Measurements and Diagnostics

Offline and online measurements

A quick, affordable, and meaningful evaluation of the condition of on-load tap-changers, WITHOUT having to disconnect the transformer from the grid. This is what the new TAPSCAN® VAM service stands for. The vibroacoustic diagnosis process records the specific mechanical noises of an on-load tap-change operation by way of acceleration sensors attached to the transformer. Software programmed in-house and a time-resolved spectral analysis are used to evaluate this data and compare it with reference data of the measured on-load tap-changer type. The know-how and experience from more than 80 years of developing and manufacturing on-load tap-changers are incorporated into a detailed recommendation for action. Vibroacoustics improve the safety and reliability of equipment and minimize risk. Vibroacoustics are a quick and reliable way of producing a qualified and detailed evaluation of the condition of on-load tap-changers in the field.

Another measurement method is the dynamic resistance measurement with TAPSCAN® DRM, which completes evaluation of the OLTC condition. This enables a comprehensive examination of the electrical tap-change operation sequence during every phase, and also determines the override and winding resistance. With TAPSCAN® DRM, a special measurement device is used to record the complete electrical tap-change operation sequence on the switched off transformer. TAPSCAN® DRM detects runtime deviations, mechanical irregularities, and interruptions, and provides an overview of the on-load tap-changer's condition.


Diagnosis of high-voltage bushings
While our technical service team is at your substation, we can also measure the tangent delta or the capacity of your capacitor bushings. In a package together with the on-load tap-changer maintenance, this saves you the costs of switching off your transformer again. Our experts are equipped with the latest measuring instruments. We will provide you with condition assessment independent of the manufacturer and, depending upon the result, recommendations for action. And of course everything in proven MR quality.

If necessary, we can combine a vibroacoustic measurement with a dynamic resistance measurement, thermographic analysis or oil diagnostics. These measurements are recommended, for example, for acceptance tests or commissioning. This delivers a so-called "fingerprint", which enables measurements to be easily compared later on order to derive appropriate measures.


Impressive advantages of offline and online measurements:

  • Quick and reliable, even for sudden measurements
  • Can be used for any on-load tap-changer type from all manufacturers
  • Can be flexibly combined with other measurement methods
  • Graphic display of the results
  • Diagnosis and recommendation for action by experts with decades of experience