Power Factor Correction

When a power factor problem has been identified, the traditional solution has been to install capacitor banks. This approach worked in the past, but it has become more difficult to apply capacitors in a system containing both high harmonic content and sensitive loads that cannot tolerate voltage transients.
The presence of harmonic current in a system typically causes power capacitor ratings to be exceeded. Capacitors will absorb harmonics as frequency increases and their impedance decreases. The effect is overheating and increased stress, which results in premature failure. Capacitors will resonate with the system inductance. This can cause high voltage spikes and current up to 10 times the normal levels. Fuses will blow and the capacitors will be stressed to total failure or may even burst.
A power factor controller can be used to regulate the addition or removal of numerous small banks of capacitors to meet the objective of closely approaching unity. The switching performed by the controller to accomplish the mission also creates voltage transients which cause overvoltage to the load. This can damage solid state equipment such as variable frequency drives.
If the capacitor system does not use a power factor controller, synchronous motor loads could present an overabundance of reactive power. This can lead to an overvoltage condition in the plant that results in a leading power factor during light load periods. This creates serious problems for equipment used in the plant and also for the local electric utility. The resulting overvoltage causes dangerous instability. The presence of harmonic current in a system typically causes power capacitor ratings to be exceeded.
Capacitors will absorb harmonics as their impedance decreases and frequency increases. The effect is overheating and increased stress, which results in premature failure.
Capacitor will resonate with the stem impedance this can cause high voltage spikes and current up to 10 times the normal levels. Fuses will blow and the capacitors will be stressed to total failure or may even burst.
The switching of the capacitor banks in and out creates voltage transients. These transients cause overvoltage to the load and can damage solid state equipment. Such as variable frequency drives.
Current harmonic filters must be designed protect the capacitor bank. This protection will be effective only as long as the original loads (those in place when the study was conducted) remain in place. If you change out or add new equipment. At that point, shutting the capacitor bank down may be necessary to prevent resonance.
Introducing capacitor banks into a harmonic rich environment also introduces an ongoing battle to reduce harmonics. Condenser operation is unaffected by current harmonics and does not create any system problems.