Compensation capacitors supply local reactive power in AC systems to offset inductive loads, improving power factor and stabilizing voltage—an IEC-mandated technical and economic requirement. Available as fixed (for steady loads) or automatic (dynamic adjustment, reduced overcompensation risk) units, they need IEC-compliant protection against overcurrent/voltage/temperature. They do not affect active power; distributed compensation may outperform centralized types in some cases.

Cylindrical capacitors are widely used in low-voltage industrial power systems due to their mechanical robustness, excellent thermal performance, and easy integration into IEC-standard capacitor banks. Structurally, they adopt wound metallized polypropylene film with self-healing features and overpressure protection, ensuring safe operation. Electrically optimized for fundamental frequency, they suit power factor correction, motor control, and renewable energy systems but require detuning reactors in harmonic-rich environments. Outdoor use needs proper enclosures, and pre-installation harmonic studies are recommended per IEC guidelines.

Filter capacitors are core components of passive harmonic filters for industrial power systems, working with reactors to divert specific harmonic currents via frequency-selective circuits. Unlike standard shunt capacitors, they endure elevated RMS currents, non-sinusoidal waveforms and high dielectric stress, and are applied in tuned/detuned configurations. Key design considerations include load harmonic spectrum and thermal conditions, with wide uses in manufacturing plants, data centers, etc. They differ from active filters and cannot operate alone.

Shunt capacitors are widely used for power factor correction in AC systems. By supplying capacitive reactive power to offset inductive loads’ lagging current, they cut line current, boost voltage stability, and enhance equipment efficiency. Available in individual, group or centralized configurations with automatic switching, they carry risks like overcompensation and resonance, which require adherence to IEC guidelines for mitigation.

This paper compares shunt capacitors and filter capacitors in power systems. Shunt capacitors, paralleled to grids, optimize power factor by supplying reactive power, suitable for low-THD steady systems. Filter capacitors, combined with reactors in harmonic-rich environments, suppress harmonics while compensating reactive power, preventing resonance. Selection depends on grid harmonic profiles, per IEC standards, to balance power quality and system reliability.