Power Systems-I Previous paper

1. (a) What are the main parts of a reactor? Explain the function of each component.[7]

(b) Why is the site near a sea or river or lake and away from thickly populated

area is considered on ideal site for nuclear power plants?[8]

2. A 100 MW power station delivers 100 MW for 2 hours, 50 MW for 6 hours and

is shut down for the rest of each day. It is also shut down for maintenance for 45

days each year. Calculate its annual load factor. [15]

3. In a 3-phase 4-wire distribution system with 240 volts between lines and neutral
there is a balanced motor load of 250 kW at power factor 0.8 lamp loads connected
between respective lines and neutral absorb 25 kW, 75 kW and 100kW.
Calculate:
(a) the current in each line
(b) the current in neutral wire of the feeder. [11+4]
4. What is the importance of interest on capital investment in calculating the cost of
electrical energy? [15]

5. A single phase line (ABC) of length 2 Km having resistance and reactance (go and

return) as 0.06 and 0.1 ohms/km. A is the feeding point, B is the mid point of the

line taking a load of 100 A at 0.9 p.f lead and C is the far end taking a load of 120

A at UPF. The Voltage at the `C' is 230 V. Find the voltage at the sending end

and the phase angle di erence between the voltages of two ends, if:

(a) Power factors of the loads are with reference to far end voltage.

(b) Power factors of the loads are with reference to the voltages at the load points.

[7+8]
6. (a) Draw a general layout of a modern thermal power plant and explain the work-
ing of di erent circuits:
(b) Explain the function of the following in thermal power plant and explain the
principle of operation of each:
i. Economiser
ii. Electrostatic precipitator
iii. Condenser
iv. Superheater
v. Cooling tower. [7+8]
7. (a) Draw and explain key diagram of a typical 11kv/400v indoor substation show-
ing location of all equipment.
(b) What are advantages of single bus bar scheme with sectionalization? [8+7]
8. Show that the economical limit to which the power factor of a load can be raised is
independent of the original value of power factor when the tari consists of a xed
charge per kVA maximum demand plus a
at rate per kWh. [15]