The doctor’s stethoscope is a diagnostic tool for evaluating acoustic noise. TAPSCAN® VAM – the new vibroacoustics service from Maschinenfabrik Reinhausen (MR) – has a very similar function.

With people, the stethoscope evaluates the state of health and with transformers it evaluates the state of the on-load tapchanger (OLTC), which is responsible for regulating power transformers. This complex electro-mechanical component is of critical importance for operators, since it is indispensable for supplying energy free of malfunctions and interruptions.

VIBROACOUSTICS ARE IDEAL FOR THE JOB
MR is the world market leader in regulating power transformers using on-load tap-changers and, in addition to offering numerous innovative transformer-related products, also provides comprehensive asset management solutions. Optimising asset management is becoming increasingly important as the requirements placed on transformer service lives continue to increase the world over. Evaluating the state of on-load tap-changers is therefore indispensable and vibroacoustics are ideal for the job. The benefits include quick, reliable and detailed evaluations without needing to disconnect the transformer from the network.

HOW DOES THE VIBROACOUSTIC MEASUREMENT WORK?
Each on-load tap-changer has a specific profile – its ‘heartbeat,’ so to speak – which is recorded and transmitted using acceleration sensors. The sensors are attached to suitable measuring points depending on the design of the transformer. They are attached with either screw or cap nut adapters or using an adapter glued or magnetically attached to the transformer tank. The best possible connection to the tapchanger is usually obtained on the tap-changer cover. The sensors are then connected to the measuring device via a measuring cable. Additionally, a self-powered current clamp is attached to the motor-drive unit to trigger the measurement. This is used to determine when the motor is running or the OLTC is being driven and when the next tapchange operation is imminent.

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