Ungrounded Phase Voltage

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parthasarathy82 Participant Join Date: May 2013 Location: Auckland Posts: 3	Ungrounded Phase Voltage 03/03/2014 4:32 AM
	on Board a Ship Ungrounded system is used so when i measure the voltage between phase to hull i am getting the 1.732 time of the phase value, which is just like grounded system ... how and why?
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Tornado Guru Join Date: May 2009 Location: Richland, WA, USA Posts: 21017 Good Answers: 795	#1 Re: ungrounded phase voltage 03/03/2014 5:41 AM
	Possibly because you have an unintentionally grounded phase. __________________ In vino veritas; in cervisia carmen; in aqua E. coli.
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RAMConsult Guru Join Date: May 2007 Location: NYC metropolitan area. Posts: 3230 Good Answers: 444	#2 Re: Ungrounded Phase Voltage 03/03/2014 8:56 AM
	Because you're using a digital meter and it's picking up the capacitive coupling between the windings and the iron. Try it with an analog meter like a Simpson 260, if you still get the voltage then you do have a single fault somewhere that you better find before the second one occurs. __________________ “Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
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TonyS Guru Join Date: Aug 2010 Location: Resting under the Major Oak Posts: 4347 Good Answers: 181	#3 Re: Ungrounded Phase Voltage 03/03/2014 7:54 PM
	Somewhere in the system you have a neutral → earth (ground) fault. The voltage won't be as you say x √3 Ph→Ph it will be /√3 Ph→Ph. __________________ The reports of my death are greatly exaggerated.
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NotUrOrdinaryJoe Guru Join Date: Apr 2008 Location: Lexington, KY Posts: 1639 Good Answers: 73	#4 In reply to #3 Re: Ungrounded Phase Voltage 03/05/2014 1:28 PM
	Tony is probably right. Since we can't see the equipment on your ship, and we can't determine if somebody plugged in some equipment that connected the chassis of that device to the ship. If you are lucky, it is just a low current path that is made through capacitive linkage. If your not, you may find that equipment attached to the ship through a bit of accidental welding to the chassis. It really depends on how many offenses and how severe they have been with respect to the on board electrical system. It wouldn't be the first time this has happened. __________________ A great troubleshooting tip...."When you eliminate the impossible, whatever remains, however improbable, must be the truth." Sir Arthur Conan Doyle
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