Transformer Testing

• Testing is the most important activity when any equipment is designed.
• While testing, basic testing requirements and testing codes are set out in the national and international standards.

Transformer Testing

Preliminay Test

Carried out on transformer before it is put into the tank.

Final Test

Carried out on completely assembles transformer.

Preliminary Tests

Core Insulation

When the core is assembled in a transformer, 2kv test is done to ensure that the insulation between clamp plates, core bolts and core is adequate.

Core Loss Test

This test is conducted on the core assembly to ensure its soundness. Some of the coils are wound over the core and it us energized at normal flux density. As a result, coreloss and magnetizing current (I_µ) are noted and compared with design value.

Ratio Test

Ratio test is conducted to check the correctness of voltage ratio between differenet windings on each tapping. The tolerance allowed for ratio on each tapping is ± 0.5%

Final Tests

Routine Test

Measurement of voltage ratio. Measurement of winding resistance. Measurement of impedance voltage, short circuit impedance and load loss. Measurement of no load loss and current. Measurement of insulation resistance. Tests on-load tapchangers Dielectric Test

Type Test

Measurement of voltage ratio. Measurement of winding resistance. Measurement of impedance voltage, short circuit impedance and load loss. Measurement of no load loss and current. Measurement of insulation resistance. Tests on-load tapchangers Dielectric Test Temperature rise test. Dielectric type tests.

Special Test

Short-circuit test. Dielectric special tests. Measurement of acoustic noice level. Measurement of zero-sequence impedance of 3Φ transformers Measurement of harmonics of the no load current. Measurement of power taken by the fans and oil pumps. Measurement of transferred surge voltage on low voltage windings. Measurement of capacitances between windings to earth and between windings. Measurement of Insulation resistance to earth of the windings. Measurement of dissipation factor of the insulation system capacitance.