i should say i'm thankful to you, for the efforts u took to reply me. Secondly, i feel sorry to say, the EARTH line is also not present. (i.e. only Phase(live) and neutral are present). what can i do in this case.

 

[IanP]

Re: Prevent current in water

You can create EARTH locally by bearing (or hammering) a copper rod (according to your local standards, my guess is that it should be at least 1m long @ Φ>10mm) or other option, and very common practice, is to use the nearest water tap as the local EARTH reference ..
Regards,
IanP

 

[shaz]

Prevent current in water

Thanks for taking the efforts again. Idea is good for making the Earth connection. Please check this link, **broken link removed** , will this work?. If you think this won't help much then please explain more of the hardware part which you were suggesting.

 

[IanP]

Re: Prevent current in water

RCD (residual current device) = G.F.C.I (in USA and Canada)

An RCD will help to protect against electric shock where current flows through a person from a phase (live / line / hot) to earth. It cannot protect against electric shock where current flows through a person from phase to neutral or phase to phase, for example where a finger touches both live and neutral contacts in a light fitting. It is virtually impossible to provide electrical protection against such shocks as there is no way for a device to differentiate between current flow causing an electrical shock to a person and normal current flow through an appliance. Protection against electrical shock of this nature must be through mechanical means (guards or covers to protect against accidental contact) and procedure (e.g. switching off power before undertaking maintenance).

Quoted from: https://en.wikipedia.org/wiki/Residual-current_device

As I mentioned before, this device "will trip only if a fault occurs such that current flows to a true ground", so with "true ground"=EARTH it will work (with limitations stated above) ..

Regards,
IanP

 

[garg29]

Re: Prevent current in water

thnx again .my main problem was to detect whether there is current present in water or not.person getting a shock is a secondary issue.

can i detect electric current in water before a person touches it.

i think i m getting away frm the main problem

please help me out sorry for disturbing u again and again

 

[IanP]

Re: Prevent current in water

To detect "current" in water you can try to implement a "Touch Circuit" with its electrode in water (the other electrode can be connected to EARTH) ..
The sensitivity of this circuit has to be adjusted in experimental way ..
Here is an example:
**broken link removed**
Regards,
IanP