How Manufacturers Diagnose Their Cast Resin Transformers?

07 May

Cast resin power transformers are exceptionally used by industrial areas that are prone to fire hazards and require environmental protection. For proper functioning of these transformers, cast resin transformer manufacturers perform diagnostic testing on these dry type transformers. The most common reason behind transformer failure is the electric breakdown of the cast resin insulation between parts of the windings. In several cases, partial discharges occur prior the breakdown situation arises. Manufacturers test the windings with induced voltage along with a sensitive PD measurement in the diagnosis process.

Cast resin transformer technologies are now developed and are widely used in applications where safety is a major concern. These transformers are easy to install and have enhanced fire protection. The power and the normal voltage of these transformers were changed in the past few years; these transformers are now built up to 72.5 kV and more than 60 MVA.

While dry type transformers with cast resin technology are maintenance free, regular diagnostic measurements are still needed to prevent transformer breakdown. Manufacturers are short of diagnostic tools for cast resin transformers. They usually perform routine tests during manufacturing process. The process has different stages like-

  • Turns ration measurements
  • Winding DC resistance measurements
  • Voltage ratio and phase displacement measurement
  • Short circuit impedance test
  • Load and no-load test
  • Applied voltage test
  • Induced AC withstand voltage test
  • Partial discharge test

Manufacturers make sure that the frequency of the test voltage should be higher to perform partial discharge measurement. Most f the time, it is the electric breakdown of the cast resin insulation that causes failure of the dry type cast resin transformer. The cast resin insulation is located between turns or parts of the windings. Manufacturers test these windings with induced voltage and partial discharge measurement. This diagnostic method helps minimize the unforeseen breakdowns of the transformer.

Manufacturers do the on-site testing with adequate power supply. They double check the output voltage frequency and ensure that it should be higher than the normal frequency on which transformer operates to prevent excessive magnetizing currents. During operation, transformers may get severe stress due to overloading, overvoltage, pollution, etc. Installation conditions may be more or less serious, such as high connection resistance, closely cables, etc.

Partial discharge measurements are tough to calculate, but manufacturers can get them right after the production. The only challenge they face is to perform these measurements onsite where the transformers are installed and running. They can encounter difficulties like-

  • Lack of accessibility
  • Ambient disturbance

Onsite induced voltage testing and partial discharge measurement when used together becomes the most powerful tool to diagnose cast resin transformer. Manufacturers are utilizing this pair technique to fully check their produced range of transformers. If you want to test dry type transformer, you can consult local cast resin transformers manufacturers for diagnosis run. For further assistance, a lot of transformer repairing and maintenance service providers are available in the market. Contact them for help.

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