A voltage higher than 110 per cent of rated is undesirable. The over-voltagecondition will decrease the life of the equipment and increase the maintenance costs. The utility isalso affected by customers with low leading power factor because of increased I2R and I2X lossesand the potential for voltage increase in neighboring customers facilities. Harmonics are caused by non-linear loads such as variable frequency drives, UPS systems,fluorescent lights, etc. A power system has a natural resonant frequency and the addition ofparallel capacitors will lower the resonant frequency.
Harmonics can cause protective devices to malfunction.
Capacitors can attract harmonics from neighboring customers into the facility. Resonance problems can be avoided by having a harmonic study performed to determine ifharmonic filters are required to correct power factor. If 20 per cent or more of a facility's loads are harmonic generating, a full power quality studyshould be performed by an experienced consultant. There are various products on the market to suppress these disturbances. Capacitor Testing Capacitors should have a functional test upon installation to determine if the capacitor is operatingat its rated kvar.