Fault on RCD Trip

[a1]

is this a reason we should all put our actual location on our profile?I know mine isnt too specific either, Im on my way to changing that as I type.

It is one of the reasons that I have added the 'Location' section to the posts and to your profiles. It is also the reason I, from time to time, try and remind you all to update your profiles, especially with regard to your Location.

I am disappointed that this have not been done.

 

[Voltimax]

Lets hope he can persuade them to give it a look, and if they do that he lets us know if he gets a result.So were are You Dereham is it or Wymundham?

I'm in the Dereham suburb as I like to call it, Toftwood. Wymonham you mean? Pronounced Windham is a little further away

 

[Voltimax]

It is one of the reasons that I have added the 'Location' section to the posts and to your profiles. It is also the reason I, from time to time, try and remind you all to update your profiles, especially with regard to your Location.I am disappointed that this have not been done.

With all due respect Admin, there are some that may not want their location known.

It's like a Karate forum I belong to where they make you put your real name in your signature, if you don't comply, you get banned ?:|

 

[Sidewinder]

Steps,

Sorry for the delay in replying to your earlier 2 posts on my "quals" and my giving your suggestion a "heads up".

I have had some pc problems, needed to protect some data so all or our pc's have been off line.

In the words of a famous tv "engineer":

Ye cannae deny the laws of physics Captain.

Best said in a Scottish accent.

If the physics is right it is right, just because I have these qualifications and you do not, does not mean that you are wrong.

Please remember we have both been to University, it's just that i went to another one as well as the University of Life you attended.



ADS, Andy

 

[a1]

With all due respect Admin, there are some that may not want their location known.

Quite true Mate. And as a result I have just made it not compulsory. ** Note for all members ** You all have a choice now - if you want to have it, please complete your correct location - if you don't want leave it out. If it is not used for your location, I will delete them over time.

It's like a Karate forum I belong to where they make you put your real name in your signature, if you don't comply, you get banned ?:|

I wouldn't go that far.

 

[Riggy]

Steps,Steps has some forthright ideas on earthing.

I have no issue with Steps views on earthing, or the importation of a fault into an installation if there is an external PME fault.

I also fully understand your, more eloquent description on the same thing.

I can't argue either with Special Location's description of three phase generation.

All good stuff.

My problem (and without putting words in their mouths, I think ADS and Andy's also) is that I can't see how any of this would cause the OP's RCD to trip.

When I read your earlier posts, I got to the end of the second instalment, and expected a third, the punchline, which drew it all together and expressed your conclusion (based on the limited info available as you say) on how the increase in potential between Neutral and 'true' earth would cause the RCD to trip.

Have I missed something (it wouldn't be the first, or last time!)?

 

[steptoe]

I have no issue with Steps views on earthing, or the importation of a fault into an installation if there is an external PME fault. I also fully understand your, more eloquent description on the same thing.

I can't argue either with Special Location's description of three phase generation.

All good stuff.

My problem (and without putting words in their mouths, I think ADS and Andy's also) is that I can't see how any of this would cause the OP's RCD to trip.

When I read your earlier posts, I got to the end of the second instalment, and expected a third, the punchline, which drew it all together and expressed your conclusion (based on the limited info available as you say) on how the increase in potential between Neutral and 'true' earth would cause the RCD to trip.

Have I missed something (it wouldn't be the first, or last time!)?

RCDs work on a balance of L N, if the current in L & N do not match then the RCD trips.

if you import a fault into a PME install you now have a current on the E that shouldnt be there,

as N & E are essentially the same cable on a PME then it would be logical to assume this extra current on the E will also be present (in part) on the N, therefore we now have a N cable carrying more current than the L, the RCD will detect this difference between the L & N and do what it is designed to do.

this current wont simply flow down the E back to the cutout and look for the oneway sign back to star, it will be omnipresent on all parts of the system although the majority of it will flow through the path of least resistance,(most likely back to star point).

[a bit like pouring water into a bucket with lots of different size holes in it, the water will come out all the holes, not just the largest one.]

in a normally functioning system the imbalance will usually be due to the current that should be on the N being diverted to E, thus the N being at a lower current than L, but the RCD isnt smart enough to know this, it just "sees" a difference between L & N and trips.

[ apologises guys, no pic yet, wading through mounds of paperwork for a course next week and my computer is refusing to upload the drawing I have, will try again tomorrow, technology and me dont gel too good. X( ]

 

[Riggy]

RCDs work on a balance of L N, if the current in L & N do not match then the RCD trips.if you import a fault into a PME install you now have a current on the E that shouldnt be there,

as N & E are essentially the same cable on a PME then it would be logical to assume this extra current on the E will also be present (in part) on the N, therefore we now have a N cable carrying more current than the L, the RCD will detect this difference between the L & N and do what it is designed to do.

this current wont simply flow down the E back to the cutout and look for the oneway sign back to star, it will be omnipresent on all parts of the system although the majority of it will flow through the path of least resistance,(most likely back to star point).

[a bit like pouring water into a bucket with lots of different size holes in it, the water will come out all the holes, not just the largest one.]

in a normally functioning system the imbalance will usually be due to the current that should be on the N being diverted to E, thus the N being at a lower current than L, but the RCD isnt smart enough to know this, it just "sees" a difference between L & N and trips.

