Drill tripping earth leakage protector - Page 3

Have you actually measured the leakage current seen by the RCD? If so what
is it? If not, then how can you know it is not too high and causing
problems. Also you need to isolate the neutral at the MEN point, and
megger the neutral as well.

David

No.


You think the leakage current was regularly too high
at 7.30am and 10pm but OK at all other times and has
now stopped being too high at those times too?

Mike Harding

If the leakage current was marginal, then the added effect of the control
tones could be sufficient to trip the RCD, especially if the leakage was
partially caused by capacitance. Also, you mains voltage may have changed,
which changed you leakage a bit.

David

If that were the case I would expect random nuisance
tripping - there has not been any?

Any more suggestions?

Mike Harding

I suggest that you actually measure the leakage. If you can't do that, get
a electrician with the right gear to measure it for you. If you don't know
the standing leakage, you don't have any idea of how close the RCD is to
tripping.

David

"David"



**  No need to measure the standing leakage  - it is far easier to measure
the available margin before tripping of a protected circuit.  Just add some
known leakage current to earth at an AC outlet.

 Eg

 A 10 kohm, resistor draws 24 mA from a 240 volt outlet.

 Two of them in series draws 12 mA.

 Get the idea ??


 BTW  All appliances that are normally left on should be on for this test.



............    Phil

This is not the correct way to test for leakage, and you will have no idea
of what the leakage is for several reasons.

1) You don't know what current the RCD trips at. 30mA is a nominal
current, and the standard says it should not trip at less than 50% of
rated current, so it could trip anywhere between 15 and 30mA.

2) RCDs have a tripping time range, where the higher the current, the
faster the trip. AS3190 says that 30mA RCDs should trip at rated value in
less than 300mS. Lower currents will trip in longer periods. Unless you
time the trip operation (as required by proper testing) you won't have
much of an idea.

3) If the leakage is caused by capactitance, adding resistance will also
not give a true indication of leakage, as the currents are out of phase.

4) You still have no idea of the leakage current on the neutral, and its
contribution to the total leakage.

David

On Tue, 10 May 2005 09:15:03 GMT, Andrew



Oh that's just Phyllis - she's having a period or something,
as usual :)

Nevertheless - Phyllis may be (is!) a total social misfit but
does know a bit about electronics and what he says is
correct. Although I do agree, increasing the leakage with
resistors is a bit of rough method and won't tell you what
the current (no pun :) leakage is to much better than 50%

But I must say you are still a very long way away from
convincing me that the tripping of my breaker was not due
to the tones.

Mike Harding

David if the earth leakage in my house was running close
to the 30mA trip rating of my breaker then I would see
nuisance tripping, especially, over a long time period.
That has not happened - once! - however, as I stated,
there was a contiguous time period when the breaker
was routinely tripping at 7.30am and 10pm.

Mike Harding

finger to keyboard and composed:



I wonder if the following arrangement could be used to measure the
leakage current in a particular appliance. The leakage would be
mirrored in the single-turn secondary winding and displayed directly
on the ammeter. Otherwise one could use a multiple turn secondary and
a more sensitive ammeter. I suppose one could dissect an ELCB and
adapt it for this purpose.

       toroid
         _             __________
        / \           |          | -> Ileakage
 A o---/---\-----o o--|appliance |_____
 N o---|---|-----o o--|          |     |
     __\___/__        |__________|     |
     |  \_/  |                        _|_
     |       |                         =
     |       A   ammeter               E
     |_______|
        ->
      Ileakage


- Franc Zabkar

Yes, that would work, assuming the torroid was OK. The recommended way to
test for leakage is to use a sensitive tong ammeter. You can get ones that
have 40mA FSD, and you basically clip them over the active and neutral and
measure the total leakage current directly.

David

Could it possibly be an off peak device like hot water heater?

Bryan

"Bazil"




**  Electric water heaters usually have their own circuit, separate from the
RCD protected power outlets.

 Like electric stoves, heaters are known to have fairly high leakage
currents.




..........   Phil

How do you think the ripple frequency gets to the relay?, from its own
separate circuit?
Yeah right!

the

On Wed, 27 Apr 2005 09:55:21 GMT, Glenn Pure
and composed:



How accurately can one match the A and N windings in the ELCB's
toroid? Let's assume that there is a 1mA balance error, at rated
output, due to manufacturing tolerances. When a high power device is
switched on, the inrush current may be ten times the normal operating
current, or even greater. Under these conditions, wouldn't the error
be magnified in the same proportion? For example, a 30x inrush may
result in an effective 30mA imbalance which would be enough to trip
the ELCB. Does your problem persist if you defeat the earth pin?


- Franc Zabkar

"Franc Zabkar"



**  A home drill press will never even approach creating a 300 amp surge  -
my 1/4 hp one barely makes a 3 amp one. In any case -  a 300 amp peak surge,
of only one half cycle duration, will trip a domestic 20 amp breaker every
time.

In my home workshop, I have a 20 amp breaker and a portable RCD in line from
the AC outlet.  The worst surges are from large ( ie  1 kVA ) toroidal power
transformers and will regularly trip the breaker but not the RCD.




.............    Phil

I had a drill press that was doing the same thing. I tried using the
drill plugged into an ELCB built into a power board (one of the HPM
ones), and it still then tripped occasionally but only the board,
instead of the house one tripping. Worth a shot if you can't find a
better solution.

I'd say it was luck that the power board was probably a little quicker
than the house, and it only happened on switch on, I suspect some
relationship to the inrush current, and the voltage phase as I hit the
switch.

The drill is now out in a shed, with an ELCB, thaty doesn't trip at
all.

- Rob.

Thanks for this, and all the other advice.

I had already thought of your fix, Rob and will go that way if I have
to.

Cheers
Glenn

snipped-for-privacy@r.r.com wrote:



                                Glenn Pure
                       Canberra, Australia
Web page: http://www.evans-pure.net