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Topic Title: IT earthing system on 3-phase generator
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Created On: 17 July 2012 03:55 PM
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 17 July 2012 03:55 PM
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ftsouza

Posts: 2
Joined: 17 July 2012

We manufacture polyethylene welding track machines. These machines has onboard 3-phase generator 240V, 22KW.
We design our machines based on IT (isolated) earthing system.
The generator provides power specifically to the welding system (heater, facer, etc.) there is no power outlet to connect any external device to the onboard generator.
We are looking for Australia and England requirements with regards the use of "stand alone" generators in IT earthing systems?
Since a RCD/GFCI will not work properly on this systems, what the exception or requirements?
thanks in advance.
Fabiano.
 17 July 2012 04:59 PM
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ArthurHall

Posts: 735
Joined: 25 July 2008

The normal system is to use an insulation monitor which alarms if there is an earth fault. In addition all parts of the installation must be insulated to the full phase voltage.
The UK HSE publish an offshore instruction 2/2011 which details precations to be taken on offshore installations where this system is common.
 18 July 2012 10:04 AM
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AJJewsbury

Posts: 11269
Joined: 13 August 2003

I wonder if the setup is closer to a separated (413 or possible 418.3 in wiring regs terms) rather than IT - generally similar but usually no demand for insulation monitoring. Separated systems for small generator supplied setups are pretty common in the UK.
- Andy.
 19 July 2012 09:37 AM
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zeeper

Posts: 1407
Joined: 11 July 2008

might I suggest you have a look at BSEN 60204-1 . Page 45, 8.2.7 mentions mobile machines with on board power supplies.
 20 July 2012 11:05 PM
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ftsouza

Posts: 2
Joined: 17 July 2012

You right Arthur,
Our generator arrangement is a separated system. The generator winding is connected in start with no neutral conductor.
What I have found (AS/NZS 3000 section 7.6.3, 7.4 & 7.4.2 ) is that for portable generator arranged as a separated supply a RCD is not required. In order for a RCD works properly in a 3-phase system, the neutral conductor shall be bonded to the generator bonding system.
I still need to make sure England has the same requirements. i am looking for the right standard that cover portable generator.
Thank you all
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