Question

In impulse testing of transformers, fault location is usually done by:

• A. Neutral current oscillogram
• B. Chopped wave oscillogram
• C. Observing for noise or smoke
• D. Scanning method

Hint:

In transformer impulse testing, faults are located using the neutral current oscillogram, which shows waveform distortions indicating insulation failure.

Answer 1

The Correct Option is A

Step 1: Impulse Testing of Transformers Impulse testing is conducted to assess the insulation strength of transformers under transient voltage conditions, simulating lightning surges or switching surges. 
Step 2: Fault Detection Methods During impulse testing, faults are identified using oscillographic analysis of current and voltage waveforms. - Neutral Current Oscillogram: 
- Used to detect internal insulation faults in transformers.
- A sudden change in the waveform indicates insulation failure. 
- Chopped Wave Oscillogram: 
- Helps in overvoltage withstand testing but is not primarily used for fault location. 
Step 3: Evaluating options:
- (A) Correct: Neutral current oscillogram effectively detects faults in impulse testing.
- (B) Incorrect: Chopped wave tests insulation performance but not specific fault locations.
- (C) Incorrect: Noise or smoke observation is not a precise fault detection metho(D)
- (D) Incorrect: Scanning is not a standard practice in transformer impulse testing.