broken neutral?

[stormy457]

A friend of mine has a mobile home which was experiencing loss of supply, on investigating it was found that certain parts of the chassis was live, so her husband put in two earth rods. The following day the mobile home park owners said that these earth rods had caused the following faults
a} the supply increased to 350 volts live to earth, which would normally be 240
b} 150 volts neutral to earth, which should be zero
c} 88 volts live to neutral which should be 240 volts.
A number of homes experienced loss of supply and appliance damage, and one home had a fire, I cannot see how these earth rods would cause such a catastrophic problem which is what is being alleged, to me this sounds like a loose, lost or damaged connection of the neutral conductor at the star point of the main supply transformer, or the bonding of that neutral conductor at a local earth point. Any ideas? My thanks in advance.

 

[Guest123]

Hi.

Bit of a toughy to get my head round this one.

Certainly sounds like the pitches/hook ups, have been supplied via a TN-C-S system which is against both BS 7671, and the ESQCR, for the very reason that appears to be present here when the supply PEN coductor goes open circuit.


Obviously the load on the hook ups is still drawing current but with the return path shorting out, the return current has nowhere to go as the neutral is also the earth in TN-C-S, other than onto the bonded steelwork of your caravan/mobile home.

By installing the rods he may have inadvertantly created another path to earth for the stray current which may have travelled through the general mass of earth and back up to any other mobiles that also has earth rods installed.

But there again the excess voltage would suggest a supply Tx problem

Where did you measure your voltage readings at as there must have been L,N+E there of some description???

Were there any existing earth electrodes present before the ones that your friend installed???

Have you contacted the DNO to come and investigate???


Sorry for all the questions, just trying to get a clearer picture.

 

[mechelec]

does sound like a suppliers neutral problem, it is the only way the voltage can "shift" to give such high phase to earth values

 

[stormy457]

Hi, sorry for the delay in replying
I will try and answer your questions as best I can,
We have not asked the DNO to come and investigate The mobile home park electrical infrastructure is being maintained by Southern Electric Contracting {SEC} which appears to be a subsidiary of Scottish and Southern Energy {who presumably are the DNO}. presumably the parks electrical equipment and responsibilities start at the sites distribution transformer.
I am not sure where their readings were taken from but there was an earth electrode present on the mobile home before the two were put in later. I assume this is the case with all mobile homes on the site.
There is not a main RCD present however, in fact this is the case with alot of the homes on the park, mainly the older ones. I don't know whos responsibility it is to ensure that the home is equipped with one or from when one should have been installed. Is it the site owner or the individual home owner that should ensure a main RCD is present on each home? Are older homes exempt from having them because they were built before the regulations came into force?
Just for your information it seems that about 45-50 homes were affected with loss of supply and electrical equipment malfunction. Thankyou for all your help on this Lenny and Mechelec. Very grateful.