100 MCQs on Power Systems JKSSB Junior Engineer (Electrical)|exam, covering generation, transmission, distribution, protection, and related concepts.

Below are **100 MCQs on Power Systems** for **JKSSB Junior Engineer (Electrical)** exam, covering generation, transmission, distribution, protection, and related concepts. Each question includes the answer and a concise explanation.

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### **Power Systems MCQs (JKSSB JE Electrical)**
**1. Which power plant has the highest operating cost?**
A. Hydroelectric
B. Nuclear
C. Thermal (Coal)
D. Diesel
**Answer: D**
*Explanation:* Diesel plants have high fuel costs, making them the most expensive for generation.

**2. The primary source of energy in a hydroelectric plant is:**
A. Uranium
B. Wind
C. Water
D. Biomass
**Answer: C**
*Explanation:* Potential/kinetic energy of water drives hydro turbines.

**3. In thermal power plants, the function of a condenser is to:**
A. Condense steam into water
B. Cool generator windings
C. Filter flue gases
D. Remove ash
**Answer: A**
*Explanation:* Condensers convert exhaust steam back to water for reuse.

**4. The grid frequency in India is maintained at:**
A. 50 Hz
B. 60 Hz
C. 25 Hz
D. 100 Hz
**Answer: A**
*Explanation:* India uses 50 Hz; the USA uses 60 Hz.

**5. Skin effect occurs in:**
A. DC transmission
B. AC transmission
C. Both AC and DC
D. Underground cables
**Answer: B**
*Explanation:* Skin effect (current crowding near conductor surface) is exclusive to AC.

**6. Surge impedance loading (SIL) is associated with:**
A. Transformers
B. Transmission lines
C. Generators
D. Capacitors
**Answer: B**
*Explanation:* SIL = \( \frac{V^2}{Z_c} \), where \( Z_c \) is the line’s surge impedance.

**7. A “disc insulator” is used in transmission lines for:**
A. Voltage transformation
B. Mechanical support and insulation
C. Power factor correction
D. Fault detection
**Answer: B**
*Explanation:* Disc insulators isolate conductors from towers electrically and mechanically.

**8. The purpose of a “gravel” in a substation yard is to:**
A. Improve aesthetics
B. Suppress fire from oil spills
C. Reduce soil erosion
D. Prevent weed growth
**Answer: B**
*Explanation:* Gravel absorbs oil spills and prevents fire propagation.

**9. For a 400 kV transmission line, the number of insulator discs typically used is:**
A. 3–4
B. 8–10
C. 15–18
D. 22–25
**Answer: D**
*Explanation:* 400 kV lines require 22–25 discs (standard: 1 disc per 11–15 kV).

**10. Buchholz relay protects:**
A. Transformers
B. Generators
C. Motors
D. Transmission lines
**Answer: A**
*Explanation:* It detects gas/oil flow from internal faults in oil-immersed transformers.

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### **Transmission & Distribution**
**11. ACSR conductor stands for:**
A. Aluminum Core Steel Reinforced
B. Aluminum Conductor Steel Reinforced
C. Alloy-Coated Steel Rod
D. Aluminum Cable Steel Resistant
**Answer: B**
*Explanation:* ACSR has aluminum strands over a steel core for strength.

**12. The voltage level for rural distribution in India is typically:**
A. 11 kV
B. 33 kV
C. 66 kV
D. 132 kV
**Answer: A**
*Explanation:* 11 kV is standard for rural feeders; 415/240 V for end-users.

**13. Proximity effect is most significant in:**
A. Overhead lines
B. Underground cables
C. Busbars
D. Transformers
**Answer: C**
*Explanation:* Proximity effect (current redistribution due to nearby conductors) is critical in busbars.

**14. The sag of a transmission line increases when:**
A. Temperature rises
B. Temperature falls
C. Wind speed increases
D. Ice loading occurs
**Answer: A**
*Explanation:* Sag ∝ temperature (due to thermal expansion).

**15. A “feeder” in a distribution system:**
A. Supplies power to distributors
B. Connects consumers directly
C. Steps down voltage
D. Measures energy
**Answer: A**
*Explanation:* Feeders carry power from substations to distributors.

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### **Switchgear & Protection**
**16. Arc quenching in circuit breakers is achieved using:**
A. SF₆ gas
B. Transformer oil
C. Vacuum
D. All of these
**Answer: D**
*Explanation:* SF₆, oil, vacuum, and air blast are common quenching media.

**17. An IDMT relay is used for:**
A. Overcurrent protection
B. Differential protection
C. Distance protection
D. Underfrequency protection
**Answer: A**
*Explanation:* Inverse Definite Minimum Time (IDMT) relays protect against overcurrent.

**18. The breaking capacity of a circuit breaker is expressed in:**
A. Volts
B. Amperes
C. MVA
D. Hz
**Answer: C**
*Explanation:* Breaking capacity = \( \sqrt{3} \times V_{\text{rated}} \times I_{\text{fault}} \) (MVA).

**19. For transformer protection, the preferred relay is:**
A. Overcurrent relay
B. Buchholz relay
C. Impedance relay
D. Directional relay
**Answer: B**
*Explanation:* Buchholz detects incipient faults via gas accumulation.

