Thanks Laplacian, you are correct. Checking the phasor values on the Multilin is the best way to trouble shoot and confirmed the phase rotation was actually ACB not ABC as originally set. Switching corrected the problem. Now onto the next challenge.......
Unfortunately, I am not on site anymore so my information is limited.
I believe the currents were relatively balanced (less than 1%). I will check some more settings and try changing the system phase sequence to ACB from ABC to see the effect.
Thanks for all the responses thus far.
I have three SR469's each feeding identical motors (250 HP, 575V). The current readings appear correct and visual inspection of the CT's appear correct (polarity & wiring - although wiring has not been confirmed by electrically tracing).
All three show current unbalance readings in the...
OK, thanks all for your responses. I believe the correct way to analyse this situation is as an unbalanced three phase star connected load (without ground connection). The two balanced phases have an impedance due to the system's capactiance to ground. The third phase has an impedance...
There is a small flow of current depending on the the system capacitance and voltage (sometimes refered to as the system charging current). (For 13 kV the charging current can be in the 5A range)
For a solid ground fault the current is in the order of twice the charging current but I am unsure...
I am trying to calculate the ground fault current (do to the system capacitance) of a single phase to ground fault through a finite resistance ground fault connection on an ungrounded delta system.
Does anyone know the method? I believe I have the formula's for a simple solid ground fault but...
