corner grounded Delta system
corner grounded Delta system
(OP)
We have an old system in our plant that is the grounded B phase or the corner grounded delta. Whichever you want to call it. What we have is 4160V feeding 4 step down transformers that step it down to 230V Grounded B. When you open the secondary side of the 500kva transformers the center phase has a 500mcm bare copper jumper from it to the can of the transformer. My quesion is how does this phase just not short out as in any other system if you took it to ground. any thoughts, Thanks






RE: corner grounded Delta system
I am sure someone will add to this or correct my thinking if I am wrong. And it is very possible that I am way off.
RE: corner grounded Delta system
With some (mostly older)generators, the connections of the two single phase windings can be parallel 120V, series 240V or center tapped series (120/240). With the parallel 120V circuits, one end is selected and becomes the "neutral" and referenced to ground while the other is the "line" at 120V above neutral. The same could be done with the 240 series if desired to have 240 line-ground instead of the ususal 240 line-line, but if the center of the series windings is already grounded (120/240 connection), you cannot ground another point without sparks!
RE: corner grounded Delta system
Because there is no return path back to the source since the circuit is incomplete. Therefore, no short circuit current will flow.
Please notice that the corner grounded phase is a ground potential. Therefore, any other phase to ground fault will cause a phase-to-ground-to-phase fault.
RE: corner grounded Delta system
what is the advantage with corner grounded delta ?
* If you have never succeeded in anything in first attempt, skydiving isn't for you. *
RE: corner grounded Delta system
RE: corner grounded Delta system
RE: corner grounded Delta system
If you use a grounded delta system, one phase to ground path and your sunk.
HP
RE: corner grounded Delta system
At the time these systems were used routinely, ungrounded delta systems were very common. Grounded systems have many advantages (discussed here previously). The cheapest way to obtain a grounded system for an ungrounded delta was to ground one phase.
RE: corner grounded Delta system
* Homer Wisdom - "Operator, Give me the number for 911" *
RE: corner grounded Delta system
a) From the economics point of view, the corner grounded delta save in wiring, hardware and installation cost comparing with respect 4 wires grounded systems.
b) During normal operation conditions, grounding a corner stabilize all the voltages to earth providing better voltage regulation to the system.
c) During transient conditions created by lightning, line surges, or unintentional contact with higher voltage lines, the overvoltage is limited to lower values. This translates in better chance for longer life of electrical equipment insulation.
Beware that better solutions are available for new installation