33 real Substation Design questions from the Electrical Design 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 Single line diagram?
Junior
A.one-line representation of the three-phase system showing transformers, breakers, isolators, CTs, PTs and protection, the master drawing of any substation
B.gas-insulated switchgear needs about 10–20% of the air-insulated footprint and suits polluted or urban sites, at higher capital cost and SF6 handling duties
C.the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
D.an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks
2. Which term means: "one-line representation of the three-phase system showing transformers, breakers, isolators, CTs, PTs and protection, the master drawing of any substation"?
A.Single line diagram — the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
B.Single line diagram — minimum air distance from live parts to earthed structures, about 1300 mm at 132 kV, 2100 mm at 220 kV and 3500 mm at 400 kV
C.Single line diagram — an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks
D.Single line diagram — one-line representation of the three-phase system showing transformers, breakers, isolators, CTs, PTs and protection, the master drawing of any substation
A.the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
B.grid conductor sized on fault current and duration, then mesh and step voltages are checked against tolerable limits from body weight and gravel resistivity
C.minimum air distance from live parts to earthed structures, about 1300 mm at 132 kV, 2100 mm at 220 kV and 3500 mm at 400 kV
D.transfer bus with a bus coupler lets a feeder breaker be taken out for maintenance while the feeder stays supplied, common at 132 kV
5. Which term means: "transfer bus with a bus coupler lets a feeder breaker be taken out for maintenance while the feeder stays supplied, common at 132 kV"?
A.Main and transfer bus — the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
B.Main and transfer bus — transfer bus with a bus coupler lets a feeder breaker be taken out for maintenance while the feeder stays supplied, common at 132 kV
C.Main and transfer bus — each feeder can be transferred between two main buses by isolators, allowing bus maintenance without feeder outage but breaker maintenance needs one
D.Main and transfer bus — three breakers per two circuits between two main buses, giving no feeder outage for any breaker fault, standard at 400 kV and above
8. Which term means: "the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout"?
11. Which term means: "an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks"?
A.Isolator vs breaker — three breakers per two circuits between two main buses, giving no feeder outage for any breaker fault, standard at 400 kV and above
B.Isolator vs breaker — selecting equipment withstand levels (BIL/SIL) against surge arrester protective levels with a margin of at least 20% per IEC 60071
C.Isolator vs breaker — the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
D.Isolator vs breaker — an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks
A.transfer bus with a bus coupler lets a feeder breaker be taken out for maintenance while the feeder stays supplied, common at 132 kV
B.each feeder can be transferred between two main buses by isolators, allowing bus maintenance without feeder outage but breaker maintenance needs one
C.three breakers per two circuits between two main buses, giving no feeder outage for any breaker fault, standard at 400 kV and above
D.grid conductor sized on fault current and duration, then mesh and step voltages are checked against tolerable limits from body weight and gravel resistivity
14. Which term means: "three breakers per two circuits between two main buses, giving no feeder outage for any breaker fault, standard at 400 kV and above"?
A.One-and-a-half breaker scheme — grid conductor sized on fault current and duration, then mesh and step voltages are checked against tolerable limits from body weight and gravel resistivity
B.One-and-a-half breaker scheme — gas-insulated switchgear needs about 10–20% of the air-insulated footprint and suits polluted or urban sites, at higher capital cost and SF6 handling duties
C.One-and-a-half breaker scheme — three breakers per two circuits between two main buses, giving no feeder outage for any breaker fault, standard at 400 kV and above
D.One-and-a-half breaker scheme — the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
A.one-line representation of the three-phase system showing transformers, breakers, isolators, CTs, PTs and protection, the master drawing of any substation
B.overhead earth wires or masts placed so the rolling-sphere or 30–45° protective-angle zone covers every live conductor per IS/IEC 62305
C.gas-insulated switchgear needs about 10–20% of the air-insulated footprint and suits polluted or urban sites, at higher capital cost and SF6 handling duties
D.each feeder can be transferred between two main buses by isolators, allowing bus maintenance without feeder outage but breaker maintenance needs one
17. Which term means: "each feeder can be transferred between two main buses by isolators, allowing bus maintenance without feeder outage but breaker maintenance needs one"?
