Circuit Breaking Interview Questions:

Following are the below Circuit Breaking Interview Questions and Important Questions which is very useful for interviews and exams

1. What is a circuit breaker ? Explain its functions.

2. What are the major duties that a circuit breaker is required to perform ? Explain them clearly.

3. Explain the phenomena of arc formation.

4. Discuss the factors which influence the arc voltage.

5. Discuss different methods of interrupting the arc in circuit breakers. Explain two main theories of current zero interruption.

6. Explain different methods of arc extinction in a circuit breaker.

7. Explain the following terms : (i) Restriking voltage, (ii) Recovery voltage, (iii) RRRV.

8. Discuss recovery rate theory and energy balance theory of arc interruption in a CB.

9. Define the term “active recovery voltage”. Discuss the factors which influence the active recovery voltage of a circuit breaker.

10. Explain the terms recovery voltage, restriking voltage and RRRV. Derive an expression for restriking voltage in terms of system capacitance and inductance.

11. Explain the Slepian’s theory of arc interruption and discuss its limitations.

12. Explain the terms (i) restriking voltage (ii) recovery voltage (iii) RRRV.

13. Derive an expression for the restriking voltage in terms of system voltage, inductance and capacitance across a circuit breaker contact when a 3-phase fault takes place. Assume the neutral of the system to be solidly grounded.

14. Define recovery voltage and active recovery voltage.

15. Discuss the effect of power factor and the amount of asymmetry in the short-circuit wave upon the active recovery voltage.

16. What is a restriking voltage ? Explain why severe voltage oscillations may occur while a circuit breaker is de-energizing a long transmission line which is open circuited at the receiving end.

17. Derive the expression for restriking voltage and RRRV. What measures are taken to reduce it ?

18. Define the terms recovery voltage and rate of rise of restriking voltage. Derive an expression for the latter.

19. Discuss about RRRV. Draw a neat diagram to show the voltages and current during relay and circuit breaker operations. Discuss about recovery voltage, relay operating time, circuit breaking time and circuit making time.

20. What is the significance of RRRV in operation of a circuit breaker ? Also derive the relation for RRRV considering a simple power system.

21. Write short notes with reference to current interruption on (i) Kilometric fault, (ii) Current chopping
phenomena, (iii) Effect of power factor.

22. Explain, ‘successive restrikes’ and current chopping as applied to the interruption of capacitive and low inductive currents.

23. How does resistance switching help in such conditions ?

24. Explain the phenomena of current chopping associated with axial blast circuit breaker. How this dangerous phenomena is rectified by resistance switching ?

25. Explain the phenomenon of current chopping in a circuit breaker.

26. Discuss the problems associated with the interruption of (i) capacitive current (ii) fault current, if fault is very near to the substation.

27. What are the problems associated with short-line interruption ? How is the problem eliminated ?

28. Show how the restriking transients can be damped by connecting a resistance across the contacts of a circuit breaker.

29. Describe resistance switching. What do you understand by pre-insertion resistance and pre-insertion time ?

30. Explain various ratings of a circuit breaker.

31. Explain the following terms referred to a circuit breaker : (a) Symmetrical braking current, (b) Asymmetrical breaking current, (c) RRRV, (d) Making current, (e) Breaking capacity.

32. Explain (i) Making capacity (ii) Breaking capacity (iii) Restriking voltage (iv) Short-line fault (v) Rated operating duty.

33. Discuss in detail the different types of rating of a circuit breaker bringing out clearly their physical significance.

34. What are the usual ratings of a circuit breaker ? Why a circuit breaker has different types of voltage, current and power ratings ?

35. What are the different tests carried out on a circuit breaker ? Differentiate and explain type and routine tests.

36. What is the difference between direct and indirect testing ? Also describe the procedure of indirect testing.

37. How are circuit breakers rated ? Describe the direct and indirect testing of circuit breakers.

38. Describe about the direct and indirect testing procedure for a circuit breaker.

39. Write short notes on the following :

• Switchgcar and circuit breaker.
• ‘High resistance’ and ‘zero point’ interruption of arc in a circuit breaker.
• Duties of circuit breaker.
• Resistance switching.
• Circuit breaker ratings.