Operating Condition of the EUT
The flicker standard states that the EUT (Equipment Under Test) has to be operated during the test in a way which is the worst case state with respect to flicker.
If the EUT is operated in a (relatively) constant fashion during the whole test, Plt = Pst will result. If this state is is feasible and realistic this means Pst has to fulfill the limits for Plt (which are lower!)
A purely analytical calculation of Pst is almost impossible, so we have developed FlickerSim and made it available open-source.
However, formulas for the first estimation of the expected Pst values are given in the standard :
n = number of load changes in the observation interval
Tp = duration of the observation interval in seconds
F = shape factor (1 for step-wise voltage changes)
d = relative voltage change relative dU / U
In  there are also shape factors for different curve forms.