An interesting read

[matt1e]

tbh if it is as easy as go TT, I will be!

Not without a neutral you wont

I don't think anyone is suggesting, or could be suggesting, that there is no neutral. After all, all the affected houses seem to have usable supplies, give or take the RCD tripping.

Kind Regards, John.

Hi john he has 7 amps flowing through his main earthing conductor that disappears when they connect an earth stake to the MET (it shorts the current flow out) therefore the current flow has to be from the MET
and since this derived from the neutral connection then the current is
flowing from the neutral conductor to ground as apposed to from the neutral conductor back to the star point
he has a broken/high impedence neutral conductor between the transformer and his house
and since he is first to be served by the transformer and the supply is overhead line then there is more than just him that has a faulty neutral
given

they pulled the service fuses in both houses (and broke ours so a nice new one now) and 3A was still present.

this 3A is coming via tho op's neutral conductor from somewhere (neighbouring properties) when it should be heading back along the poles to the transformer

andrew any chance of some pictures of your cutout, main bonding poles etc ?

Matt

 

[andrew1210]

Hi, I am able to give pic's of CU and meter, cutout in this post. will get bonding later if necessary, as it's pretty inaccessible!

Below shows the setup, the black cable leaving the cutout feeds next door (semi-det) via our loft to their CU.

View media item 35625 View media item 35626 View media item 35627

 

[matt1e]

Hi, I am able to give pic's of CU and meter, cutout in this post. will get bonding later if necessary, as it's pretty inaccessible!

Thanks Andrew No need for the bonding Pics it's how I thought It would be
(connected in the CU as apposed to the MET)


Matt

 

[JohnW2]

Hi john he has 7 amps flowing through his main earthing conductor that disappears when they connect an earth stake to the MET (it shorts the current flow out) therefore the current flow has to be from the MET..... this 3A is coming via tho op's neutral conductor from somewhere (neighbouring properties) when it should be heading back along the poles to the transformer

OK. It seems that my head has not got itself around this properly. Allow me to think aloud ....

...as I understand what you're saying, this 3A is flowing from neighbouring properties along the neutral supply conductor (on the 'properties side' of the break/fault), to the OP's cutout, via the N-E link in the cutout, thence along the earthing conductor to the MET. Is that correct? If so, I don't understand why it would disappear when one connected an earth spike to the MET; if anything, I would expect that additional path to earth to increase the current in the earthing conductor slightly.

Can you put me right?

Kind Regards, John

 

[sparkticus]

...as I understand what you're saying, this 3A is flowing from neighbouring properties along the neutral supply conductor (on the 'properties side' of the break/fault), to the OP's cutout, via the N-E link in the cutout, thence along the earthing conductor to the MET. Is that correct? If so, I don't understand why it would disappear when one connected an earth spike to the MET; if anything, I would expect that additional path to earth to increase the current in the earthing conductor slightly.

The only way I could understand that happening as described is if the temporary spike has a significantly lower impedance (Low Ra) then it would take the lions share of the current (since it is in parallel with the OPs earth connection at the actual cut-out as opposed the the MET) The temp spike being connected to the MET.

But from the picture it looks to me as though this is PME so if the temporary rod really does give a lower impedance then both the Earth and Neutral (from the OPs house to the transformer) seem to have problems.
I think I read earlier that the PME was a bit suspect? Records show TT etc...

 

[andrew1210]

Hi, yes, records showed TT, still a big ? over that though!

If it helps the spike was hammered into our front grass where the ground was very very wet with 3ft of quickly melting snow!

