How do harmonics affect capacitors?
The harmonic characteristics of the supply matter as much as reactive power when selecting a capacitor bank. Two solutions with the same kvar rating may behave differently in different installations.
What changes with frequency?
For an ideal capacitor, Xc = 1 / (2πfC). Reactance decreases as frequency increases. Harmonic voltage components can produce additional capacitor current and thermal stress.
Why resonance matters
The capacitor bank and the network’s inductive elements can resonate. If their natural frequency approaches an existing harmonic, current or voltage at that frequency may be amplified. Capacitors do not generate harmonics, but can change the network’s response to them.
What do detuning reactors do?
Appropriately selected series reactors change the resonance behavior and help limit harmonic effects on capacitors. They are not a universal solution that eliminates every harmonic. Selection requires harmonic-spectrum and network data.
Do not choose reactor percentage or capacitor voltage from a generic table alone. Site measurements and manufacturer coordination are needed.
Schneider Electric — Risk of resonance due to power-system harmonics ↗
Schneider Electric — Possible solutions for power-system harmonics ↗
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