What is used as insulation for PILC cable?

1 Answer

Answer :

Impregnated paper.  

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Last Answer : Answer: A

Description : The ‘sheath’ is used in cable to (A) provide strength to the cable. (B) provide proper insulation. (C) prevent the moisture from entering the cable. (D) avoid chances of rust on strands.

Last Answer : Ans: A The sheath in underground cable is provided to give mechanical strength.

Description : A cylindrical cable of core radius 1.25cm and impregnated paper insulation of thickness 2.13cm and relative permittivity 3.5. Compute the capacitance of the cable/km (in nF

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Description : A cable of core radius 1.25cm and impregnated paper insulation of thickness 2.13cm and relative permittivity 3.5. Compute the capacitance of the cable/km(in nF) a) 195.7 b) 179.5 c) 157.9 d) 197.5

Last Answer : a) 195.7

Description : Is a cable is to be designed for use on 1000 kV, which insulation would you prefer ? (a) Polyvinyle chloride (b) Vulcanised rubber (c) Impregnated paper (d) Compressed SFe gas (e) none of the above

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Description : The insulation of the cable decreases with (a) the increase in length of the insulation (b) the decrease in the length of the insulation (c) either (a) or (b) (d) none of the above

Last Answer : (a) the increase in length of the insulation

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Description : In the cables, sheaths are used to (a) prevent the moisture from entering the cable (b) provide enough strength (e) provide proper insulation (d) none of the above

Last Answer : (a) prevent the moisture from entering the cable

Description : If a cable of homogeneous insulation has a maximum stress of 10 kV/mm, then the dielectric strength of insulation should be (a) 5 kV/mm (b) 10 kV/mm (a) 15 kV/mm (d) 30 kV/mm

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Description : A certain cable has an insulation of relative permittivity 4. If the insulation is replaced by one of relative permittivity 2, the capacitance of the cable will become (a) one half (6) double (c) four times (d) none of the above

Last Answer : (a) one half

Description : In a cable, the maximum stress under operating conditions is at (a) insulation layer (b) sheath (c) armour (d) conductor surface

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Description : What materials are commonly used as cushions between cable insulation and metallic armor?

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Last Answer : In a 3-phase extra-high voltage cable, a metallic screen around each core insulation is provided to Give mechanical strength

Description : If the insulation resistance of a cable of length 10 km is 1 mega ohm, its insulation resistance for 50 km length will be

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Description : A megger is to measure insulation resistance of a cable. The cable should be connected to   (a) Battery (b) DC supply (c) AC supply (d) No supply  

Last Answer : majorly in DC as well as AC......but ans is Battery

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Description : The removal of paint from electrical equipment, such as generators, should be cautiously undertaken because ____________. A. the mechanical shock of paint removal lessens the dielectric strength ... phase windings frequently become isolated from each other due to dust interference at the terminals

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Description : In preparing to take insulation resistance readings on a main generator, the windings should be grounded for about 15 minutes prior to the test to _____________. A. allow accurate zeroing of the meter ... the windings D. help the windings to cool to the same temperature as the ground test connection

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Description : The insulation of electric generators during short idle periods should be _____________. A. allowed to cool slowly to ambient temperatures B. flashed with direct current to remove any residual ... using strip or space heaters D. relieved of all capacitive charge by grounding the conductors

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Description : Unnecessary and frequent applications of varnish to the generator windings to repair defective insulation will result in ____________. A. heavy coatings of varnish interfering with heat dissipation B. ... of the rectifier assembly D. a built-up of varnish without changing generator operation

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Description : Electrical failures in motors are caused by the breakdown of insulation, which may be caused by _____________. A. penetration of moisture B. accumulation of dirt C. overheating D. all of the above

Last Answer : Answer: D

Description : An open in the armature of a DC motor is suspected, but is not found by visual inspection of the commutator. The next step in troubleshooting this problem is to ________________. A. conduct a ... windings C. conduct an insulation resistance test of the armature D. test the commutator for a ground

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Description : When a megohmmeter is being used on a alternating current machine, the meter pointer will dip toward 'zero' and then gradually rise to the true resistance value if the motor insulation is _____________. A. grounded B. good C. shorted D. dirty

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Description : If air gap readings for an electical generating machine have changed significantly from the last reading, you should check _________. A. the bearings B. insulation readings and machine cleanliness C. the prime mover thrust bearing D. the field coil bolts for the proper torque values

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Description : If deck machinery is expected to be idle for an extended period of time you should____________. A. have electrical safety gloves available in case of electrical shock before running B. perform ... run at regular intervals to inusre correct operation and to renew the internal coating of lubrication

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Description : Air gap readings should be taken periodicly on electrical generation equipment to __________. A. determine the amount of varnish that can be applied to correct insulation problems B. determine the ... field coil bolts and correct lateral adjustment of the field coils D. increase machine efficiency

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Description : On some electrical generating equipment one outboard bearing pedestal is insulated from the bedplate. To check this insulation with the machine assembled you should use a____________. A. ohmmeter with the ... C. megohm meter with the machine running D. voltmeter and ampmeter with the machine running

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