Understanding how to troubleshoot common issues with harmonic filters is essential for maintaining power quality and minimising downtime. In this article, we’ll explore the most frequent issues that arise with harmonic filters and the troubleshooting steps we would take to address them effectively.

Ineffective Harmonic Reduction:

Issue: Despite the presence of a harmonic filter, harmonic distortion levels remain high, affecting the performance of electrical equipment.

Troubleshooting Steps:

  1. Verify that the network conditions or load profile/characteristics  haven’t changed
  2. Inspect the filter components for damage or deterioration that could impair their effectiveness.
  3. Use power quality meters to measure harmonic levels and identify any discrepancies between expected and actual performance.
  4. Consider upgrading to a more advanced or larger capacity harmonic filter, if necessary, or addition of new filtering unit.


Issue: The harmonic filter components are overheating, leading to reduced efficiency and potential damage.

Troubleshooting Steps:

  1. Check for airflow obstructions around the filter enclosure, such as dust buildup or blocked vents, and clean as necessary.
  2. Verify that the filter is not overloaded and is operating within its rated capacity.
  3. Inspect the cooling system to ensure it is functioning correctly.
  4. Monitor ambient temperature conditions and consider installing additional cooling or ventilation, if needed.
  5. Liaise with the manufacturer/supplier to replace any faulty or worn-out components contributing to overheating if necessary.

Voltage Resonance:

Issue: Resonance occurs between the harmonic filter and the electrical system, leading to voltage instability and potential equipment damage.

Troubleshooting Steps:

  1. Conduct a thorough analysis of the system’s impedance characteristics to identify potential resonance frequencies.
  2. If there are PFCs or passive filters within the network, verify operation of the filter while those components are removed from circuit (switched off/isolated)
  3. Adjust the tuning parameters of the harmonic filter to shift resonance frequencies away from critical points.
  4. Install damping or detuning devices, such as resistors or reactors, to suppress resonance and stabilise voltage levels.
  5. Consider redesigning the harmonic filter configuration or integrating additional filtering techniques to mitigate resonance effects.
  6. Consult with a qualified engineer or specialist if resonance issues persist, as they may require advanced diagnostic tools and expertise.

Troubleshooting common issues with harmonic filters requires a systematic approach and a thorough understanding of electrical systems and power quality principles. Through site surveys, monitoring systems, and power system modelling we can effectively diagnose and resolve problems with harmonic filters, ensuring reliable operation and optimal performance of your electrical system. Contact our power quality experts today for further advice.

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