Power Capacitor

Power capacitors become relevant when power factor fines take effect in the monthly statement and transformer loading appears much greater than the actual kW load. After determining the load profile, checking for harmonics present and factoring in the required kvar step size, we then install power capacitors. Fixed capacitors are applied to loads that remain constant whereas, for loads with variations in demand, capacitor banks are separated into many steps and managed using Automatic Power Factor Correction devices to provide accurate correction for changing loads.

Capacitor ratings are based on the system voltage and temperature rise within the electrical enclosure. Application of detuning reactors will also be determined whenever Variable Frequency Drive panels or any other nonlinear load(s) are used, since using standard direct connect for these applications can result in shortened capacitor life. Capacitor duty contactors with precharging devices are used to control inrush current to prevent contact weld. The capacitor discharge resistors are checked to confirm the protection circuit has enough time to allow the residual voltage level to be at or below an acceptable safety criteria prior to the next switch cycle.

The mounting of the equipment creates an adequate airflow space between the individual units; because of the continual output of kvar, the equipment generates heat. The busbar and cable sizes are sized based on full reactive current. Prior to integration, each unit undergoes capacitance measurements, checks for insulation resistance, and checks to ensure that all terminal connections are snug.

In United States power systems, these power capacitors are used to support a stable power factor while reducing reactive current within the overall system. They also provide a means for supporting the transformer and cable capacities without overheating or causing voltage fluctuations.