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Topic Title: Replace delta generator with Y
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Created On: 15 August 2013 03:43 PM
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 15 August 2013 03:43 PM
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Peddler

Posts: 36
Joined: 28 May 2008

HI Folks,

I have a faulty generator , its 600v 60 Hz , ( Engine is fine ) the offshore tech tells me its wired in Delta , no Neutral so I assume its an unearthed generator ( Floating ) but im still waiting on confirmation of this. I have sourced a 600v 60hz generator 4 wire star wound generator . I dont have much experience in using unearthed systems , its on an old drilling rig and they use unearthed systems in case there is a short circuit and the drill gets stuck, as there is no path to earth no fault current can flow and it wont trip the supply , this enables them to keep the drill rotating so they can get it back out of the hole.
Now this rig no longer drills so as far as I can see an unearthed system isn't required anymore

question i have is can I use this star 4 wire generator and float the Neutral ?

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You can Learn from an Apprentice
 15 August 2013 04:07 PM
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MickeyB

Posts: 181
Joined: 18 January 2003

Could you insert a resistor and make it an IT system with monitoring? Failing that operating a star with no reference is no different to a delta if you have no device to trip? Voltage stability for unbalanced loads?
 16 August 2013 07:41 AM
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Peddler

Posts: 36
Joined: 28 May 2008

Hi Mickey,

thanks for the reply ,

There is an over current relay and under voltage relay on the panel which opens the breaker if activated.

I've asked a few people yesterday about this and they are also saying the same thing as you that it makes no difference at all. Obviously as long as the voltage is the same.

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 18 August 2013 12:12 PM
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ArthurHall

Posts: 737
Joined: 25 July 2008

Peddler
600V IT systems are very common on drill rigs, you probably already have earth monitoring, or should have. Remember that the neutral will have to be insulated so that the system will still work if you have a phase to earth fault.
 18 August 2013 12:26 PM
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ArthurHall

Posts: 737
Joined: 25 July 2008

Forgot to say, have you consulted the IEE regs for offshore platforms? Also HSE guidance note 9/2005 Safe operation of unearthed electrical distribution systems.
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