61. In a transformer, an insulating material may fail due to
- moisture
- dust
- voids in the winding
- any one or more of the above
62. The function of oil in a transformer is
- to provide insulation and cooling
- to provide protection against lightning
- to provide protection against short circuit
- to provide lubrication
63. The color of fresh dielectric oil used in transformers is
- dark brown
- pale yellow
- pale pink
- white grey
64. The transformer oil should have
- low volatility and high dielectric strength
- good resistance to emulsion with water
- low viscosity to provide good heat transfer
- all of the above
65. Transformer oil must be free from
- moisture
- sludges
- gases
- sulphur
66. The core and windings of a transformer are put in a steel tank in order to
- make it suitable for outdoor operation
- provide protection against mechanical damages and provide additional cooling
- improve its appearance
- all the above
67. In a transformer, conservator is used
- to take up the expansion of oil due to temperature rise
- to act as an oil storage
- for better cooling of transformer
- none of the above
68. Sludge formation in transformer oil due to which one of the following?
- ingress of dust particles and moisture in the oil
- appearance of small fragments of paper, varnish, cotton and other organic materials in the oil
- chemical reaction of transformer oil with the insulating materials
- oxidation of transformer oil
69. In a power transformer, the breather is provided in order to
- filter transformer oil
- prevent ingress of moisture with air
- provide oxygen to the cooling oil
- provide fresh air for increasing cooling effect
70. The chemical used in breather of a transformer should have the quality of
- absorbing moisture
- ionizing air
- cleansing the transformer oil
- none of the above