Measurement of harmonic impedance on an LV system utilising power capacitor switching and consequent predictions of capacitor induced harmonic distortion

Due to the existence of harmonic voltage distortion in power systems, the connection of power factor correction capacitors can magnify harmonic distortion by resonance with the supply inductance. A common solution to this problem is to install detuning reactance to ensure that the power factor correction unit remains inductive for all the major harmonics present in the system voltage. This paper describes an algorithm to measure system harmonic impedance and harmonic damping, by monitoring the system response to capacitor switching transitions. A prediction of the harmonic voltage distortion due to different levels of capacitance can then be made. The algorithm offers the possibility of an economic software based solution to the problem of harmonic resonance due to power factor correction capacitors.