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A 60 kV (rms) single core metal sheathed cable is to be graded by means of a metallic intersheath. The safe electric stress of the insutating material is 6 kV/mm (rms). The overal diameter of the intersheath is ________ mm
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- 2.0 mm
- 20 mm
- 0.020 mm
- 200 mm
Correct Option: B
V = 60 kV (rms),
gmax = 6 kV/mm (rms)
| V1 = | = | = 22.1 kV | ||
| e | 2.718 |
| r = | = | = 3.67 mm | ||
| egmax | 2.718 |
Radius of intersheath,
| r1 = | = | = 10 mm | ||
| gmax | 6 |
Diameter of intersheath = 2r1 = 20 mm
