Previous Year Questions- Generating Power Stations | Power Systems - Electrical Engineering (EE) PDF Download

Q1: The expressions of fuel cost of two thermal generating units as a function of the respective power generation P_G1 and  P_G2 are given as
where aa is a constant. For a given value of a, optimal dispatch requires the total load of 290 MW to be shared as  P_G1 = 175MW and  P_G2 = 115MW. With the load remaining unchanged, the value of a is increased by 10% and optimal dispatch is carried out. The changes in  P_G1 and the total cost of generation, F(=F1 + F2) in Rs/hour will be as follows.      (2023)
(a) $PG1$P_G1 will decrease and F will increase
(b) Both P_G1 and F will increase
(c) P_G1 will increase and F will decrease
(d) Both P_G1 and F will decrease
Ans: (a)
Sol: For optimal dispatch,
IC₁ = IC₂
0.2aP_G1 + 40 = 0.4P_G2 + 30  
Given:
Economic scheduling,
Now, if a increases by 10%,  should be decreases and total cost of generation increases.

Q2: Base load power plants are
P: wind farms.
Q: run-of-river plants.
R: nuclear power plants.
S: diesel power plants.     (SET-1(2015))
(a) P, Q and S only
(b) P, R and S only
(c) P, Q and R only
(d) Q and R only
Ans: (d)

Q3: Out of the following plant categories
(i) Nuclear
(ii) Run-of-river
(iii) Pump Storage
(iv) Diesel
The base load power plant are     (2009)
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (i), (ii) and (iv)
(d) (i), (iii) and (iv)
Ans: (a)
Sol: Pumped storage plants and diesel stations supply power during peak loads.
NOTE: Base load-plant
(i) Low operating cost
(ii) Capability of working continuously long period.

Q4: For harnessing low variable waterheads, the suitable hydraulic turbine with high percentage of reaction and runner adjustable vanes is       (2004)
(a) Kaplan
(b) Francis
(c) Pelton
(d) Impeller
Ans: (a)
Sol: Kaplan is used for run-of-river and poundage stations with heads of upto 70 m (low head). This type has an axial-flow rotor with variable-pitch blades.

Q5: In the thermal power plants, the pressure in the working fluid cycle is developed by       (2004)
(a) condenser
(b) super heater
(c) feed water pump
(d) turbine
Ans: (c)
Sol: NOTE:
Condenser : The function of condenser are
(i) To provide vaccum at outlet of steam turbine.
(ii) To condense the steam ams pass on the condensate to boiler feed.
Super heater is a device used to convert saturated steam or wet steam into dry steam used for power generation process.