Very high earth loop readings

[alanmcm]

Was out doing some defect repairs on a system with a few high earth loop readings. I had previously been on site and tested the circuits with the high readings. For one of the circuits I had a reading of 1.28 ohms for a C50 t/p mcb it was rather high. So the idea was to remove the mcb and replace with 3 fuses and a carrier with the auxillary going through a voltage monitoring relay as the circuit was supplying a motor (don't want that burning out). So fitted everything and everything was running as it should and I repeated the earth loop test and got a reading of 6.28 ohms. I then tested the next circuit I had done across the yard and it was reading 5.76 ohms.

I thought maybe had done something wrong so I tested a circuit as close to the main incoming supply as possible and was getting a reading of 5.46 ohms. So went and tested earth loop at the source and again another reading of 5.46 ohms.

Background for this story is that there is a neighbouring famer who shares a lane with this cement yard. Previous owner of cement yard used to pay farmer a fee for the inconvenience but new occupiers (8 years ago) wont. So he has burnt down containers within the yard, used forklifts to rip security cameras down and ripped fences down. He even comes down to 'borrow' cigarettes, his latest escapade has led him to rip the roof off the top of the sub room. Its been off for a few weeks now and the supply to the cement yard is directly below the hole in the roof. With the cable going into the isolator from the top, its getting soaked as its been bushed through. (pics to follow) The earths in this room all converge into one isco and I followed one of them out through a hole in the wall and found in has been broke using a digger. The mains room is on the farmers land and the cables run underground over to the plant. There is fresh dirt around the mains room.

I'm still technically a trainee engineer (Passed HNC electrical and Electronic, not the usual proper sparking quals) and most of my work is around a quarry and I don't usually deal with inspection and testing practices or earthing arrangements.

Original inspection gave a reading of 0.19 ohms 25mm cable conductors and same size for the earth, TN-S setup. I cant see the earth from the supplier anywhere, surely it follows the supply? Would they put the earth directly to the site and bypass the mains room where the supply cable is and their own 100a fuses? The cables leave the fuses and go to the meter above and then head over to another panel which supplies the site itself. Outside the room there is a transformer which has an earth cable running down it but I haven't a clue where it goes from there. Not looking definitive answers so as to go and fix it, I'm trying to further my knowledge to better understand it all.

Side note, our company are just doing defect repairs and haven't created this masterpiece.

 

[Deleted member 9648]

Cant see where TNS looks at all likely, there's nothing on the heads or incoming cables....is it a TT ?

 

[alanmcm]

I got TN-S from the inspection report and that's why I'm confused about the actual earthing arrangement. There is a bare earth cable coming through the plaster off the wall, not sure whether or not this is the main earth, but it looked too small. The biggest earth I could find is from the banjo bolt on the bottom of the cement yard supply panel going to the ISCO

 

[mattg4321]

Only a guess but it looks like a TT system and the last EICR was probably just made up.

Can you trace any cables going outside to a rod maybe?

 

[stevethesparks]

Off topic but pic 4 reminds me of how stupid it was to harmonise cable colours that conflicted.

 

[alanmcm]

Couldn't trace it as it goes onto the farmers land and I reckon a pitch fork and me running very fast would occur.

The larger earth goes between the isco and the panel. The smaller earth at the bottom that follows the cables out the gap in the wall is broke, I pulled it out of the earth. The earth wouldn't be brought direct to the site and not follow the supply cable? Just thinking that if that has happened then its why I cant see the earth and the farmer has broke it. I guess its up to the electric board now to confirm continuity on it.

When I measured my earth loop I used L1 from supply side and then onto that crazy grouping of earths below and got the reading. Would the water in the bottom of the panel affect the reading. I didn't have the lead testing through the water and I dried the panel as best I could.

 

[Deleted member 72666]

'Neighbours from Hell' springs to mind! I feel for both you and your client.

 

[alanmcm]

Ive now left it in the capable hands of the electric board. 3 weeks ago the readings were above what they should be as per the regs and the remedial work I completed should have made them comply but the readings having changed dramatically I feel ive done everything I could to rectify it. Well I hope I have and I haven't done anything silly, but I feel semi-confident I followed everything Ive been taught and thanks to anyone who has replied and for future replies.

Ill update more when I find out the truth, told the company to put the roof back on first, incase the electric board see the rain that can run into it and just remove the fuses and shut them down.

 

[DPG]

How did you get on with this one? Daz

 

[westward10]

Am I missing something, the picture of the service head shows no earthing conductor. Due to the type of premises and possible remoteness of the supply it looks like the DNO is not happy to put in place an earthing system. It should be TT I should imagine, or knowing farmers no system exists at all.