Why should you worry about your capacitors?

CONDIS® high voltage capacitors are installed in or nearby high voltage switchgears and instrument transformers, in nearly every substation all over the world. These are key elements for a safe and well performing electrical network. In the rare case of a capacitor failure, the surrounding (and often expensive) equipment may suffer severe damage.
To guarantee the reliability of our components, we suggest a regular maintenance plan and offer services accordingly. This allows you to avoid unexpected outages, manage your risks and forecast your expenses.

What can be done by you (on-site)?

On-line diagnostics

  • Measure the capacitor’s temperature by infrared thermal radiation. Basic approach of monitoring. Helps to quickly control the capacitor’s behavior showing its general condition.
  • Visual inspection

Frequency: Every time you assess your substation equipment.

 Off-line diagnostics

  • Measure the capacitance and the tangent delta at 10 kV. Contact our services department for an offer to interpret the measured values.
  • Cleaning. Deposits (i.e. pollution) degrade a capacitor’s performance.

Frequency: Whenever the associated circuit breaker’s maintenance is performed.

What can CONDIS do for you (off-site)?


Provide us with your capacitance and tangent delta measurements, your capacitor type, serial number and other data (request our check-list and we can offer our services to process the results and advise on the capacitor’s condition.

Testing in a high voltage laboratory

The routine test is the most accurate way to assess a capacitor’s condition and prevent potential failures. The test needs to be conducted in a high voltage laboratory.

Frequency: We recommend thorough testing approx. every 20 years. See CONDIS’ HV Capacitors Life Cycle Policy for details. The frequency is subject to a capacitor’s application. Each case is evaluated individually.

Repairs & recalibration

Depending on the results of the above mentioned tests and activities, we can proceed to repair or replace spare parts and recalibrate the capacitor.


What can happen if I don’t worry about my capacitors?

  • Damaged insulator

Cracked or damaged sheds on the insulator or damages to the insulator itself will modify the creepage distance and thereby increase the risk of flashover.

  • Dielectric Breakdown

The dielectric’s ageing is a chemical process. This can destroy molecule connections which may reduce the dielectric’s voltage behavior.

  • Corrosion & Leaks

The dielectric fluid undergoes temperature variations which alter a capacitor’s internal pressure. Should this cause leakage, it may accelerate the dielectric’s ageing process and miscellaneous elements may modify its voltage behavior.

Source: CIGRE TB368

However, despite the above arguments, as capacitors are and remain passive elements, regardless of their state, these never represent a danger.


For more information about CONDIS’ product lifecycle policy and advisory services, do not hesitate to get in touch with us now.

We would love to hear from you!