Technical Interview: Electrical and Electronics Engineering: Questions

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Electrical and Electronics Engineering

71) Define incremental losses and penalty factor. Explain their significance.

72) What is a heat rate curve? Draw typical heat rate curves for a steam plant and hydro power plant.

73) Explain the co-relation between economic load dispatch of power systems and load frequency control.

74) What do you understand about penalty factors and B-coefficients of economic operation of power systems?

75) Why do we need to maintain power system frequency and voltage remains constant or within the limits?

76) Explain flat frequency control and tie line frequency control methods.

77) Name the type of frequency control system suitable for an interconnection of a small system and a large system.

78) What is the purpose of a national power grid and state its tasks.

79) What are the objectives of automatic generation control? Draw the steady state load frequency characteristics of a speed governor system.

80) What are the functions of reactors in power systems and where do we locate the reactors in power systems?

81) Differentiate between isolators and circuit breaker and explain the sequences of operations used for opening and closing a circuit using isolator.

82) Distinguish between resistance earthing and solid earthing. What are the disadvantages of isolated neutral system?

83) What are the advantages of neutral grounding? What do you understand about Peterson coil earthing and arcing grounds in an overhead line?

84) What do you understand by depreciation of the equipment? Graphically differentiate different methods of determination of depreciation.

85) What information could you get out of integrated load duration curve and load curves?

86) What is meant by tariff? Why two-part tariff is normally used for industries?

87) Differentiate chronological load curve and load curve.

88) Why do we use A. C. S. R conductors for transmission lines? Write the formulae to find the no. of wires in a standard conductor having n layers.

89) What is the significance of maximum prospective short circuit value? How do you calculate the value in a circuit?

90) Draw positive, negative and zero sequence networks for an unloaded generator with solidly grounded neutral.

91) If are the impedances of the load between phases a, b, c to the neutral, then the sequence impedances are.

92) Define and classify stability of a power system. Explain why the transient stability limit is lower than the steady state limit?

93) Define steady state and transient stability limit of a power system. List out the methods to improve steady state and transient stability.

94) State and explain equal area criteria. What are the limitations and advantages of equal area criteria?

95) Draw the diagrams to illustrate the application of equal area criteria to study transient stability for fault and subsequent circuit isolation & study of sudden increase in input of the generator.

96) Explain the effect of change of excitation on steady state stability of a synchronous generator feeding an infinite bus bar?

97) What are the main causes for the study of transient stability problems?

98) Differentiate between transient and dynamic stability. List out the factors that affect power system transient stability.

99) List out the typical values of standard parameters of salient pole machines in p. u with stator base values equal to the corresponding machine rated values.

100) Explain how does auto-reclosing of circuit breakers affects stability of power transmission systems?

101) What is a swing equation? What are the assumptions made in deducing the swing equation?

102) What is meant by synchronizing power coefficient? For what values of synchronizing coefficient, the system remains stable?

103) Difference between a week and a robust power system.

104) Write the swing equations for machines swinging coherently and non-coherently.

105) Explain the importance of reactive power in power in power systems. List out the components of power systems which absorb/generate reactive power.

106) What are the advantages of reactive power compensation? Explain the principle of operation of static VAR compensator.

107) What are the drawbacks in voltage control using generator excitation and series capacities?

108) Compare synchronous capacitors and static capacitors.

109) What is off-nominal transformer ratio? Explain the working principle of booster transformer.

110) What do you understand about loss of excitation and pole slipping of synchronous machines?

111) Explain the effects of frequency and voltage changes on impedance load.

112) Define load flow or power flow. Why do we need to study load flows?

113) What are the practical applications of static load flow studies? Explain how you represent a three winding transformer and phase transformer in load flow studies.

114) What are the different types of buses used in power systems? Explain significance of swing bus.

115) List the different equality and inequality constrains imposed in load flow studies.

116) When do we have to treat a generator bus as a load flow? Explain the reason for it.

117) Explain how the approximation is performed Newton-Raphson method

118) advantages and disadvantages of Newton-Raphson method?

119) Compare G-S and N-R methods.

120) What are the properties of Y bus? Why do we prefer to use Y bus than a Z bus in load flows?

121) What is the significance of base values? What are the advantages of p. u. systems?

122) What are the approximations made in constructing reactance diagram? Explain how you represent different loads in reactance diagram.

123) What are symmetrical components? Draw the positive, negative and zero sequence current vectors for negative sequence protection relay under operation.

124) List out the characteristics of harmonics in power systems. Explain the impact of harmonics on electrical equipment.

125) Differentiate between characteristic and non-characteristics harmonics.

126) Express the unbalanced voltages , in terms of symmetrical components , and vice-versa.

127) Classify synchronous machines. Draw the equivalent circuit diagram of synchronous motor and generator.

128) Classify different types of power systems faults. Why do we need to study fault analysis at all?

129) Explain the methods used to reduce the short circuit currents.

130) How do you represent a power system in load flows and short circuit studies?

131) Rank the different types of faults in the order of severity if the fault is taken place at a given distance.

132) Explain how to determine the synchronous, transient, and sub-transient reactance՚s from oscillogram of the short circuit current.

133) What are symmetrical components? Explain the significance of transient reactance in short circuit studies.

134) Draw the connection diagram of the sequence networks for a double line to ground fault, line-line faults in a power system.

135) What do you understand about short, medium, and long lines? How do you represent them?

136) Draw the schematic diagram of an isochronous governor and the response of generating unit with isochronous governor.

137) What is a stringing chart and sag template? Explain their significance in transmission lines.

138) Explain the method of determining the values and of three-core belted cables.

139) Justify the need for distance protection of transmission lines in an integrated power system.

140) What do you understand by string efficiency? Why it is very low for ordinary insulators strings?

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