BREAKDOWN OF DIELECTRICS

Maximum dielectric strength obtained with pure liquids is about

• (A) 100 kV/mm

• (B) 10 kV/mm

• (C) 1 MV/mm

• (D) 50 kV/mm

Pure liquids are those which are chemically pure and do not contain any impurities in even in the traces of 1 in ________

• (A) 10⁵

• (B) 10¹⁰

• (C) 10⁹

• (D) 10⁴

Example of pure liquid dielectric is

• (A) Silicon oil

• (B) Chlorinated Hydrocarbon

• (C) N-hexane

• (D) Tetrachloroethylene

In purification of liquid dielectric, the following process is used to remove dust

• (A) Distillation

• (B) Filtration

• (C) Degassing

• (D) Chemical treatment

Vacuum drying in liquid purification system remove

• (A) Dust

• (B) Chemical

• (C) Moisture

• (D) Water vapour

Conduction and breakdown in commercial liquids is affected by

• (A) Solid particles

• (B) Vapour or air bubbles

• (C) Electrode material

• (D) All of above

Stressed oil volume theory is applicable when

• (A) Small volume of liquid is involved

• (B) Large volume of liquid is involved

• (C) Large gap distance is involved

• (D) Pure liquids are involved

The intrinsic breakdown strength of solid dielectric is about

• (A) 50 to 100 kV/mm

• (B) 500 to 1000 kV/mm

• (C) 5 to 10 kV/mm

• (D) 1 to 5 kV/mm

The usual mechanism of breakdown in solid dielectric is

• (A) Intrinsic breakdown

• (B) Electromechanical breakdown

• (C) Thermal breakdown

• (D) Chemical breakdown

The thermal breakdown stress is _______ for ac fields then dc fields

• (A) Moderate

• (B) High

• (C) Low

• (D) Equal