A
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.
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.
