Interesting fault results!? Any explanation?

[wonderchi]

Hi,

I have performed fault anaylsis using SKM, the results obtained is quite interesting...

The biggest initial symmetrical current is LLG 19.5kA followed closely by SLG 19.36kA

However the highest asymmetrical current is SLG 47.5kA and 46.6kA for LLG fault. Why is this reverse?

Dont know why? Can any one help

Thanks

 

[DanDel]

Are you asking why the asymmetrical currents are higher than the symmetrical (which is typical), or why the asymmetrical SLG is higher than the LLG?

 

[jghrist]

The ratio of asymmetrical to symmetrical depends on the X/R ratio of the fault impedance. This ratio is different for Z1, Z2, and Z0. Z0 has more influence in the SLG fault than in the LLG fault. The Z0 may be dominated by a large power transormer that has a high X/R ratio compared to the system impedance.