Detuned filtering is a reliable and time-tested method to improve the power factor and also mitigating the risk of resonance; this is achieved by shifting the resonance frequency to lower levels, thereby ensuring that no harmonic currents are present.

Single-tuned filter and the detuned reactor is the type of harmonic filter that commonly used to mitigate harmonic distortion. The harmonic filter also has benefit to improve power factor and voltage profile on the system.

When a properly-specified ‘Detuned’ Power Factor Correction system is installed on a network subject to significant levels of Harmonic Distortion, the levels of distortion are reduced. The amount of reduction varies according to the particular characteristics of each system.

If we have a look in formula: Xc = 1 / 2¶fC and XL = 2¶fL which f is frequency of each harmonic order, we will find that if frequency is higher than 5 times, Xc will reduce 5 times and XL will increase 5 times. Now we know that impedance of 6% detuned reactor is 0.205 ohms and inductance value is 0.653 mH (XL = 2¶fL).