Earth leakage current

[Dambo]

What would cause high earth leakage current?

 

[ianmacd]

Care to be more specific as it could be amythings either by design or failing.

 

[Dambo]

I've heard instances where high earth leakage current has caused RCDs to nuisance trip. I was just wondering what would cause this to occur? How to measure the exact reading? And how to overcome it i.e. stop RCD nuisance tripping?

 

[ianmacd]

Computers tend to be one of the worst offenders for this these days. The only way to stop nuisance tripping on the RCD is to move the circuits over more RCD's and possibly split circuits too.

 

[spinlondon]

Computers and heating elements, such as found in cookers, washing machines, dishwashers and storage heaters.

 

[ian932]

Class I equipment with switch modes PSU's and filters, High frequency lighting.

 

[paul b b]

Computers and heating elements, such as found in cookers, washing machines, dishwashers and storage heaters.

+1

also fridge & freezers

 

[Dambo]

What causes the earth leakage though i.e why are these the worst offenders?

And how can the exact earth leakage current be measured?

 

[Dean182]

Earth leakage current is the current that normally flows in the earth conductor. It's the difference in the current between phase and neutral. It's caused when either conductor is raised to potenial greater than the earth the amount depends on voltage, resistance between conductors etc. It can me measured with an earth leakage tester. Like a clamp meter.

 

[Andy™]

often cause my dampness or breakdown of insulation between conductors.

or in some cases (computers), the filters leak some current to earth

 

[netblindpaul]

[quote name='Andy

 

[PBC_1966]

In many power supplies for electronics the leakage is a consequence of the capacitors used for filtering. For example, a 0.1uF capacitor will have an impedance of about 159 ohms at 10kHz, and less at higher frequencies as capacitive reactance varies inversely with frequency.

But even though by the time you get down to 50Hz the impedance will be relatively high, it will still allow for some appreciable leakage current to flow, e.g.that same 0.1uF capacitor will be about 32k impedance at 50Hz, allowing a leakage current of approx. 7.5mA to flow.

 

[markysparky]

Am i right in saying you measure current by testing in series, voltage in parralllel across supply. You can disconnect the earth to the circuit and test with a multimeter on mamps setting, from the met to the cpc of the circuit. This would show the milli amps flowing in the cpc. ?

 

[Lurch]

Am i right in saying you measure current by testing in series, voltage in parralllel across supply. You can disconnect the earth to the circuit and test with a multimeter on mamps setting, from the met to the cpc of the circuit. This would show the milli amps flowing in the cpc. ?

That it would.