**20. A “lightning arrester” is installed:**
A. Near transformers
B. At line terminations
C. On towers
D. All of these
**Answer: D**
*Explanation:* Arresters protect equipment from voltage surges at entry/exit points.

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### **Load Flow & Stability**
**21. The main objective of a “load flow study” is to determine:**
A. Fault currents
B. Voltage profiles and power flows
C. Stability limits
D. Relay settings
**Answer: B**
*Explanation:* Load flow calculates voltages, real/reactive power in a steady-state system.

**22. A slack bus in load flow analysis is responsible for:**
A. Voltage control
B. Supplying losses
C. Frequency regulation
D. Both (A) and (B)
**Answer: D**
*Explanation:* Slack bus balances power losses and often controls voltage.

**23. Transient stability is affected by:**
A. Fault duration
B. Generator inertia
C. Excitation systems
D. All of these
**Answer: D**
*Explanation:* All factors influence a generator’s ability to maintain synchronism after faults.

**24. The critical clearing time is the maximum time:**
A. To isolate a fault without loss of stability
B. For relay operation
C. To restore voltage
D. For circuit breaker opening
**Answer: A**
*Explanation:* Critical clearing time ensures system remains stable post-fault.

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### **Cables & Insulation**
**25. Belted cables are used up to:**
A. 11 kV
B. 33 kV
C. 66 kV
D. 132 kV
**Answer: A**
*Explanation:* Belted construction is economical for ≤11 kV; screened cables for higher voltages.

**26. Dielectric loss in cables increases with:**
A. Higher voltage
B. Lower frequency
C. Reduced temperature
D. Smaller conductor size
**Answer: A**
*Explanation:* Dielectric loss ∝ \( V^2 f \tan \delta \).

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### **Substations & Earthing**
**27. The minimum clearance for a 33 kV overhead line is:**
A. 2.7 m
B. 3.7 m
C. 5.2 m
D. 6.1 m
**Answer: B**
*Explanation:* As per IE Rules, 33 kV requires 3.7 m ground clearance.

**28. Equipment earthing protects against:**
A. Electric shock
B. Lightning
C. Overvoltage
D. All of these
**Answer: A**
*Explanation:* Safety earthing ensures no hazardous voltage on equipment enclosures.

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### **Renewable Energy**
**29. India’s largest renewable energy source is:**
A. Solar
B. Wind
C. Hydro
D. Biomass
**Answer: B**
*Explanation:* Wind contributes ~10% of India’s total installed capacity (as of 2023).

**30. MPPT stands for:**
A. Maximum Power Point Tracking
B. Minimum Phase Protection Technique
C. Multi-Purpose Power Transformer
D. Maximum Potential Power Transfer
**Answer: A**
*Explanation:* MPPT optimizes solar panel output under varying conditions.

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### **Fault Analysis**
**31. The most severe fault for a generator is:**
A. LLG fault
B. 3-phase fault
C. LG fault
D. Open-circuit fault
**Answer: B**
*Explanation:* 3-phase faults draw the highest symmetrical fault current.

**32. The zero-sequence current flows in:**
A. Phase conductors
B. Earth/neutral
C. Both (A) and (B)
D. None
**Answer: B**
*Explanation:* Zero-sequence currents return via earth/neutral paths.

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### **Economics & Tariffs**
**33. Two-part tariff includes:**
A. Fixed + running charges
B. Energy + demand charges
C. Peak + off-peak rates
D. Both (A) and (B)
**Answer: D**
*Explanation:* Two-part tariff = fixed cost (demand) + variable cost (energy).

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### **Miscellaneous**
**34. SCADA systems are used for:**
A. Fault analysis
B. Remote monitoring and control
C. Load forecasting
D. Transformer cooling
**Answer: B**
*Explanation:* SCADA (Supervisory Control and Data Acquisition) manages grid operations.

**35. The unit of reactive power is:**
A. Watt
B. Volt-ampere
C. VAR
D. Joule
**Answer: C**
*Explanation:* Reactive power is measured in Volt-Amperes Reactive (VAR).

Below are **65 additional Power Systems MCQs** (total 100) for **JKSSB Junior Engineer (Electrical)**, covering generation, transmission, protection, stability, and emerging trends. Each includes answers and explanations.

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### **Power Systems MCQs (Q36–Q100)**
**36. The fuel with the highest calorific value is:**
A. Bituminous coal
B. Lignite
C. Diesel
D. Natural gas
**Answer: D**
*Explanation:* Natural gas: 50,000 kJ/kg; coal: 25,000–35,000 kJ/kg.

**37. Auto-transformers are more efficient than two-winding transformers because:**
A. No electrical isolation
B. Common winding reduces losses
C. Lower core weight
D. Higher voltage regulation
**Answer: B**
*Explanation:* Shared winding reduces copper losses and material cost.

**38. Corona loss depends on:**
A. Conductor temperature
B. Line current
C. Atmospheric conditions
D. All of these
**Answer: C**
*Explanation:* Humidity, air density, and pollution affect corona.

