installer44 Posted April 7, 2009 Share Posted April 7, 2009 Whats the possible fault when you get a voltage between neutral and earth trying to sort a job where im getting about 15 volts. Link to comment Share on other sites More sharing options...
sparky999 Posted April 7, 2009 Share Posted April 7, 2009 Whats the possible fault when you get a voltage between neutral and earth trying to sort a job where im getting about 15 volts. Could be several faults such as water ingression or a trapped cable. If this is on a ring main you will have to break it down. Pete Peter Robinson Freelance M:07889038650 Link to comment Share on other sites More sharing options...
luggsey Posted April 7, 2009 Share Posted April 7, 2009 Is it TT earth or PME, TT can do weird things as can PME faults. Most likely cause is induced voltage, try turning off all other circuits and testing then. I presume you have done 500 volt insulation tests? ----------------------------------------------------------------------------------------------------------------------------------- Life is like a box of chocolates, some bugger always gets the nice ones! My Amateur Radio Forum Link to comment Share on other sites More sharing options...
y-i-out-of-bed Posted April 7, 2009 Share Posted April 7, 2009 it could be meny things is there any IT equipment there? or could be earth leak from an applience or cable Link to comment Share on other sites More sharing options...
lawandorder Posted April 7, 2009 Share Posted April 7, 2009 It may not be faulty at all, what are the earthing arrangements? Link to comment Share on other sites More sharing options...
SUBS Posted April 8, 2009 Share Posted April 8, 2009 What are you reading it with ? A DMM has such a high OPV that readings like tis can be confusing, try it with a 20,000 OPV analogue meter, or just put a resistor across the probes and see what changes. You might find there not a fault there at all, just some induced voltage, a reading through the capacitance in surge a limiter somewhere, or something like that. Link to comment Share on other sites More sharing options...
motco Posted April 9, 2009 Share Posted April 9, 2009 I seem to recall that neutral is earthed at the power station or local sub-station, and a small voltage can often be detected on the neutral conductor caused by the resistance of the neutral supply cable somewhere. Might be dreaming though... Link to comment Share on other sites More sharing options...
james.wilson Posted April 9, 2009 Share Posted April 9, 2009 you got a voltage on the neutral when the star point is not in the centre. This is caused by improper phase balacing securitywarehouse Security Supplies from Security Warehouse Trade Members please contact us for your TSI vetted trade discount. Link to comment Share on other sites More sharing options...
DirectFS Posted April 9, 2009 Share Posted April 9, 2009 Whats the possible fault when you get a voltage between neutral and earth trying to sort a job where im getting about 15 volts. Could be many things. Much depends on where you're taking your measurement from and how. What else is connected to the circuit you've pulled your supply from? e.g. IT equipment, white goods? Is the 15V measured at the board with circuits disconnected - e.g. is the fault on the supplier side or on the installation side? It could also be poor connections, loose wiring, faulty wiring (e.g. a cable cut which has also cut inner sheathes), - an insulation test at 500V as someone said will answer that for you. Someone also said that it could be reliant on the type of earthing arrangement for the installation - TT, for example, is earthed using copper rods driven into the ground, whereas with a TN type system, you have an earth supplied with the phase couresty of your friendly local supplier. As to how this is provided, depends on a number of factors - TN-C is supplied bonded to neutral (also known as PME) though arrives often as two seperate terminals - as in a phase, neutral and a tap for earth, so there should in theory never be any variance on the supplier side, whereas TN-S is supplied as a seperate earth. There are other earthing systems too, though not common in the UK any longer. Most of the UK is TN-C, though both TN-S and TT exist copiously in rural areas (especially where supplied by overhead cable). So, without knowing much of the above, it is hard to give any sort of definitive answer...... Bill. Bill Accord Fire & Security Services Ltd. www.accordfire.co.uk ~ TEL: 0845 474 5839 Link to comment Share on other sites More sharing options...
luggsey Posted April 9, 2009 Share Posted April 9, 2009 I seem to recall that neutral is earthed at the power station or local sub-station, and a small voltage can often be detected on the neutral conductor caused by the resistance of the neutral supply cable somewhere. Might be dreaming though... You could see this if the supply company neutral is high z and you or someone on the same supply phase has a neutral earth fault, the difference in potential will make really weird things happen! James your description of a star point not being in the middle baffles me, can you explain what you mean a bit more? ----------------------------------------------------------------------------------------------------------------------------------- Life is like a box of chocolates, some bugger always gets the nice ones! My Amateur Radio Forum Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.