Three Phase Distribution Transformer FAQ 1

1. For three phase distribution transformer that has been stopped for a long time, it is necessary to measure the insulation resistance and do the oil withstand voltage test before it is put into operation again_____ (C)

A. One month B. Three months C. Half a year D. One year

2. After adjusting the tap changer, measure its contact resistance, the difference between three times should not exceed ______ (A)

A, 2% B, 2.5% C, 3% D, 5%

3. For a three phase distribution transformer newly put into operation, the time required for no-load operation is _______ (C)

A, 8h B, 16h C, 24h D, 48h

4. For transformers in motion, the time limit for preventive tests is ________ (B)

A. Half a year B. One to three years C. Two years D. Five years

5. When three phase distribution transformer is in normal operation, the neutral line current should not exceed the ________ of the corresponding line current (C)

A, 15% B, 20% C, 25% D, 30%

6. The three phase distribution transformer will generate operating overvoltage under the following conditions ________ (C)

A. Closing B. Closing C. Closing and closing D. Misoperation

7. The basis for judging whether a three phase distribution transformer is overloaded is ________ (D)

A. Active power B. Reactive power C. Voltage D. Current

8. The direct grounding resistance value of the neutral wire of the transformer low-voltage winding is ________ (A)

A, 4Ω B, 5Ω C, 10Ω D, 30Ω

9. The maximum capacity of the three phase distribution transformer installed on the pole is ________ (C)

A, 160kVA B, 250kVA C, 315kVA D, 500kVA

10. The transformer current breaks quickly and the overcurrent protection operates, and the circuit breaker should issue a ________ (C) after tripping

A. Instantaneous forecast signal B. Delayed forecast signal C. Accident signal D. No signal