What is harmonic resonance?
A. When a capacitor bank is added to a power system, it is effectively connected in parallel with the system’s impedance, which is primarily inductive. As far as the harmonic source is concerned, it sees a capacitor in parallel with an inductor. Since the capacitive and inductive reactance are frequency dependent, there is a frequency at which these two parameters will be equal. This frequency is called the system’s natural resonant frequency. At this frequency, the system’s impedance appears to the harmonic source to be very large; therefore, a harmonic current at the resonant frequency flowing through this impedance will result in a very large harmonic voltage.