A.Double bus single breaker — each feeder can be transferred between two main buses by isolators, allowing bus maintenance without feeder outage but breaker maintenance needs one
B.Double bus single breaker — the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
C.Double bus single breaker — minimum air distance from live parts to earthed structures, about 1300 mm at 132 kV, 2100 mm at 220 kV and 3500 mm at 400 kV
D.Double bus single breaker — transfer bus with a bus coupler lets a feeder breaker be taken out for maintenance while the feeder stays supplied, common at 132 kV
A.the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
B.minimum air distance from live parts to earthed structures, about 1300 mm at 132 kV, 2100 mm at 220 kV and 3500 mm at 400 kV
C.an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks
D.gas-insulated switchgear needs about 10–20% of the air-insulated footprint and suits polluted or urban sites, at higher capital cost and SF6 handling duties
A.Phase-to-earth clearance — an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks
B.Phase-to-earth clearance — selecting equipment withstand levels (BIL/SIL) against surge arrester protective levels with a margin of at least 20% per IEC 60071
C.Phase-to-earth clearance — grid conductor sized on fault current and duration, then mesh and step voltages are checked against tolerable limits from body weight and gravel resistivity
D.Phase-to-earth clearance — minimum air distance from live parts to earthed structures, about 1300 mm at 132 kV, 2100 mm at 220 kV and 3500 mm at 400 kV
A.grid conductor sized on fault current and duration, then mesh and step voltages are checked against tolerable limits from body weight and gravel resistivity
B.transfer bus with a bus coupler lets a feeder breaker be taken out for maintenance while the feeder stays supplied, common at 132 kV
C.one-line representation of the three-phase system showing transformers, breakers, isolators, CTs, PTs and protection, the master drawing of any substation
D.selecting equipment withstand levels (BIL/SIL) against surge arrester protective levels with a margin of at least 20% per IEC 60071
23. Which term means: "grid conductor sized on fault current and duration, then mesh and step voltages are checked against tolerable limits from body weight and gravel resistivity"?
A.IEEE 80 earthing mat design — grid conductor sized on fault current and duration, then mesh and step voltages are checked against tolerable limits from body weight and gravel resistivity
B.IEEE 80 earthing mat design — selecting equipment withstand levels (BIL/SIL) against surge arrester protective levels with a margin of at least 20% per IEC 60071
C.IEEE 80 earthing mat design — an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks
D.IEEE 80 earthing mat design — one-line representation of the three-phase system showing transformers, breakers, isolators, CTs, PTs and protection, the master drawing of any substation
A.gas-insulated switchgear needs about 10–20% of the air-insulated footprint and suits polluted or urban sites, at higher capital cost and SF6 handling duties
B.each feeder can be transferred between two main buses by isolators, allowing bus maintenance without feeder outage but breaker maintenance needs one
C.the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
D.overhead earth wires or masts placed so the rolling-sphere or 30–45° protective-angle zone covers every live conductor per IS/IEC 62305
26. Which term means: "gas-insulated switchgear needs about 10–20% of the air-insulated footprint and suits polluted or urban sites, at higher capital cost and SF6 handling duties"?
A.GIS vs AIS — the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
B.GIS vs AIS — minimum air distance from live parts to earthed structures, about 1300 mm at 132 kV, 2100 mm at 220 kV and 3500 mm at 400 kV
C.GIS vs AIS — selecting equipment withstand levels (BIL/SIL) against surge arrester protective levels with a margin of at least 20% per IEC 60071
D.GIS vs AIS — gas-insulated switchgear needs about 10–20% of the air-insulated footprint and suits polluted or urban sites, at higher capital cost and SF6 handling duties
A.selecting equipment withstand levels (BIL/SIL) against surge arrester protective levels with a margin of at least 20% per IEC 60071
B.gas-insulated switchgear needs about 10–20% of the air-insulated footprint and suits polluted or urban sites, at higher capital cost and SF6 handling duties
C.an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks
D.one-line representation of the three-phase system showing transformers, breakers, isolators, CTs, PTs and protection, the master drawing of any substation
29. Which term means: "selecting equipment withstand levels (BIL/SIL) against surge arrester protective levels with a margin of at least 20% per IEC 60071"?
A.Insulation coordination — three breakers per two circuits between two main buses, giving no feeder outage for any breaker fault, standard at 400 kV and above
B.Insulation coordination — selecting equipment withstand levels (BIL/SIL) against surge arrester protective levels with a margin of at least 20% per IEC 60071
C.Insulation coordination — an isolator is an off-load device giving visible isolation and must be operated only after the breaker has opened, enforced by interlocks
D.Insulation coordination — the set of breaker, isolators, CTs, PT and earth switch controlling one circuit, whose width and depth fix the switchyard layout
Showing 30 of 33 Substation Design questions — the full set, with answers, explanations and an AI tutor on every question, is inside.
Free to start
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.