extension leads - earth leakage

[s harris]

Hi all,

I can't understand why but I always get a small (minimum 0.06mA) earth leakage reading on extension leads (even without surge protection).

Is this normal?

If it is, please could someone explain how earth leakage occurs on a simple extension lead?

Thanks

 

[James]

How are you measuring it?

if it is a long lead, there could be some inductive coupling between the cores as they are running parallel to each other

 

[Lucien Nunes]

This is likely capacitive leakage. For example, one metre cable with 30pF between line and earth conductors would have a capacitive reactance of 1/(2*pi*50*30Exp-12) = approx 100MΩ. At 230V a 25m cable will leak 25*230/1Exp8=0.058mA. This is a genuine current that leaks across all cables all the time they are energised but because it is reactive it doesn't register as power consumption on a watt-hour meter. It's also pretty small, and off the bottom of the scale of some testers; mine only displays <0.1mA when this low.

 

[s harris]

Ah super. Thank you both!

 

[i=p/u]

Are tutor taught us all that malarkey and all made sense at the time, as of today its pie to the power of 12 up in the sky..

Excellent that you so fluent.