Testing on 10MVA Power Transformer

by

Type Tests for the transformer

  1. Checking of Acoustic Noise Level
  2. Temperature Rise Test
  3. Lightning Impulse Withstand Test
  4. Pressure and Vacuum Test on finished empty tanks during stage inspection.

Routine Tests on the Transformer

  1. Resistance of each winding at all taps (wherever applicable).
  2. Turns ratio for all sets of windings on each tap.
  3. Polarity and phase vector relationship verification.
  4. Measurement of No Load Loss and No Load Current at 90%, 100%, and 110% rated voltage.
  5. Impedance voltage at normal, maximum, and minimum tap for each pair of windings.
  6. Measurement of insulation resistance between windings and between windings and earth. The IR value is to be measured before and after the impulse test.
  7. Regulation at rated load and at unity, 0.8 lagging power factors.
  8. Efficiencies at unity power factor and 0.8 power factor at 50%, 75%, and 100% loading.
  9. Measurement of Load Losses.
  10. Separate source voltage withstand test.
  11. Induced overvoltage withstand test.
  12. Magnetic Balance test.
  13. Oil leakage test on tanks and all oil-filled compartments. The transformer shall be tested for 12 hours (minimum) filled with oil to ensure no oil leaks occur.
  14. Test on pressure relief device.
  15. Measurement of Tan Delta and Capacitance of Windings.
  16. Zero Sequence Impedance measurement.
  17. Test on tank-mounted marshalling box.
  18. BDV (Breakdown Voltage) measurement of transformer oil.
  19. Visual and dimensional checking of the transformer.

Stage Inspection Tests

On Core:

  1. Flux density checking of assembled core.
  2. Measurement of step width, lamination thickness, window height, leg center dimension, and core diameter of the assembled core.
  3. Physical verification of core concerning uniformity of lamination thickness, bend, camber, and waviness.
  4. Carlite test, watt loss, and aging test on a sample of the prime core (samples are selected during stage inspection and sent to an NABL-accredited laboratory for testing).
  5. Loss measurement of the prime core (watt/Kg).
  6. 2KV test between the core and yoke clamps.

On Coil

  1. Physical verification of HV and LV wound coils.
  2. Measurement of resistance of each finished coil (HV & LV).
  3. Measurement and current density calculation of each winding.
  4. Copper purity test (after cutting from the finished coil offered for inspection).

On Tank

  1. Physical inspection and dimension checking of the main tank.
  2. Vacuum withstand test on the main tank.
  3. Pressure withstand test on the main tank.

Acceptance Tests

  1. All the routine tests listed above are to be performed 100% of ordered transformers.
  2. All the type tests listed above are to be performed on one randomly selected transformer among the ordered transformers.