Withstand current = also referred to as making currents
Interrupting duties = also referred to as breaking short-circuit duties.
AC Decrement = a symmetrical short-circuit current that has a time-varying change from
peak to peak during the fault (i.e. the peak to peak distance varies with
time)
Near to generator
short-circuits = fault currents which have an AC decrement
Far from generator
short-circuits = fault currents exhibiting no AC decrement
I k = initial symmetrical short-circuit current at the fault location. If there was
no AC decay, then this current would be constant in that the peak-to-peak
values would not change with time. If there is only DC offset (or decay)
then the peak-to-peak distances remain the same but are not symmetrical
w.r.t. the horizontal axis. With only AC decay, the peak-to-peak distances
remain symmetrical w.r.t. the horizontal axis but they decrease with time to
a steady state value.
Ik = steady state current. This is the conventional symmetrical fault current
when the AC and DC decrements have disappeared. For far from
generator faults, Ik = I k.
IDC = DC Current. The exponentially decaying DC component of the fault
current waveform due to the inductance of the system. It is determined by
the point on the voltage waveform at which the fault occurs. Note this is