The reactance of a generator changes during a fault. There are three stages, subtransient, transient and synchronous. For most faults, subtransient reactance is used because it produces the highest fault current, i.e worst case scenario.
With regards to saturated and unsaturated, I believe this...
Can someone please summarise the advantages of using hydrogen as a cooling medium for high speed turbines, and perhaps give an indication of any efficiency differences between hydrogen cooled units and water/forced air cooled units?
Thanks