Vibration Analysis of transformer
Vibration analysis by itself cannot predict many faults associated with transformers, but it is another useful tool to help determine transformer condition. Vibration can result from loose transformer core segments, loose windings, shield problems, loose parts, or bad bearings on oil cooling pumps or fans. Exercise extreme care in evaluating the source of vibration. Many times, a loose panel cover, door, or bolts/screws lying in control panels, or loose on the outside have been misdiagnosed as problems inside the tank. There are several instruments available from various manufacturers, and the technology is advancing quickly. Every transformer is different; therefore, to detect this, baseline vibration tests should be run and data recorded for comparison with future tests.
9.6.2 Vibration Analysis of transformer Process
For a normal transformer in good condition, vibration data is normally two times line frequency (120 Hz) and also appears as multiples of two times line frequency; that is, four times 60 (240 Hz), six times 60 (360 Hz), etc. The 120 Hz is always the largest and has an amplitude of less than 0.5 inch per second (ips) and greater than 0.1 ips. The next peak of interest is the four times line frequency or 240 Hz. The amplitude of this peak should not exceed 0.5 ips. None of the remaining harmonic peaks should exceed 0.15 ips in amplitude. See EPRI’s Proceedings: Substation Equipment Diagnostics, Conference IX  section on “Vibration Analysis.”