Nope. Neither dry nor oil-filled transformers are supposed to be noisy by nature. When you hear noise it is often the result of something from power factor conditions, harmonics, core looseness, coil looseness, overload, or other condition. Some smaller level of sound is reasonable, however, something such as the following is abnormal.
ESA data on the transformer and analysis using the method outlined in Analyzing Transformer Sound with a Phone – Poor Man’s Analysis – MotorDocAI were performed:
The ‘Analyzing Transformer’ article code was used to perform a decibel based FFT analysis of the sound and compared to IEEE Standard C57.136-2000, “IEEE Guide for Sound Level Abatement and Determination for Liquid-Immersed Power Transformers and Shunt Reactors” which identified this pattern as related to high harmonic conditions.
In addition to the power harmonics, ground and neutral circuit harmonics were also present. The transformer was lightly loaded at 248/1500 kVA and a load of 227 kW. The total power, ground and neutral losses were found at 33kW which resulted in an approximately greater than 289,080 kWh per year loss. This calculates out to ~205 Tonnes CO2 per year improvement in plant emissions if corrected. The harmonic conditions were traced (quickly) with EMPATH to several old VFDs that did not have filters installed.
Total time for detection to findings with an inexperienced EMPATH user was <45 minutes.
