It’s important to take care of new bushings of the transformer for optimum performance. Distribution Transformer India manufacturers bring this guide to assist in testing and maintaining transformer bushings just like a professional does.

Pro tip- Never test a bushing while it is still in its wood shipping crate, or while it is lying on wood or porcelain. Both wood and porcelain don’t insulate and will result in inaccurate readings.

Things to check after 1 month of service and yearly

You should check the external porcelain and find the cracks or contamination (if any). Since there is no perfect insulator, minimum amount of leakage current always present. This leaked current leaks through and along the transformer bushing surface via high voltage conductor to ground. If the transformer bushing has cracks or heavily contaminated, leakage current turns excessive and you could see carbon tracking on the bushing surface.

  • It’s necessary to find oil leakage points. You should check the bushing oil level by viewing the oil level gauge or oil-sight glass.
  • When bushing has gauge with a pointer, check properly as the oil level varies slightly whenever temperature changes.
  • If the pointer stays still, even with wide ambient temperature and load changes, you must check out the gauge at the next outage.
  • Low oil level and external oil leakage indicates that the bolts are loose. You must check the bolts for proper torque and the gasket for compression.
  • Replace the bushing if both torque and compression are accurate

You must know the fact that around 90% of all preventable bushing failures happen due to moisture inside the transformer bushing that can seep through leaky gaskets, seals, or cracks. Internal moisture causes damage to bushing insulation and can result in explosive failure. This is hazardous to workers and transformer equipment.

Things to check once every 3-5 years

You should be able to run a close physical inspection and cleaning of the bushings. It is required to find out leaks, cracks, and carbon tracking; especially if your transformer is installed in humid environment or near sea. You need to inspect the transformer bushings more often in atmospheres where dust and salts deposits found on the bushings.

In high humidity and wet locations, you may apply a premium quality silicone paste wax to the porcelain as this will lower the risk of flashover. Wax will let water to form beads instead of continuous sheet, which reduces flashover risk.

  • You may use lime removal product for cleaning
  • For stubborn contaminants, you may apply solvents, steel wool, and brushes.
  • High pressure water stream option works for removing salt and other water soluble deposits

All these details are a part of guide shared by distribution transformer manufacturers. If you have any point of doubt, you can ask professionals for assistance. You must follow these guidelines and maintain your transformer bushings like new ones. It’s not tough to perform these checks and tests unless you are first time user of the product.