Earth current

[Streetwear87]

Hi Everyone!
We build a 3 phase electric grill at my company.The grill has 6 elements.The elements are connected in delta, but..
4 elements work with a thermostat and 2 element work with an energy regulator.
So thermostat 4 elements connected:
L1-L2
L1-L3
L1-L2
L1-L3
Energy regulator 2 elements connected:
L2-L3
L3-L2
Also we have 3 led.Every phase have 1 led.
Phase 1 has the all 6 mini fan.
My problem is,i found 1 ampere on earth.If only energy regulator works with the 2 elements,no current flow to earth.Immediately i turn on the thermostat(4 elements) 1 ampere current flow to earth.
There is a 4 pole RCD what does not trip in this situation neither.
Neutral connected only to led and to fans.
There is no cross connection and the insulation resistances are all fine.
RCD disconnection time is fine and test button as well works.
My question is, how possible there is 1 amp on earth?
Why RCD does not trip?
Why i do not get electric shock if i touch the exposed metal part of the grill?

Thanks!!

 

[pc1966]

How are you measuring this?

A diagrem might help explain how things are connected a bit better!

 

[Streetwear87]

Wi

How are you measuring this?

A diagrem might help explain how things are connected a bit better!

How are you measuring this?

A diagrem might help explain how things are connected a bit better!

With an earth clmap.
From main switch the 3 phase fo parrallel to the thermostat and to the energy regulator.
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Wi

With an earth clmap.
From main switch the 3 phase fo parrallel to the thermostat and to the energy regulator.

Both can work separately.

 

[davesparks]

You should measure earth leakage by clamping a suitable low reading meter around all live coductors, so 3 lines and neutral in this case, and taking a measurement.

This measures and imbalance and thus the total leakage from the circuit.
The actual leakage is often different to the current measured in a protective conductor.

 

[Streetwear87]

You should measure earth leakage by clamping a suitable low reading meter around all live coductors, so 3 lines and neutral in this case, and taking a measurement.

This measures and imbalance and thus the total leakage from the circuit.
The actual leakage is often different to the current measured in a protective conductor.

Thank you very much!!

 

[plugsandsparks]

How big are these elements compared to your incoming supply. From your config, when the thermostat brings in the 4 elements its un-balanced and as such will create a neutral current. Typically L1 is a favourite phase anyway so you may have a very large neutral current caused by a large load on L1 compared to L2 or L3 at site level.Then it comes down to the type of earth system in place, i.e. TNCS where the N conductor is actually the earth. You may find that your grill has a better earth in the building than the return path of N back to the supply grid, hence you are seeing other Neutral currents coming your way.
Anyway i see large earth currents all the time in industrial and commercial settings. The RCD is monitoring the actual load so if its happy, then hopefully this will allay any fears.
You wont get a shock off the appliance but if you disconnect the earth and put yourself between the earth and the appliance you may well get a right old belt (dont try it)

 

[Streetwear87]

How big are these elements compared to your incoming supply. From your config, when the thermostat brings in the 4 elements its un-balanced and as such will create a neutral current. Typically L1 is a favourite phase anyway so you may have a very large neutral current caused by a large load on L1 compared to L2 or L3 at site level.Then it comes down to the type of earth system in place, i.e. TNCS where the N conductor is actually the earth. You may find that your grill has a better earth in the building than the return path of N back to the supply grid, hence you are seeing other Neutral currents coming your way.
Anyway i see large earth currents all the time in industrial and commercial settings. The RCD is monitoring the actual load so if its happy, then hopefully this will allay any fears.
You wont get a shock off the appliance but if you disconnect the earth and put yourself between the earth and the appliance you may well get a right old belt (dont try it)

Thank you very much!

 

[Streetwear87]

I have checked phases and neutral with earth clamp, but i have the same amount, 1 amp around.We built another grill but there is no current on the earth.Everything the same between these grills.Parts,elements,system etc..

 

[pc1966]

Are you sure you are clamping all feed conductors? If it is an intermediate point you are measuring you might be missing one path (e.g. if live to control box is taken before and neutral returned after).
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Also how does the "Energy regulator" you mentioned work? Is it some sort of high frequency switching regulator or similar? I'm wondering if there is some very unusual waveform that is upsetting your clamp meter.

 

[Streetwear87]

Yeah,i was clamping all feed conductord at the main switch.

 

[Streetwear87]

I checked the leds.All 3 leds have one phase and neutral connection,because it works on 230V.Every leds have 30 mA leakage.

 

[Streetwear87]

I mean i am sure there is leakage from the elements but why RCD does not trip....
Sorry guys but my brain is ready to explode

 

[pc1966]

Yeah,i was clamping all feed conductors at the main switch.

Is that the main switch of the equipment (i.e. internal) os part of some external test feed you are using?

If internal then can you repeat it on the actual feed cable where it is separate enough to clamp the phases+N but exclude the CPC?

 

[Streetwear87]

It is internal yes.800 mA around.a bit less but still a lot

 

[pc1966]

It is internal yes.800 mA around.a bit less but still a lot

Is that the clamped value externally to the equipment (e.g. on feed cable away from it)?

If you clamp the CPC separately what do you get?

 

[Streetwear87]

Red in this case is neutral.I do not understand your question.So i share a picture.I clamped at both place(like on picture)
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At first picture is 1 amp.at second more far from earth conductor is around 800 mA