1) Mining substations - These are underground and are required for very special purposes.
2) Mobile substations - This is also a special purpose substation required mainly for temporary requirements such as for construction purposes.
3) Cinematograph substations - It is used to meet specific requirements.
📌 Exam-Oriented Key Points
-
Switching substation → No transformer
-
GIS → SF₆ gas, compact
-
Pole-mounted → Rural distribution
-
UHV → Above 400 kV
-
Distribution substation → Consumer supply
1. Substations are classified based on
A. Size only
B. Function, voltage, construction, and supply
C. Cost of equipment
D. Location only
✅ Answer: B
Explanation: Substations are commonly classified by function, voltage level, construction type, and nature of supply.
2. A substation used to increase voltage at the generating station is called
A. Distribution substation
B. Switching substation
C. Generating substation
D. Traction substation
✅ Answer: C
Explanation: Generating substations use step-up transformers to raise voltage for efficient transmission.
3. Which substation does NOT use a transformer?
A. Generating substation
B. Distribution substation
C. Transmission substation
D. Switching substation
✅ Answer: D
Explanation: Switching substations perform switching and control operations only; no voltage transformation occurs.
4. A substation supplying power directly to consumers is called
A. Grid substation
B. Transmission substation
C. Distribution substation
D. Generating substation
✅ Answer: C
Explanation: Distribution substations step down voltage to utilization level (415 V).
5. Voltage level of an Extra High Voltage (EHV) substation is
A. Below 11 kV
B. 11–33 kV
C. 33–66 kV
D. 132–400 kV
✅ Answer: D
Explanation: EHV substations operate at 132 kV and above, up to 400 kV.
6. Which substation is generally installed in densely populated cities?
A. Outdoor substation
B. Pole-mounted substation
C. Underground substation
D. Rural substation
✅ Answer: C
Explanation: Underground substations save space and are used in urban areas.
7. Indoor substations are usually used for voltages up to
A. 400 kV
B. 220 kV
C. 33 kV
D. 11 kV
✅ Answer: D
Explanation: Indoor substations are economical and safe for voltages up to 11 kV.
8. Pole-mounted substations are mainly used for
A. Industrial supply
B. Rural distribution
C. Transmission networks
D. Urban underground supply
✅ Answer: B
Explanation: Pole-mounted substations (11 kV/415 V) are economical for rural areas.
9. A substation that uses SF₆ gas as insulating medium is called
A. AIS
B. GIS
C. Indoor substation
D. Grid substation
✅ Answer: B
Explanation: Gas Insulated Substations (GIS) use SF₆ gas and require less space.
10. Which type of substation requires the least space?
A. Air insulated substation
B. Outdoor substation
C. Gas insulated substation
D. Pole-mounted substation
✅ Answer: C
Explanation: GIS substations are compact and ideal for space-constrained locations.
11. Substations operating above 400 kV are classified as
A. HV
B. EHV
C. UHV
D. MV
✅ Answer: C
Explanation: Ultra High Voltage (UHV) substations operate above 400 kV.
12. Traction substations are mainly used for
A. Residential loads
B. Power generation
C. Railway electrification
D. Rural electrification
✅ Answer: C
Explanation: Traction substations supply power to electric trains and metros.
13. Which substation interconnects transmission lines and maintains system stability?
A. Distribution substation
B. Grid substation
C. Traction substation
D. Pole-mounted substation
✅ Answer: B
Explanation: Grid substations connect transmission networks and regulate voltage.
14. DC substations are mainly used in
A. Household supply
B. AC distribution
C. HVDC and traction systems
D. Rural supply
✅ Answer: C
Explanation: DC substations are used in HVDC transmission and traction applications.
15. Air Insulated Substations (AIS) are preferred when
A. Space is limited
B. Cost must be minimum
C. Indoor installation is required
D. Voltage is below 11 kV
✅ Answer: B
Explanation: AIS substations are cheaper but require more space compared to GIS.
16. A substation converting 33 kV to 11 kV is classified as
A. Generating substation
B. Transmission substation
C. Distribution substation
D. Switching substation
✅ Answer: C
Explanation: Distribution substations reduce voltage to levels suitable for local distribution.
17. Which substation is generally located near the load center?
A. Generating substation
B. Transmission substation
C. Distribution substation
D. Switching substation
✅ Answer: C
Explanation: Distribution substations are installed near consumers to reduce losses.
18. Outdoor substations are commonly used for voltage levels
A. Up to 11 kV
B. Up to 33 kV
C. Above 33 kV
D. Below 415 V
✅ Answer: C
Explanation: Outdoor substations are economical and practical for high voltages.
19. Which classification of substation depends on the insulation medium used?
A. Functional classification
B. Voltage classification
C. Construction classification
D. Insulation-based classification
✅ Answer: D
Explanation: AIS and GIS are classified based on insulation medium.
20. Gas Insulated Substations are preferred in urban areas mainly because
A. Low maintenance
B. High power factor
C. Compact size
D. Simple construction
✅ Answer: C
Explanation: GIS requires very small space, ideal for cities.
21. Which substation uses step-down transformers only?
A. Generating substation
B. Distribution substation
C. Switching substation
D. Grid substation
✅ Answer: B
Explanation: Distribution substations step down voltage for consumer use.
22. A grid substation is mainly used to
A. Supply domestic load
B. Generate power
C. Interconnect transmission lines
D. Convert AC to DC
✅ Answer: C
Explanation: Grid substations connect multiple transmission lines and maintain stability.
23. Which type of substation is MOST economical for rural areas?
A. Underground substation
B. Indoor substation
C. Pole-mounted substation
D. GIS substation
✅ Answer: C
Explanation: Pole-mounted substations are low-cost and ideal for rural distribution.
24. Substations used in HVDC systems are classified as
A. AC substations
B. Distribution substations
C. DC substations
D. Switching substations
✅ Answer: C
Explanation: HVDC systems require DC substations for conversion and control.
25. Which substation classification is based on location and structure?
A. Functional classification
B. Construction classification
C. Voltage classification
D. Service classification
✅ Answer: B
Explanation: Indoor, outdoor, underground, and pole-mounted fall under construction classification.
26. The primary purpose of a traction substation is to
A. Supply residential load
B. Increase transmission voltage
C. Feed power to railways
D. Interconnect grids
✅ Answer: C
Explanation: Traction substations supply power for electric trains and metros.
27. Which substation is mainly used for controlling power flow without voltage change?
A. Generating substation
B. Distribution substation
C. Switching substation
D. Traction substation
✅ Answer: C
Explanation: Switching substations control and protect circuits without transformers.
28. An indoor substation is preferred when
A. Voltage is very high
B. Space is unlimited
C. Voltage is low and safety is important
D. Cost must be minimum
✅ Answer: C
Explanation: Indoor substations provide safety and protection at low voltage levels.
29. Ultra High Voltage (UHV) substations are mainly used for
A. Rural distribution
B. Urban supply
C. Long-distance bulk power transmission
D. Railway supply
✅ Answer: C
Explanation: UHV is used to transmit large power over long distances efficiently.
30. Which of the following is NOT a functional classification of substation?
A. Generating substation
B. Distribution substation
C. GIS substation
D. Switching substation
✅ Answer: C
Explanation: GIS is based on insulation medium, not function.
📌 Quick Revision Points
-
33/11 kV → Distribution substation
-
No transformer → Switching substation
-
Urban + limited space → GIS
-
Rural supply → Pole-mounted
-
>400 kV → UHV
0 टिप्पणियाँ