In low-voltage power supply and distribution system design, reactive power compensation capacitor banks and active harmonic filter banks are commonly used devices to improve the operating conditions of the power grid. The installation sequence of these two on the busbar directly affects the harmonic mitigation effect, the reactive power compensation operation status, and the service life of the electrical equipment. Many projects place the filter bank behind the capacitor bank; why is this arrangement chosen?

  Capacitor banks are mainly used for reactive power compensation in power grids. By switching capacitor banks on and off, they provide capacitive reactive power to the system to offset the reactive power consumption generated by various inductive loads, thereby improving the power factor, reducing active power losses in transmission lines, and optimizing the overall operation of the power grid.

  The main function of a active harmonic filter cabinet is to filter out various harmonics present in the power grid. Harmonic components are generated during the operation of nonlinear loads, which can easily cause voltage and current waveform distortion, leading to phenomena such as equipment overheating, insulation aging, and control circuit malfunctions. Filter cabinets can absorb and suppress these harmonics, maintaining the stability of the power grid waveform.

  Placing the filter cabinet behind the capacitor bank allows for the mitigation of both background harmonics and harmonics generated by capacitor compensation. During switching and adjustment, the capacitor bank generates harmonics, and the capacitors' impedance characteristics make them prone to coupling with existing grid harmonics. Rear-mounting the filter cabinet ensures unified filtering of both existing grid harmonics and those generated during capacitor operation, providing complete harmonic mitigation coverage and improving overall filtering effectiveness.

  In addition, this arrangement can reduce the continuous impact of harmonics on capacitors. The capacitor bank is directly connected to the distribution bus for reactive power regulation, and a filter device is added at the back end to process the current and harmonics flowing through the capacitor circuit. This weakens the circulating current formed by harmonics inside the capacitor, avoids long-term harmonic overcurrent that leads to excessively high capacitor temperature rise and accelerated insulation aging, reduces the probability of capacitor bulging, breakdown and other faults, and extends the service life of the equipment.

  The rear-mounted filter cabinet layout can also weaken the mutual interference between reactive power switching and harmonic disturbances, stabilize bus voltage and current fluctuations, reduce the impact on transformers, incoming switches and outgoing equipment of each circuit, and allow the entire low-voltage power distribution system to operate under safe and stable conditions, which can also meet the actual needs of on-site electrical installation and subsequent operation and maintenance.