Unsymmetrical Fault Analysis Interview Questions:

Following are the below Unsymmetrical Fault Analysis Interview Questions and Important Questions which is very useful for interviews and exams

1. Obtain positive, negative and zero sequence networks of an unloaded generator having its neutral grounded through impedances Z_n.

2. A 3-phase synchronous generator with its neutral solidly grounded and operating at no load develops an L-G fault in one of the phases having fault impedance Z_f. Derive expressions for the fault currents and the line-to-ground voltages at the location of the fault at all the phases.

3. Derive an expression for fault current for single line-to­-ground fault by symmetrical component method.

4. Develop the connection diagram of sequence networks for a single line-to-ground (L-G) fault. Also find the expression for fault current in terms of sequence currents in the fault conditions.

5. Derive the sequence network of an unloaded generator for a single line-to-ground fault through fault impedance Z_f.

6. Derive the necessary equation to determine the fault current for L-L fault. Draw a diagram showing the interconnection of sequence networks.

7. What is relationship between V_a1 and V_a2 for solid short circuit between lines b and c ? Does this relationship remain valid if fault is through impedance Z_f. If yes, justify. If not, determine new relationship.

8. Derive the expression for the symmetrical components of fault current of a power system for L-L fault through impedance. How symmetrical networks are connected to have equivalent circuit ?

9. Show that the three symmetrical component sequence-networks are connected in : (i) series for a single line-to-ground fault. (ii) parallel for a bold double line-to-ground fault.

10. A double line-to-ground fault occurs on phase b and c of an unloaded generator. Derive a sequence network representation of this condition and determine the fault current.

11. A double line fault occurs between the two phases of a transmission line with an impedance Z_f between them. Show how the sequence-networks may be connected at the fault point to represent this type of fault. Derive the formula for determining the fault current.

12. Draw connection of sequence networks for L-L-G fault at the terminals of an unloaded generator. Show that this network is identical to that for L-L fault in absence of neutral grounded.

13. Derive the necessary equation to determine the fault current for a double line-to-ground fault.

14. Derive the necessary equation to determine the fault current for a L-L-G fault. Draw a diagram showing the interconnection of sequence networks.

15. Why is 3-Φ symmetrical fault more severe than a 3-Φ unsymmetrical fault ?

16. Give reasons : For a fault at alternator terminals, a single line-to-ground fault is more severe than a 3-Φ fault.

17. Discuss the assumptions made for short-circuit analysis of a power system. Deduce the expression for system impedance matrix in bus frame of reference (Z_BUS) using singular transformation.

18. Discuss the different kinds of faults occurring under unloaded conditions of synchronous generator. Explain the interpretation of the Z_bus matrix. Discuss step-by-step Z_bus formulations.

19. Describe in detail with flow chart diagram, the computational method for short circuit calculations.

20. Write short notes on :

• Analysis of single line-to-ground fault.
• Analysis of double line-to-ground fault.
• Formation of Z_bus using singular transformation.
• Computer method for SC calculations.