Zusammenfassung
The reliable operation of power transformers is an essential factor for
the high availability of electric energy. Reliability demands can be
enforced using condition based asset management which relies on
different diagnosis measurements and continuous monitoring. This
contribution determines the abilities of asset monitoring by regarding
transformers' mechanical oscillations during operation. The physical
origins of oscillation sources are introduced as well as the common
measurement technique using accelerometers. The contribution evaluates
the method's principle diagnostic abilities by correlating the actual
mechanical status of an active part and resulting mechanical vibrations
in a laboratory setup. The practical usability is determined by
long-term comparison of measurements on different power transformers in
service. Several influencing factors are evaluated: the sensor position,
the changing transformer's load and operating temperature during service
as well as the position of the on-load tap changer. Additionally,
mechanical oscillations are used to determine the influence of
superimposed, undesirable DC components on 3-limb power transformers
originated by coupling between nearby AC and HVDC lines.
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