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00000EE405 121903

PART C
Answer any two full questions, each carries 10 marks.
Which are the main factors to be taken into account for the selection of cables?

Explain.

Fault current anticipated in a location is 8000A. soil resistivity = 10 Q-m. Earth
resistance is limited to 1Q. Design an earthing system. Fault duration can be
taken 85 3seconds. Plate electrode of 1.2m 1.2mx12.5mm shall be used.

Which are the pre-commissioning tests on power transformers used in an
electrical installation? Explain.

An industrial electrical installation has a demand of 50 kW at a power factor of
0.75 lagging. Determine the rating of the capacitor bank required to improve
the power factor to 0.95 lagging.

An outdoor pole mounted 11kV/433 V substation has to be installed for supply
to a residential area having a load of 63 kVA. With the help of a neat diagram,
make a list of materials required.

Explain the substation earthing system.

PART D
Answer any two full questions, each carries 10 marks.

What are the laws of illumination? Explain with a neat diagram.

A corridor is lighted by 4 lamps spaced 10 m apart and suspended at a height of
5 m above the centre line of the floor. If each lamp gives 200 candle-power in
all directions below the horizontal, find the illumination at the point on the
floor mid-way between the second and third lamps.

Explain with the help of block diagram the working of automatic main failure
system.

Explain with the help of schematic, the necessary protections to be provided for
a 100 kVA standby diesel generator installed in an electrical installation.

What are the design considerations of solar PV system for domestic

applications?

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