Transformer expert required :)

[Mou]

Hi guys,

I've Y-Y MV( 13.8KV sec /480V Pri) transformer and we connecting it to 3 wires BUS( 13.8KV) , So I've three options for the neutral connection on high side winding:
1- No connection ( floating)
2- solidly ground it
3- design ground reactor.

1st of all the three wires BUS is grounded through the up stream transformer reactor. in other word the upstream transformer is D-Y (115KV P/ 13.8KV sec) with the connection the Y to ground through reactor and the run the three wires only to the factory BUS.

So which one of the option will best work with fault current and best design practice?

 

[tortuga]

Hi guys,

I've Y-Y MV( 13.8KV sec /480V Pri) transformer

So your going from a 480 primary to 13.8 secondary?
No surely you meant 13.8 primary.
What do you mean by BUS is that just that busbar?
I would tend to rule out option 1.

 

[Mou]

So your going from a 480 primary to 13.8 secondary?
No surely you meant 13.8 primary.
What do you mean by BUS is that just that busbar?
I would tend to rule out option 1.

Its step up transformer from 480 to 13.8KV. the Bus is 13.8KV MV gear 3 wires .

 

[big john]

You float the 480V primary because regrounding will put neutral current on your equipment ground.

Ground your 13.8kV secondary to stabilize system voltage and help clear faults. If you have the option, use a HRG system to reduce fault current.

 

[Smart $]

You float the 480V primary because regrounding will put neutral current on your equipment ground.

Ground your 13.8kV secondary to stabilize system voltage and help clear faults. If you have the option, use a HRG system to reduce fault current.

If I'm not mistaken, this xfmr is the same one as in the thread PV Transformer connection. I believe you will revise your assessment once you review the information contained in that thread, especially the one line diagram (zooming in required; xfmr discussed here not depicted).

 

[ggunn]

You float the 480V primary because regrounding will put neutral current on your equipment ground.

I don't think that is an option; the inverter(s) he is putting on the 480 side probably need(s) a grounded neutral to operate.