Magazine | Issue 1 2024 VAM signals are obtained using magnetically mounted sensors installed on the transformer tank. This connection technique allows the operator to record vibration signals while the transformer remains in service. Consequently, potential changes in the OLTCs’ mechanical integrity can be detected early between maintenance cycles without an outage. By doing this, the VAM can help prioritize individual units for the maintenance schedule. Paweł Molenda is a member of the board and deputy technical director of OBRE Poland. He performs on-site transformer diagnostics and gives technical advice in the transformer and HV equipment fields. He shared the insight he gained when he used the TESTRANO 600 and the VAM1 during his maintenance work on various on-load tap changers. Along with Tomasz Bednarczyk (Application engineer at OMICRON), Pawel and his team conducted several vibro-acoustic measurements to gain more profound knowledge about the OLTCs’ condition. Pawel, what is your typical testing scope for power transformers? Paweł Molenda: The scope and purpose of the test must be tailored to the client. We conduct on-site measurements in the periodic, post-installation, and post-failure measurement fields as part of our measurement activities. This includes testing the insulation state using polarization methods and measuring partial discharge using electric and acoustic methods. To summarize, we offer our clients all types of diagnostic measurements, from basic electrical tests to in-depth condition assessments. We perform measurements according to IEC and IEEE standards and follow customer instructions according to their requirements. «Vibro-acoustic measurements are a good method for initial tap-changer diagnostics that provide a quick and cost- effective initial assessment.» Paweł Molenda, Deputy technical director, OBRE Tomasz Bednarczyk, Application Engineer, OMICRON 7
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