Thanks for that, can see your logic, but I see all of this happening on the upstream (supply) side of the RCD, in which case no imbalance?

Please understand, I'm trying to understand, not argue!

 

[Andy™]

RCDs work on a balance of L N, if the current in L & N do not match then the RCD trips.if you import a fault into a PME install you now have a current on the E that shouldnt be there,

as N & E are essentially the same cable on a PME then it would be logical to assume this extra current on the E will also be present (in part) on the N, therefore we now have a N cable carrying more current than the L, the RCD will detect this difference between the L & N and do what it is designed to do.

this current wont simply flow down the E back to the cutout and look for the oneway sign back to star, it will be omnipresent on all parts of the system although the majority of it will flow through the path of least resistance,(most likely back to star point).

and your completely missing the fact that any extra current that flows through the neutral of the RCD must also flow through the live side (since it cannot dissapear into thin air), and so there is no imbalance.

 

[green-hornet]

I have followed this with some interest, I have also done a little research not intensive but research all the same.

This is a common fault and is very seldom reported, simply because people do not believe that downstream faults can effect your RCD.

A similar fault occured up in the Durham area with overhead power supply, two seperate phases where affected and every night when the street lights were turned on, hey presto one ladies RCD tripped out.

Turns out to be a high resistance on the nuetral, coupled with a sudden high demand on a particular phase on the supply caused the RCD to feel this imbalance and do its job and trip.

Now if we relate this effect to the OP we will have to ask why this is happening,I would think it is possible that all the houses in this area are some distance from the distribution, and all PME, and all will have a high Ze because they are almost end of line.

The High resistance of the neutral would effect some but not all houses, and if a particular RCD is very sensitive then perhaps that one is the only one effected.

I do not know, all I do know is that outside influences have been reported to effect the operation of RCD's, and it is well within the realms of possibility that this is the cause of this problem for the op.

Conclusion

Shoot the lawnmower man

 

[Riggy]

For info, I had a VERY similar issue on a caravan site.

The park, or part of it at least, was flooded during Cumbrian floodings last November. (Coincidently I was working there 10 days ago when the shootings were going on 15 miles away last week!)

Anyway, 12 new hook-ups with associated works, PIR on each new van as they arrive and are connected, etc.

First van to be sited is connected and tested, no probs. Second one ditto, and the third.

Now, joiner starts building decking around first van, RCD trips in van 3. They are on different circuits and different phases. I didn't witness it, but owner was adamant that RCD tripped when joiner used chop saw. Tested everything in both vans again (joiner had gone by this time) all fine. Changed RCD which had tripped, more in the interests of customer relations if I'm honest, no problem since. Joiner has been back and was 'forced' to use the chop saw to see if anything tripped - nothing did. Everyone's happy, except for me, I'm confused!

 

[Andy™]

could be some kind of interference.

see this thread - maybe somewhat related (and i never did find out what the problem was - it still happens)

 

[green-hornet]

That would prove that a very sensitive RCD noticed an inbalance when others did not, and again goes to prove that downstream faults can effect the operation of a RCD.

 

[Riggy]

That would prove that a very sensitive RCD noticed an inbalance when others did not, and again goes to prove that downstream faults can effect the operation of a RCD.

Upstream?

 

[green-hornet]

Or that

 

[steptoe]

I have followed this with some interest, I have also done a little research not intensive but research all the same.This is a common fault and is very seldom reported, simply because people do not believe that downstream faults can effect your RCD.

A similar fault occured up in the Durham area with overhead power supply, two seperate phases where affected and every night when the street lights were turned on, hey presto one ladies RCD tripped out.

Turns out to be a high resistance on the nuetral, coupled with a sudden high demand on a particular phase on the supply caused the RCD to feel this imbalance and do its job and trip.

Now if we relate this effect to the OP we will have to ask why this is happening,I would think it is possible that all the houses in this area are some distance from the distribution, and all PME, and all will have a high Ze because they are almost end of line.

The High resistance of the neutral would effect some but not all houses, and if a particular RCD is very sensitive then perhaps that one is the only one effected.

I do not know, all I do know is that outside influences have been reported to effect the operation of RCD's, and it is well within the realms of possibility that this is the cause of this problem for the op.

Conclusion

Shoot the lawnmower man

:Applaud :Applaud

or drive an earth rod through his heart...

[quote name='Andy

 

[Andy™]

not from a different phase it cant

unless there is a fault RCD side (in which case RCD is working as it should), then any current flowing through one conductor must also flow through the other. there is no other path the current can take

 

[Sidewinder]

Riggy,

I will do a part 4, I have been a bit busy, with pc problems!

For now, it is possible for upstream disturbances to trip an RCD. This can be due to an imbalance on the incoming wiring caused by loads and or faults on the DNO network

 

[steptoe]

that is why the RCD trips,

an imbalance in the N will trip the RCD when it is trying to feed 400v from a different phase.

regardless of where the fault is, the current is omnipresent on all of the neutral cable.

headbang

 

[Lee321]

a pic will really help this thread i think