Diagnostic tests and monitoring help determine the condition of transformers and identify corrective measures to ensure reliable operation and extended service life. As the saying goes, prevention is better than cure.

Transformers are a key component of power systems and hydropower stations. They are usually tailor-made and are very expensive, so it is crucial to know the condition of each unit in order to determine what maintenance is required, or whether replacement should be considered. In view of current delivery times, it is important to anticipate failures by carrying out diagnostics.


Diagnostic tests include the following elements:


    • Insulation measurement
    • Winding resistance measurement
    • Transformation ratio measurement
    • Capacitance and tan δ measurement
    • FDS (Frequency Dielectric Spectroscopy) measurement
    • FRA (Frequency Response Analysis) measurement

    Bushings (terminals)

    • Capacitance and tan δ measurement

    HYDRO has the proven expertise to carry out these diagnostics. Measurements can be taken individually or in groups, in accordance with the relevant standards in force. To complete the diagnostics of a transformer, regular oil analyses are important, which offer a quick indication of the condition of the transformer. This is a service also offered by HYDRO.

    Moreover, HYDRO can carry out diagnostics on dry-type transformers.

      Specific skills

      HYDRO’s engineers:

      • Perform full diagnostics of the transformer in close collaboration with the owner or operator
      • Have over ten years’ experience in the operation and rehabilitation of transformers
      • Leverage their knowledge of the operational business

      Client benefits

      Customers who choose this service benefit from:

      • A personalised service
      • Optimised maintenance and related work
      • A multi-disciplinary partner with expertise in all areas relating to transformers, including the analysis of transformer oil
      • Synergies and feedback from an operational perspective
      • A company that is independent of transformer suppliers

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      HYDRO Exploitation SA
      Rue de l’Industrie 10
      CP 315 - CH-1951 Sion
      Contact us
      HYDRO Exploitation SA
      Rue de l’Industrie 10 CP 750 - CH-1951 Sion +41 (0)27 328 44 11
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