Earth Fault Current Contribution of Dyn transformer with Supplying Motors 1

[EddyWirbelstrom]

A Dyn transformer with solidly earthed star point supplies an induction motor with either delta or unearthed star windings.
Attached Fig. 1 shows PTW32 Ver 9014 Comprehensive results for an earth fault on BUS_0003 with earth fault current contribution from both transformer and motor as expected.
Motor connection could be either star with unearthed star point or delta.
Included is the Comprehensive Short-Circuit text report showing current distribution.

Attached 2 below shows a three-line current distribution for an earth fault on BUS_0003.
Highlighted are the current distribution paths.
Current distribution on the transformer star side and motor is as expected.
PTW does not calculate current circulating in the transformer delta winding.
Using equal ampere-turns in primary and secondary windings I could not calculate the current circulating in the delta windings !
What is the current distribution in the delta windings ?

 

[stevenal]

I0 adjusted by the turns ratio.

 

[7anoter4]

In my opinion, the induction motor does not contribute to the ground fault. However, if the faulted phase potential will be 0 [or close to 0] will be only 2 healthy phases to supply the motor, so the current will be as in case of working in only two phases.
If we neglect the parallel earth impedance and consider phase [2] cables impedance as a half of E conductor impedance, the remaining phase voltage on busbar 003 will be 67%. But, if the E impedance is close to 0 then the phase potential will be 0.

 

[jghrist]

The motor does not contribute zero-sequence current, but positive and negative sequence fault current does flow through the motor.

 

[stevenal]

Did you get an answer? You might post it to see if we agree.