Year 2024

Week # 2 Quiz 4

Q1. A 3-phase transmission line is being supported by three disc insulators. The potentials across top unit (i.e., near to the tower) and middle unit are 8 kV and 12 kV respectively. Calculate the string efficiency.

Q2. When the load impedance is equal to the characteristic impedance of the transmission lines, then the reflection coefficient and standing wave ratio are, respectively _____ .

Q3. A 3-phase transmission line supplies delta connected load of impedance Z. The conductor 'c' of the line develops an open circuit fault as shown in figure. The positive sequence current component in line 'a' will be

Q4. The severity of line-to-ground and 3-phase faults at the terminals of an unloaded star connected synchronous generator is to be same. If the terminal voltage is 1 p.u. and \(X_1=X_2=j.035\) p.u., \(X_{g0}=j0.05\) p.u. for the alternator, then the required inductive reactance for neutral grounding is ________.

Q5. The inductance of transmission line is 1mH/km. If the spacing between conductors is made double the new inductance of line will be approx.

Q6. In case of interconnected power system, if the input to the prime mover of an alternator is kept constant but the excitation is changed, then the

Q7. A string insulator has \(5\) units. The voltage across the bottom most unit is \(30\%\) of total voltage. Its string efficiency is

Q8. Three generators are connected in parallel whose ratings are as follows: \(G_1: 100 MVA, 12 kV, X_{g1} = 0.1 pu\) \(G_2: 200 MVA, 12 kV, X_{g2} = 0.15 pu\) \(G_3: 150 MVA, 15 kV, X_{g3} = 0.15 pu\) Find the equivalent per unit reactance of the system on 200 MVA, 15 kV system base.

Q9. A 2 bus system and corresponding zero sequence network are shown in figure.
The transformers \(T_1\) and \(T_2\) are connected as

Q10. A transmission line is compensated with degree of shunt capacitance \(K_{csh} = 0.2\). If the uncompensated transmission line surge impedance loading is \(SIL =400 MW\), then find the new surge impedance loading \(SIL ^{'}\) after shunt compensation.