 

[sparkticus]

Yes, so if they are measuring the 3 - 7 amps of current at your cut-out earth position (not your MET in the CU) when they connect a low impedance spike to your MET (in your CU) then assuming the Ra of the temp spike is significantly lower than the path back through your cut-out, most of the current will now flow via the new tem spike. Suggesting that the neutral from your house to the transformer star point is O/C or very high impedance as is any earth cable (which may or may not exist in this case)

 

[matt1e]

Yes John I'll try, I've included the earlier drawing as it might help
It is to do with the way the ops bonding is connected
the neutral current is trying to find the easiest route back to the transformer
so it travels along the unbroken neutral where it finds a path to earth via the ops bonding
because the ops bonding is connected at the CU it has to travel from the MET along the main earth conductor to get there
when you connect the met directly to the earth rod then it takes that route instead because in this case its obviously an easier route.
if the main bonding was connected directly to the met then the current flow would not have shown up on the main earth
It has to be said that not all the neutral current will be travelling via the ops bonding as there we be loads of parallel paths due to everyone elses bonding and existing E/N faults
also in not all cases would connecting a stake to the met give the result that the ops case does as the current flow might still find the bonding route easier
in certain cases
But in the op's case they got a result (but don't seem to know what it means) so why they bothered to do it is anyones guess
Matt
View media item 35541

 

[andrew1210]

I personally told the contractor this that they sent out. "Could it be a broken neutral between here and the transformer"

answer: "quite possibly, although the fault could be coming from this house"

even though this has all been checked on more than one occassion

WELL WHY NOT SEND SOMEONE OUT WHO CAN LOOK AT THE WIRING BETWEEN THE HOUSE AND THE TRANSFORMER!

 

[matt1e]

Sparkticus has his head round it
Apart from they are connecting the stake at the cutout position not the CU
Matt

 

[JohnW2]

Yes John I'll try .... the neutral current is trying to find the easiest route back to the transformer so it travels along the unbroken neutral where it finds a path to earth via the ops bonding
because the ops bonding is connected at the CU it has to travel from the MET along the main earth conductor to get there
when you connect the met directly to the earth rod then it takes that route instead because in this case its obviously an easier route.

Thanks - but, sorry, I'm not there yet....

....given my understanding that we're talking about current coming from other properties, via an unbroken bit of the neutral conductor, that current surely has to travel 'up' the earthing conductor from N-E link in the OP's cutout to the MET (in which earthing conductor I presume, it's being measured with a clamp meter). As you say, it then is finding a path to earth via bonding.

If one connects an earth spike to the MET, one has merely improved (somewhat) that path to earth. The current from the neighbouring properties (perhaps now slightly greater) still has to travel up the earthing conductor from cutout to MET in order to find a path to earth - so the measured current in that conductor surely ought to remain there (probably increase slightly), not 'disappear'?

I agree that the current in the conductor between MET and CU/bonding will diminish (but not dissapear), due to the current to earth now being shared between the bonding and earth spike - but I thought we were talking about the current in the earthing conductor from the cutout to MET.

Kind Regards, John.

 

[sparkticus]

Sparkticus has his head round it
Apart from they are connecting the stake at the cutout position not the CU
Matt

Ah right at the cut-out. but yes, this is a broken or high impedance neutral from he OPs property to the tranny. The poor DNO records (why am I not surprised because today Western Power could not even tell me if a property was PMEd recently or not) are causing additional confusion.

Looks like a job for a big digger to me

 

[andrew1210]

Looks like a job for a big digger to me

Yes, I think SP would rather go into administration by wasting money on engineers doing nothing before biting the bullet and sending out a digger!

It's as if it can't be possible that there is a fault on there network, locally dated to 1939! how dare I imply this!

 

[sparkticus]

John, I think it is only a case of where you place the clamp meter. To the right or left of the temp spike connection point.

If the temp spike is at the cut-out and clamp meter to the left (on the G/Y in the picture between cut-out and MET/CU) then you will see only residual current. If you then remove the temp spike you will see the 3 - 7 amps again.

I say residual current but obviously it will be determined by the ratio of the two impedances (the temp spike-lower, the broken neutral-higher)

 

[JohnW2]

John, I think it is only a case of where you place the clamp meter. To the right or left of the temp spike connection point.

True, but in my exchanges with Matt, I've been working on the basis of his drawings - which show the clamp meter bewteen cutout and MET/CU/bonding. With that arrangement, I really don't think one should see even a decrease (probably a small increase), let alone a 'disappearance', of the current when one connects an earth spike to the MET (or CU)- which, again, is where Matt said the earth spike was attached.

Kind Regards, John