Three Phase Distribution Transformer FAQ 5

41. The primary rated current of the voltage 10/0.4kV transformer is (D) times of the secondary rated current.

A． 25 B． 10 C． 0.4 D． 0.04

42. The iron core of the transformer is made with (C).

A. steel plate B. Copper plate C, silicon steel sheet D. permanent magnet

43. The silica gel in the respirator is in (A) color when dry.

A． light blue b. light red C, deep yellow D. brown

44. The newly put into transformer should run for no-load (C) hours before loading.

A.8 B． 12 C． 24 D． 48

45. The distribution transformers in operation shall conduct a preventive test every (B) year.

A． 1 B． 1-3C． 5 D． 10

46. Before the new transformer is put into operation, (A) no-load full-voltage impact closing test should be carried out.

A.5 B． 3 C． 2 D． 1

47. For distribution transformers that are not frequently overloaded, they must be overhauled at least once every (D) year.

A． 2 B． 3 C． 5 D． 10

48. The height from the bottom of the transformer on the pole to the ground should not be less than (D)m.

A． 1 B． 1.5 C． 2 D． 2.5

49. After the 10kV power distribution system is grounded with low resistance, the protection types that should be installed for 800kVA oil-immersed transformers are: (C)

A．Quick break, over current protection

B. Instant break, overcurrent, gas, temperature protection

C. Instant break, overcurrent, gas, temperature, zero sequence current protection

D．Instant break, overcurrent, gas, temperature, low voltage protection

50. After the gas relay of the transformer operates, the gas collected in the gas relay is characterized by light yellow, strong odor, and flammable, indicating that the transformer is inside (C).

A. Transformer oil releases air B. wooden structure failure C. Paper insulation failure D. Transformer oil failure

51. The maximum current on the low-voltage neutral line of the Yyn0 three-phase four-wire distribution transformer should not exceed (A) of the rated line current.

A.25% B． 50% c． 75% D． 100%

52. The voltage adjustment range of the adjacent gear of the off-load tap changer switch of the commonly used 10kV oil-immersed distribution transformer is (B).

A.2.5% B． 5% c. 7.5% D． 10%

53. When installing an oil-immersed power transformer equipped with a gas relay, there should be (A) from one side of the transformer oil tank to one side of the oil storage tank.

A. Ascending slope B. descending slope C keep level D keep vertical

54. There is no dry-type power transformer (A).

A. Fuel tank B. Iron core C. Temperature measuring device D. solid insulation

55. The following (A) is not a part of the transformer.

A. Junction box B. Fuel tank C. Gas relay D. Explosion-proof tube

56. The cooling fan can be turned off when the oil temperature on the top layer of the oil-immersed air-cooled transformer is (D) °C.

A.25 B.35 C.45 D.55

57. The relationship between the no-load loss of the transformer and the power supply voltage is (D)

A. There is no definite relationship between no-load loss and power supply voltage

B．The no-load loss decreases with the increase of power supply voltage

C. As the power supply voltage increases, the no-load loss increases

D. The no-load loss does not change with the power supply voltage

58. For the transformer of Dyn11 connection group, the phase difference between the secondary line voltage and the primary line voltage is (B).

A, 00 B, 300 C, 600 D, 1100

59. The load rate of the best running state of the transformer is about (B).

A, 50% B, 80% C, 100% D, 110%

60. The tap changer of the distribution transformer is located in the Ⅱ gear, and when the voltage is low for a long time during operation, the measures to be taken are (A).

A. Switch the tap changer to III gear B. Switch the tap changer to I gear

C. Reduce the load D. Ask the power supply department to increase the voltage

61. There is no closed oil-immersed power transformer (B).

A. Oil tank B. Oil conservator C. Thermometer D. Tap changer