Dear Mandeep,

You are unclear if you speak of acoustic noise or electric noise!

I assume you want to address the acoustic noise: whatever you do, by essence the core of the transformer will "pulsate" at 50Hz harmonics due to magnetostriction, proportional to the intensity (load). This volume change is transmitted with almost no attenuation to the transformer enclosure by the cooling and insulating oil. Because it is driven by the squared intensity, which is far from a nice sinusoid, it contains all harmonics of 25Hz. You can't do anything, it is basic electromagnetism physics.

The only noise reduction measures that would work have to reduce the noise radiation efficiency of the transformer casing; they have to be balanced by the need of air cooling by natural convection, and the two requirements are often antagonist. If you can ensure the proper cooling by another mean, it becomes easier to streamline the casing shape and encapsulate it, in order to reduce this noise radiation efficiency! You must also address all the structural couplings between the transformer and its environment (isolators, flexible cabling etc.) to avoid structural paths later creating noise... It is a well known problem and you should be able to find many publications on the web to get precise examples.

Electric noise suppression is a distinct issue however well documented too. It is easy to implement at the KW scale (see for example https://electrical-engineering-portal.com/isolation-transformer-suppress-transients-noise) (but at the massive MW power distribution grid technologies it turns to a far greater challenge - I believe this is not your case!)

Noise in transformers could be minimized by running it at rated full load. The magnetising current the main cause to produce noise of core stamping petting and would increased with time due to the aging effect on insulation and grips on stamping. Could be reduced by maintenance and varnishing…..

Here are some best practices for reducing noise in an HV transformer:

• Use acoustic dampening material. Acoustic dampening material can be used to absorb sound waves and reduce noise levels. This material can be applied to the transformer's housing or to the surrounding walls and floors.
• Use vibration dampers. Vibration dampers can be used to reduce vibrations that can cause noise. These dampers can be installed on the transformer's base or on the surrounding structures.
• Use sound barriers. Sound barriers can be used to block sound waves from reaching sensitive areas. These barriers can be made of a variety of materials, including concrete, brick, and wood.
• Use noise-canceling technology. Noise-canceling technology can be used to create sound waves that cancel out the noise from the transformer. This technology can be used in conjunction with other methods to reduce noise levels.

The best method for reducing noise in a HV transformer will depend on the specific circumstances. If the transformer is located in a sensitive area, such as a hospital or a school, it may be necessary to use multiple methods to reduce noise levels.

Here are some additional tips for reducing noise in a HV transformer:

• Keep the transformer clean. Dirt and debris can build up on the transformer and cause noise. Regularly cleaning the transformer can help to reduce noise levels.
• Inspect the transformer regularly. Regularly inspecting the transformer for any damage can help to prevent noise problems. If any damage is found, it should be repaired as soon as possible.
• Use the proper equipment. When working on a HV transformer, it is important to use the proper equipment. This includes using safety glasses, gloves, and a hard hat.

By following these tips, you can help to reduce noise levels from a HV transformer and create a more peaceful environment. Specifically for your situation, you may want to consider the following:

• Use a higher-quality epoxy. The quality of the epoxy used to mold the transformer can have a significant impact on noise levels. Using a higher quality epoxy can help to reduce noise levels.
• Use a thicker epoxy layer. A thicker epoxy layer can help to reduce noise levels by providing more insulation between the transformer's components.
• Use a sound barrier around the transformer. A sound barrier can be used to block sound waves from reaching sensitive areas. This can be a particularly effective way to reduce noise levels if the transformer is located in a sensitive area.

By following these tips, you can help to reduce noise levels from your HV transformer.