Question

Impulse testing of transformers is done to determine the ability of
1. bushings to withstand vibrations
2. insulation to withstand transient voltages
3. windings to withstand voltage fluctuations
4. all of the above

Answer 1

Correct Answer - Option 2 : insulation to withstand transient voltages

Impulse testing:

• Lighting is a common phenomenon in transmission lines because of their tall height. This lightning stroke on the line conductor causes impulse voltage.
• The transformer experiences lightning impulse voltages due to which insulation becomes the most important factor.
• Any weakness in the insulation may cause the failure of the transformer.
• To ensure the effectiveness of the insulation system of a transformer, the dielectric test is used.
• The dielectric test alone cannot determine the dielectric strength of the insulator (for all the frequencies)
• Hence, an impulse test of the transformer performed on it.
• Therefore, Impulse testing of transformers is done to determine the ability of ​insulation to withstand transient voltages.

 

There are two types of impulse test

1. Lightning impulse test
2. Switching impulse test