Figure 13. (Top) Voltage distribution as a function of time as the voltage rises from 0 to 135 kV. Since the 1 s voltage rise time is about 30 times the 35 ms dielectric time constant, the effect of the capacitive grading during the voltage rise is relatively small as a result of dielectric relaxation during the voltage rise. (Bottom) The electric field distribution as a function of time starting from completion of the voltage rise at 1 s. The system continues to relax until it reaches resistive grading within about 3 s (2 s after completion of the voltage rise) and remains resistively graded until the voltage starts to decrease