I think I have a faulty 66kva transformer but have little to no experience with them (delta star I believe)
Call out due to reported problems from some of the tenants (offices that are rented within part of the building)
some RCD protected ring final circuits disconnecting. Investigated at the local sub-main distribution board and discovered some strange goings-on... The voltage of all three phases with reference to each other and with reference to neutral are as you would expect. When L1, L2 & L3 were tested with reference to earth I have readings of 130, 290 & 380 volts (approximate values) the voltage from earth to neutral is 130 volts.
I toddle off to the factory side of the installation and when on site I am greeted by "electricians" scratching their heads and removing RCD socket outlets and replacing for standard.
I make my way over to the substation with a privately owned 6.6kva transformer. The 1st part of the installation is a bus bar chamber. I gingerly remove the lid and see that one of the 3 phases is shorting with the neutral... Booyah; I've found the problem. I isolate the supply, separate the phase conductor from the neutral conductor and re-energise. I test the installation, pat my self on the back and go home.
Today I get called out due to the same symptoms. I go to the original distribution board within the offices and discover that the same problem exists. Back over to the substation I go and the same readings are observed. I gingerly check the neutral conductor is mechanically sound and i'm satisfied that it is. The earthing arrangement inspires confidence to, 2 earth rods within enclosures, a good connection to the casing of the transformer and a sound connection to the isolation switches and busbar chamber
maybe one for Engineer54? ...if you're not to busy bashing partP and the NICEIC
Thanks Rob, I'm not sure of the size of the transformer
Edited for simplicity:
the secondary side of my delta star transformer appears to generating 3 phase perfectly and a good, mechanically sound, centre tapped neutral. the voltages I observe with reference to earth (across each phase and to neutral) would suggest that the earth is poor. But how can it be with the following arrangement; 2 x earth rods to side of transformer, earth connection on casing of transformer, earth bar running the length of the wall (about 12 inches off ground and showing signs of discolouring (not sure what this is for)) and 10 earth cables leaving the room to various extraneous conductive parts ie; gas, water, structural steel etc..
And why would the installation remain energised while L3 has been sat in contact with the neutral conductor?
Call out due to reported problems from some of the tenants (offices that are rented within part of the building)
some RCD protected ring final circuits disconnecting. Investigated at the local sub-main distribution board and discovered some strange goings-on... The voltage of all three phases with reference to each other and with reference to neutral are as you would expect. When L1, L2 & L3 were tested with reference to earth I have readings of 130, 290 & 380 volts (approximate values) the voltage from earth to neutral is 130 volts.
I toddle off to the factory side of the installation and when on site I am greeted by "electricians" scratching their heads and removing RCD socket outlets and replacing for standard.
I make my way over to the substation with a privately owned 6.6kva transformer. The 1st part of the installation is a bus bar chamber. I gingerly remove the lid and see that one of the 3 phases is shorting with the neutral... Booyah; I've found the problem. I isolate the supply, separate the phase conductor from the neutral conductor and re-energise. I test the installation, pat my self on the back and go home.
Today I get called out due to the same symptoms. I go to the original distribution board within the offices and discover that the same problem exists. Back over to the substation I go and the same readings are observed. I gingerly check the neutral conductor is mechanically sound and i'm satisfied that it is. The earthing arrangement inspires confidence to, 2 earth rods within enclosures, a good connection to the casing of the transformer and a sound connection to the isolation switches and busbar chamber
maybe one for Engineer54? ...if you're not to busy bashing partP and the NICEIC
Thanks Rob, I'm not sure of the size of the transformer
Edited for simplicity:
the secondary side of my delta star transformer appears to generating 3 phase perfectly and a good, mechanically sound, centre tapped neutral. the voltages I observe with reference to earth (across each phase and to neutral) would suggest that the earth is poor. But how can it be with the following arrangement; 2 x earth rods to side of transformer, earth connection on casing of transformer, earth bar running the length of the wall (about 12 inches off ground and showing signs of discolouring (not sure what this is for)) and 10 earth cables leaving the room to various extraneous conductive parts ie; gas, water, structural steel etc..
And why would the installation remain energised while L3 has been sat in contact with the neutral conductor?
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