27 real Power Systems questions from the Electrical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Per-unit system?
Junior
A.the most common fault type, roughly 70–80% of line faults, analysed by connecting the three sequence networks in series
B.expressing quantities as fractions of chosen base values so transformer turns ratios vanish and impedances across voltage levels become comparable
C.receiving-end voltage exceeds sending-end voltage on a lightly loaded or open long line because of the line charging capacitance
D.graphical transient stability test: the machine stays in synchronism if the available decelerating area can match the accelerating area
2. Which term means: "expressing quantities as fractions of chosen base values so transformer turns ratios vanish and impedances across voltage levels become comparable"?
A.Per-unit system — iterative method using the Jacobian of power mismatches that converges quadratically in a few iterations regardless of system size
B.Per-unit system — ionisation of the air around a conductor when its surface gradient exceeds about 30 kV/cm peak, causing loss, audible noise and ozone
C.Per-unit system — M d²δ/dt² equals Pm minus Pe, relating rotor angle acceleration to the mismatch between mechanical input and electrical output
D.Per-unit system — expressing quantities as fractions of chosen base values so transformer turns ratios vanish and impedances across voltage levels become comparable
5. Which term means: "receiving-end voltage exceeds sending-end voltage on a lightly loaded or open long line because of the line charging capacitance"?
A.Ferranti effect — resolution of an unbalanced three-phase set into positive, negative and zero sequence sets so unsymmetrical faults can be analysed
B.Ferranti effect — iterative method using the Jacobian of power mismatches that converges quadratically in a few iterations regardless of system size
C.Ferranti effect — receiving-end voltage exceeds sending-end voltage on a lightly loaded or open long line because of the line charging capacitance
D.Ferranti effect — expressing quantities as fractions of chosen base values so transformer turns ratios vanish and impedances across voltage levels become comparable
8. Which term means: "ionisation of the air around a conductor when its surface gradient exceeds about 30 kV/cm peak, causing loss, audible noise and ozone"?
A.Corona — graphical transient stability test: the machine stays in synchronism if the available decelerating area can match the accelerating area
B.Corona — receiving-end voltage exceeds sending-end voltage on a lightly loaded or open long line because of the line charging capacitance
C.Corona — power delivered when a lossless line is terminated in its characteristic impedance, giving a flat voltage profile and zero net reactive power
D.Corona — ionisation of the air around a conductor when its surface gradient exceeds about 30 kV/cm peak, causing loss, audible noise and ozone
11. Which term means: "resolution of an unbalanced three-phase set into positive, negative and zero sequence sets so unsymmetrical faults can be analysed"?
A.Symmetrical components — power delivered when a lossless line is terminated in its characteristic impedance, giving a flat voltage profile and zero net reactive power
B.Symmetrical components — the most common fault type, roughly 70–80% of line faults, analysed by connecting the three sequence networks in series
C.Symmetrical components — receiving-end voltage exceeds sending-end voltage on a lightly loaded or open long line because of the line charging capacitance
D.Symmetrical components — resolution of an unbalanced three-phase set into positive, negative and zero sequence sets so unsymmetrical faults can be analysed
A.Single line-to-ground fault — resolution of an unbalanced three-phase set into positive, negative and zero sequence sets so unsymmetrical faults can be analysed
B.Single line-to-ground fault — graphical transient stability test: the machine stays in synchronism if the available decelerating area can match the accelerating area
C.Single line-to-ground fault — power delivered when a lossless line is terminated in its characteristic impedance, giving a flat voltage profile and zero net reactive power
D.Single line-to-ground fault — the most common fault type, roughly 70–80% of line faults, analysed by connecting the three sequence networks in series
17. Which term means: "power delivered when a lossless line is terminated in its characteristic impedance, giving a flat voltage profile and zero net reactive power"?
A.Surge impedance loading — graphical transient stability test: the machine stays in synchronism if the available decelerating area can match the accelerating area
B.Surge impedance loading — resolution of an unbalanced three-phase set into positive, negative and zero sequence sets so unsymmetrical faults can be analysed
C.Surge impedance loading — ionisation of the air around a conductor when its surface gradient exceeds about 30 kV/cm peak, causing loss, audible noise and ozone
D.Surge impedance loading — power delivered when a lossless line is terminated in its characteristic impedance, giving a flat voltage profile and zero net reactive power
20. Which term means: "graphical transient stability test: the machine stays in synchronism if the available decelerating area can match the accelerating area"?
A.Equal area criterion — the most common fault type, roughly 70–80% of line faults, analysed by connecting the three sequence networks in series
B.Equal area criterion — expressing quantities as fractions of chosen base values so transformer turns ratios vanish and impedances across voltage levels become comparable
C.Equal area criterion — graphical transient stability test: the machine stays in synchronism if the available decelerating area can match the accelerating area
D.Equal area criterion — iterative method using the Jacobian of power mismatches that converges quadratically in a few iterations regardless of system size
23. Which term means: "iterative method using the Jacobian of power mismatches that converges quadratically in a few iterations regardless of system size"?
A.Newton-Raphson load flow — receiving-end voltage exceeds sending-end voltage on a lightly loaded or open long line because of the line charging capacitance
B.Newton-Raphson load flow — M d²δ/dt² equals Pm minus Pe, relating rotor angle acceleration to the mismatch between mechanical input and electrical output
C.Newton-Raphson load flow — iterative method using the Jacobian of power mismatches that converges quadratically in a few iterations regardless of system size
D.Newton-Raphson load flow — resolution of an unbalanced three-phase set into positive, negative and zero sequence sets so unsymmetrical faults can be analysed
26. Which term means: "M d²δ/dt² equals Pm minus Pe, relating rotor angle acceleration to the mismatch between mechanical input and electrical output"?
A.Swing equation — power delivered when a lossless line is terminated in its characteristic impedance, giving a flat voltage profile and zero net reactive power
B.Swing equation — M d²δ/dt² equals Pm minus Pe, relating rotor angle acceleration to the mismatch between mechanical input and electrical output
C.Swing equation — graphical transient stability test: the machine stays in synchronism if the available decelerating area can match the accelerating area
D.Swing equation — the most common fault type, roughly 70–80% of line faults, analysed by connecting the three sequence networks in series
Answers, AI explanations, and a free readiness check
Sign up free to check your answers with explanations, ask the AI tutor anything on any question, and take the free 2-minute readiness check for a scored result. The full AI mock interview, scored like a real panel, unlocks with Pro.