PSA III Year 2024 - 25

Which among these is the major advantage of per unit computations?

• Per unit impedance of transformers is the same referred to either side of it.

• For simulating steady state and transient models in the computer this method is very useful.

• Manufactures usually specify the impedance of an apparatus in per unit system.

• All of these

What is the per unit system (PU)?

• A ratio of actual value in any units to the base or reference value in the same units

• A ratio of the base or reference value in any units to the actual value in the same units

• Ratio of the square of the actual value in any units to the square of base

• reference value in the same unit

What is the simplified diagram called, after omitting all resistances, static loads, capacitance of the transmission lines and magnetizing circuit of the transformer?

• Single line diagram

• Resistance diagram

• Reactance diagram

• None of these

What is the formula to calculate the (kV)B on the HT section?

• (kV)B on HT section (HT voltage rating)/(LT voltage rating)

• (kV)B on LT section (HT voltage rating)/(LT voltage rating)

• (kV)B on HT section (LT voltage rating) / (HT voltage rating)

• (kV)B on LT section (LT voltage rating) / (HT voltage rating)

The value of off diagonal elements is

• which is connected between bus i and bus j with negative sign

• which is connected between bus i and bus j with positive sign

• sum of admittance connected at bus i

• sum of admittance connected at bus j

For n bus power system size of Y bus matrix is

• (n-1)x(n-1)

• (n-2)x(n-2)

• nxn

• (n-1)x(n-2)

Advantage of Gauss-Seidel method is

• applicable for large power system network

• calculation time for each iteration is less

• number of iterations are less

• all of the above

For load flow studies, what are the quantities specified at load bus are ______

• P and V

• P and Q

• V and δ

• δ and Q

Range of accelerating factor is

• 50 to 100

• 1.3 to 1.7

• 1 to 10

• 10.8 to 11.2

Why are load flow studies carried out?

• To study of stability of the system

• For fault calculations

• For planning the power system

• All the above