# To ground or not to ground?



## MDShunk (Jan 7, 2007)

Didn't we just go over this the other day, or am I nuts?


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## delsol (May 30, 2009)

yes sir but...

I am trying to get my head around the grounding of the xo and what caused the melting of the conductors. 

Would you normally terminate the _grounding_ conductors on xo when there are no neutrals present fro DG system and the primary is also grounded?

Did the grounding conductors melt because the transformer went into ferroresonace when B phase opened on the pole?


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## RePhase277 (Feb 5, 2008)

delsol said:


> yes sir but...
> 
> I am trying to get my head around the grounding of the xo and what caused the melting of the conductors.
> 
> ...


I'm still curious why, if there is no neutral on the 480, the transformers are wired wye/wye? Also, the blown B phase fuse, if it was the fuse feeding the lines into the grid, then there had to be an overload or short that caused that fuse to blow. It had to be downstream of the fuse. So a line fault likely ocurred, blowing B fuse and melting your ground before the fuse opened.

In the system you describe, it seems like it would be best to have it set up delta/wye. Ground the neutral wye point. But a wye primary, with the neutral floating, seems like you would get strange secondary voltages depending on loading. I don't know this for a fact, but my gut says something strange would happen, at any rate.


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## j johnson (Jul 20, 2009)

Do not ground H0 pont of tranformer.


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## bobelectric (Feb 24, 2007)

delsol said:


> Distributed generation system
> 
> 
> 
> ...


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## MDShunk (Jan 7, 2007)

bobelectric said:


> I would say I wired it to the engineers drawinigs.


:laughing:

Along the lines of an RFI, I'd like to propose a new form to send to engineers. An AYS form, for "are you sure" ...that you really want it done this way.


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## s.kelly (Mar 20, 2009)

talked to a guy I'm working with this week about his engineer student brother. He was helping him move into an apartment, and furniture was laid out according to his drawings. The electrician says on the way to the new place he will bet dinner the drawing will not work, eng. in training says of course it will.... guess who bought dinner

seems he forgot molding around windows etc in his floor layout!


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## Toronto Sparky (Apr 12, 2009)

I have never seen 3 phase power created by inverters.
How is that done? 
I would have thought M/G set.

Guess I'm getting too old for new technology.


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## Richard Rowe (May 25, 2009)

Have you found out what happened to the B phase??? Thats the key I would think. How long did this set up run before the melt down?


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## mpoulton (Jul 17, 2009)

Toronto Sparky said:


> I have never seen 3 phase power created by inverters.
> How is that done?
> I would have thought M/G set.
> 
> Guess I'm getting too old for new technology.


Same way a VFD produces a 3 phase output to drive a motor. It uses three sets of switches (IGBT's, a type of semiconductor device). One switch goes from each of the phase outputs to the positive DC bus, the other goes from each phase output to the negative DC bus. The switches are turned on and off in the proper sequence. That's that. Mostly. It's a bit more complicated, since you actually have to turn them on and off repeatedly during each cycle to approximate a sine wave.


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## shieldcracker (Sep 14, 2009)

Del sol are these inverters grounded elsewhere?


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## Gilligone (Dec 12, 2009)

Delsol,
What did you find out? Were these Satcon inverters? If yes, are they "Gen II" (current versions)?

I know of two other cases where this has happened. Both cases involved an inappropriately specd Wye/Wye tranny. Should have been Wye/Delta. 

I'm with MDShunk & bobelectric... "Are you sure?" and "I wired it the way it said on the drawings"

What was the fix?


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## BuzzKill (Oct 27, 2008)

MDShunk said:


> :laughing:
> 
> Along the lines of an RFI, I'd like to propose a new form to send to engineers. An AYS form, for "are you sure" ...that you really want it done this way.


That would be nice!


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