Answer Posted / naresh
when ever there is a fault the current value increases........
the fault is a sub transient condition.....
the reactance offered during first few cycles of faulty
condition the reactance is very less(bcoz in alternator all
three winding's damper,field& armature are connected in
parallel )and the fault current is more..........
after few cycles the current level decreases(bcoz out of
these winding's damper winding cut's off due to lesser time
constant, now field& armature are connected in parallel) due
to increase in reactance this reactance is called transient
reactance.......
after few cycles the field winding cut's off due to lesser
time constant and only the armature winding is present, this
reactance is steady state reactance.........
steady state X > transient X > sub transient X
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