When capacitors are switched on, the initial current surge
causes a notch in the voltage (a sub-cycle voltage drop). As
the voltage rises back to its nominal peak, it may overshoot to
levels that can reach and even exceed 400% of nominal
values. Steady-state condition is reached after a period of
voltage oscillation. The fiequency of this transient is rather
low (tends to range between 200 Hz and 1.5 kHz).
The magnitude, duration, and frequency of this oscillatory
transient will depend on many factors such as load damping,
system inductance, and possible resonant conditions in the
system, etc. If the customer circuit tuned at or near the
switching transient oscillation fiequency, it will be amplified
causing problems to customers at the receiving end. Time
domain simulation, shown in Figures 28~3, shows the
transient over voltages aid the low frequency oscillation at
the customer low voltage end when switching-in the utility
capacitor. In Figure 4 the switching over voltages with
different capacitor switching is illustrated. In this system, it
can be seen that peak voltage magnitude can reach up to 2.5