HARMONICS AND TRANSIENT OVERVOLTAGES DUE TO CAPACITOR SWITCHING

This paper presents a study of the steady state and transient effects of power factor correction capacitors on the utility and on the custom er. In the presence of harmonic producing loads, capacitors used for p ower factor correction can cause parallel or series resonance problems which tend to increase the total harmonic distortion (THD) of the vol tage and current waveforms. The cases studied in this paper consider t he addition of a power factor correction capacitor, in the presence of downstream harmonic loads and at the harmonic load site. In both case s the resonance created by the addition of the capacitor caused the ha rmonic distortion of the voltage and current waveforms to increase. An other problem is transient overvoltages created by snitching the capac itor. The overvoltage at the customer bus created by switching the cap acitor can be harmful to,sensitive electronics equipment. A case study is reported where the operation of semiconductor controlled motor dri ve is effected by transient overvoltages. The first section of this pa per looks at the steady-state concerns associated with the application of power factor correction capacitors in the presence of harmonic loa ds and unbalance. The latter section of this paper discusses the trans ient problems associated with the switching of power factor correction capacitors.