Fault on RCD Trip

[batty]

Has the Rcd tripped any other time when lawn mower is not going?

 

[a1]

Thank You for the Update Kenwood.

Maybe you could get an Electrician from our foum here, to come and have a look and to do some testing?

Please keep us informed. We are genuinely interested and hope that you can get it sorted to your satisfaction.

Sidewinder - That would be great if you can, Mate. - Thank You.

Best Regards,

Admin.

 

[davetheglitz]

Don't know how I've missed this post - some interesting points!Not sure if this approach has been covered - and it's something I have a hard job to wrap my brain around - but I reckon it's all down to transients.

As far as I can see these faults always seem to be associated with motors. As these are brush type motors I can imagine that current is being interrupted at the commutator resulting in some high frequency transient voltages - much like an ignition system on a car (points = commutator, coil = motor windings).

Assuming the motor is double insulated and there is no earth fault, then the neighbours RCD may have an instantaneous difference in current between live and neutral (storage via the motor winding inductance?) - but over a cycle it may even out - i.e. fault not there long enough to trip the RCD - and symmetrical.

As the earthing is PME it is possible that some of the transient may find it's way through the RCD coils to appear on the Line and Neutral.

At the OP's house neutral terminal the transient now has two paths to an appliance. One via the neutral winding of the RCD - the other via the cpc. The transient on the neutral would be attenuated due to the induction of the winding. However the transient at the CPC - assuming a high impedance path to either live or neutral via cable capacitance or appliance resistance - would not be attenuated, and would also be phase shifted to the neutral current due to the induction. So now there is a possibility of a differential and non symmetrical current existing - maybe enough to trip the RCD.

Am I barking up the wrong tree here?

Perhaps it's worth checking if the strimmer suppressor capacitor is fitted- or whether there is any radio interference from it?

Added a diagram in the hope that someone can check out the theory. It sort of makes sense on paper - but can't put any figures on it for the real world.

Cheers

Dave

 

[kenwood33]

I should have mentioned it was 0.32 and not 3.2 as I previously mentioned so apologies for that. I got my figures wrong. The only thing that causes the fault is the strimmer, we have narrowed it down this morning by switching off various appliances and finally it was the strimmer and not the lawn mower. Any more ideas would be welcome as it seems we might need a new RCD in our consumer board at the end of all this.

 

[batty]

So it has only ever tripped when strimmer is on?

 

[m4tty]

Has the strimmer been tested (pat tested)?

 

[Theorysparky]

try the strimmer on the ops cu......if it trips then it maybe the ops rcd

BUY THE GUY A NEW STRIMMER !!!!!!!!!

 

[steptoe]

Dave, a good drawing,

Im still not at the level do do stuff like that yet,

and I agree it is very possible,

but also to the possibility of the spikes being picked up via the OPs spike(PME alledgedly) and therefore also unbalancing the trip.

could also be a leaking extension lead.

this would be further fed by the fact it is the strimmer, (this also supports your theory no end) and not the mower, the strimmer is stop start (your spikes again), where as the mower is more continuous.

 

[green-hornet]

0.32 on a pme(sorry steps) I know. is already high and given daily fluctuations would suggest an end of line TNC-S installation.

I have found these to be very unstable over the years, to such an extent that I published a paper written to the NICEIC in 2005 about variations in supply on PME.

I am totally convinced that variables in the supply network are not very reassuring, which is why I have always advocated the use of TT installations.

I normally avoid arguments against this view, simply because many people do not understand PME or TNC or TNC-S installations and the appropriate problems with each.

 

[thomas123]

Sorry to dig up an old thread but what if your neighbour has tapped off your electric? do you live in a terraced house with no dividing walls in between the attics?