Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
(OP)
We are working at a plant right now, it's probably 50+ years old that has two main substations. One is fed by a wye wye 12470V - 480V, the other wye - delta, same voltages. They aren't tied together via a tie breaker. I've never seen this before just wondered what's the advantage of this? And why would they be different? They've had some issues, and are considering changing things out in order to increase reliability. Any suggestions?






RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
There was a period when these systems were converted to wye:delta to increase capacity.
This was followed by a period of issues with wye:delta systems.
The wye:wye system avoids the problems associated with wye:delta systems.
That is; Grounded or four wire wye:delta, circulating currents and backfeeds into primary system faults.
Floating wye:delta, switching transient overvoltages.
Bill
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"Why not the best?"
Jimmy Carter
RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
So when that lamp glowed bright, we would get on the radio and ask who in the plant was having problems or seeing smoke, or if nobody responded we would jump in golf carts and drive around like keystone cops looking for it. Good times...
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
A lamp on an MCC went out one day. The foreman sent a good young electrician to find the problem.
Two and a half days later he stomped into the shop and threw his tool belt on the bench.
The foremen asked;
"Found the trouble yet?"
"Yes, d____ it I found it!"
"What was the problem?"
"The d___ light bulb was burnt out!"
My first thought;
"Thank God it was him and not me!"
I have also worked in plants that used a resistance grounded wye so as to be able to continue running with a ground fault on one phase.
Bill
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"Why not the best?"
Jimmy Carter
RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
I have always thought it scary that someone could get hurt or killed in the field without anyone doing anything incorrectly.
RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
RE: Is there any advantage to ungrounded wye wye power systems? Ungrounded Wye delta?
A wye system may be impedance grounded with a high enough impedance that the system may operate with a ground on one phase.
The impedance may limit the ground fault current to a value that does no damage.
The problem is when you have an arcing ground fault.
A persistent arc of even a few Amps may eventually do serious damage.
Bill
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"Why not the best?"
Jimmy Carter