Zero sequence current & impedance for an all delta network 2

[TS Liew]

Dear friends,
If a delta generator/network (without neutral) experience a solid line to earth fault. What will the fault current be? How can it be calculated/simulated?

TS Liew (Electrical testing, Commissioning, Power system studies)

 

[davidbeach]

You'll have to know what all the parasitic capacitances are. What gets call an ungrounded system is actually a capacitively grounded system and the currents all depend on those capacitances. Currents will be small. In many instances zero current is a sufficient approximation.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[TS Liew]

Hi Guys, thank you for your valuable input. Assuming negligible capacitance. If the delta network experience a solid low resistance (Zn) fault to ground. Do you recon the fault current from line to ground to be Vfault/Zn? Based on the zero seq equivalent network for delta we see that the zero seq Zo is trapped in the delta winding thus I wonder what the fault current on the line would be. Would it be negligible too when the ground do not provide any path for the "fault current" to flow? Some kind off discharge?

TS Liew (Electrical testing, Commissioning, Power system studies)

 

[RRaghunath]

If you say negligible capacitance, the fault current will be nil as there is no closed loop for earth fault currents to circulate.
The zero sequence impedance thus have to be theoretically infinity. It is windings to tank and cable capacitance that could allow some current to circulate, that's it.

 

[7anoter4]

Personally, I have not had such a situation, but it is possible. Here the line impedance can be entered.

 

[jghrist]

What you have shown is a phase-phase fault because you have two connections to ground on different phases, which becomes a connection between phases.

 

[7anoter4]

Of course, but through grounding resistance.

 

[TS Liew]

Thank you guys for the valuable info. They have been really helpful.

TS Liew (Electrical testing, Commissioning, Power system studies)

 

[FacEngrPE]

What you illustrated is corner grounded delta.