78. A transmission line of 80 km length is operating at 400 Hz, it can be classified as
A. Short length line
B. Medium length line
C. Long length line
D. all of the above

---

79. The main consideration for higher and higher operating voltage of transmission is to
A. increase efficiency of transmission
B. reduce power losses
C. increase power transfer capability
D. and

---

80. When there is a change in load in a power station having a number of generator units operating in parallel, the system frequency is controlled by
A. adjusting the steam input to the units
B. adjusting the field-excitation of the generators
C. chaning the load divisions between the units
D. injecting reactive power at the station bus bar

---

81. The flow-duration curve at a given head of a hydro-electric plant is used to determine the
A. total power available at the site
B. total units of energy available
C. load-factor at the plant
D. diversity-factor for the plant.

---

82. In the optimum generator scheduling of different power plants, the minimum fuel cost is obtained when
A. only the incremental fuel cost of each plant is the same
B. the penalty factor of each plant is the same
C. the ratio of the incremental fuel cost to the penalty factor of each plant is the same
D. the incremental fuel cost of each plant multiplied by its penalty factor is the same.

---

83. A hydel power plant of run-off-river should be provided with a pondage so that the
A. firm-capacity of the plant is increased
B. operating head is controlled
C. pressure inside the turbine casing remains constant
D. kinetic energy of the running water is fully utilised

---

84. Which of the following are the advantages of interconnected operation of power system? 1..Less reserve capacity requirement 2. More reliability 3. High power factor 4. Reduction in short-circuit level Select the correct answer using the codes given below : Codes :
A. 1 and 2
B. 2 and 3
C. 3 and 4
D. 1 and 4

---