(SEM VII) THEORY EXAMINATION 2017-18 POWER STATION PRACTICE

SECTION A

(Short questions – clear explanation)

1. Explain the role of hydro-electric stations in the power industry.

Hydro-electric power stations play an important role in the power industry because they generate electricity using renewable water energy. They have low operating cost, high efficiency, and no fuel requirement. Hydel stations are especially useful for meeting peak load demand due to their quick start and stop capability. They also help in flood control, irrigation, and water supply, making them multipurpose projects.

2. Explain the mechanism of energy release in nuclear power stations.

In nuclear power stations, energy is released through a process called nuclear fission. When a heavy nucleus such as uranium-235 is bombarded with a slow neutron, it splits into smaller nuclei, releasing a large amount of heat energy and additional neutrons. The heat produced is used to generate steam, which drives a turbine connected to a generator. The released neutrons continue the chain reaction, which is controlled by control rods.

SECTION B

(Medium questions – conceptual explanation)

3. Briefly describe the main parts and working of a steam power station.

A steam power station mainly consists of a boiler, turbine, condenser, cooling tower, and generator. In the boiler, fuel is burned to produce steam at high pressure and temperature. This steam expands in the turbine, causing it to rotate. The turbine shaft is coupled to an alternator, which generates electricity. After leaving the turbine, steam is condensed back into water in the condenser and reused, forming a closed cycle.

4. Explain the general arrangement and operation of a hydroelectric plant.

A hydroelectric plant consists of a dam, reservoir, penstock, turbine, generator, and tailrace. Water stored in the reservoir is released through the penstock under high pressure. This water strikes the turbine blades and causes the turbine to rotate. The turbine drives the generator, producing electricity. After passing through the turbine, water is discharged back to the river through the tailrace.

SECTION C

(Long questions – detailed explanation)

5. Explain the main parts of a nuclear reactor and their functions.

The main parts of a nuclear reactor include fuel rods, moderator, control rods, coolant, and reflector. Fuel rods contain nuclear fuel where fission occurs. The moderator slows down fast neutrons to sustain the chain reaction. Control rods absorb excess neutrons and control the rate of reaction. The coolant removes heat generated in the reactor core and transfers it to the heat exchanger. The reflector reduces neutron leakage and improves efficiency.

6. Describe the main parts and working of a diesel electric power station.

A diesel electric power station consists of a diesel engine, alternator, fuel system, cooling system, lubrication system, and exhaust system. The diesel engine acts as the prime mover. When fuel is injected into the engine cylinder, it burns and produces power, which rotates the crankshaft. This mechanical energy drives the alternator, producing electrical energy. Diesel power stations are commonly used for small-scale generation and emergency backup due to their quick start and reliability.