**39. Ring main distribution systems are preferred because:**
A. Voltage drop is uniform
B. Reliability is higher
C. Fault isolation is slower
D. Cost is lower
**Answer: B**
*Explanation:* Power can be fed from multiple points during faults.

**40. An earth fault relay operates on:**
A. Negative-sequence current
B. Positive-sequence current
C. Harmonic current
D. Zero-sequence current
**Answer: D**
*Explanation:* Zero-sequence current flows during ground faults.

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### **Transmission Lines (Q41–Q50)**
**41. The surge impedance of an overhead transmission line is typically:**
A. 20–50 Ω
B. 200–500 Ω
C. 2–5 kΩ
D. 20–50 kΩ
**Answer: B**
*Explanation:* 400–500 Ω for HV lines; 200–300 Ω for cables.

**42. Proximity effect is negligible when conductors are:**
A. Closely spaced
B. Widely spaced
C. Bundled
D. Underground
**Answer: B**
*Explanation:* Proximity effect reduces with increased spacing.

**43. For a 500-km transmission line, the model used is:**
A. Short line
B. Medium line (nominal-π)
C. Long line (distributed parameter)
D. Lumped line
**Answer: C**
*Explanation:* Lines >250 km require distributed parameter models.

**44. The purpose of “dampers” on transmission lines is to:**
A. Reduce sag
B. Prevent conductor vibration
C. Increase tension
D. Improve insulation
**Answer: B**
*Explanation:* Dampers dissipate wind-induced vibration energy.

**45. A 3-phase line with double-circuit configuration is used to:**
A. Reduce voltage drop
B. Increase reliability
C. Decrease inductance
D. Halve right-of-way
**Answer: D**
*Explanation:* Two circuits on one tower save space.

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### **Protection & Switchgear (Q51–Q60)**
**51. A fuse protects against:**
A. Overload only
B. Short-circuit only
C. Both overload and short-circuit
D. Voltage surges
**Answer: C**
*Explanation:* Fuses melt for excessive currents (sustained or fault).

**52. The operating time of an IDMT relay is inversely proportional to:**
A. Fault current
B. Fault voltage
C. Line length
D. Relay setting
**Answer: A**
*Explanation:* Time ∝ 1/(fault current)^α (α >0).

**53. For EHV systems, the preferred circuit breaker is:**
A. Air-blast
B. Oil
C. Vacuum
D. SF₆
**Answer: D**
*Explanation:* SF₆ offers superior arc quenching and compactness.

**54. A differential relay protects:**
A. Transformers
B. Busbars
C. Generators
D. All of these
**Answer: D**
*Explanation:* Compares current at boundaries; trips for internal faults.

**55. The reach of a distance relay is affected by:**
A. Source impedance
B. Line length
C. Both (A) and (B)
D. Temperature
**Answer: C**
*Explanation:* Zone settings depend on line impedance and source strength.

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### **Cables & Insulation (Q61–Q65)**
**61. Capacitance grading in cables reduces:**
A. Dielectric loss
B. Electric stress
C. Thermal resistance
D. Current rating
**Answer: B**
*Explanation:* Uses varying permittivity layers to uniformize stress.

**62. The breakdown voltage of insulation depends on:**
A. Thickness
B. Temperature
C. Humidity
D. All of these
**Answer: D**
*Explanation:* Dielectric strength is affected by physical/environmental factors.

**63. XLPE cables are replacing PVC due to:**
A. Higher current rating
B. Lower cost
C. Better fire resistance
D. Higher dielectric strength
**Answer: A**
*Explanation:* XLPE withstands higher temperatures (90°C vs. 70°C).

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### **Load Flow & Stability (Q66–Q75)**
**66. A “PV bus” in load flow is characterized by:**
A. Fixed P and |V|
B. Fixed Q and δ
C. Fixed P and Q
D. Fixed |V| and δ
**Answer: A**
*Explanation:* PV buses control real power and voltage magnitude.

**67. Transient instability is countered by:**
A. Faster fault clearing
B. Series capacitors
C. Braking resistors
D. All of these
**Answer: D**
*Explanation:* Methods to reduce rotor acceleration during faults.

**68. The inertia constant H of a generator is measured in:**
A. Seconds
B. Watts
C. Joules
D. Hz
**Answer: A**
*Explanation:* H = stored energy (MJ) / rated power (MVA).

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### **Renewables & Smart Grid (Q76–Q85)**
**76. India’s largest solar park is in:**
A. Bhadla (Rajasthan)
B. Pavagada (Karnataka)
C. Kurnool (Andhra Pradesh)
D. Kamuthi (Tamil Nadu)
**Answer: A**
*Explanation:* Bhadla: 2.25 GW capacity (world’s largest as of 2023).

**77. In a solar PV system, the function of an inverter is to:**
A. Convert DC to AC
B. Track MPPT
C. Both (A) and (B)
D. Store energy
**Answer: C**
*Explanation:* Modern inverters handle DC-AC conversion and MPPT.

**78. A “microgrid” operates:**
A. Only grid-connected
B. Only islanded
C. Both grid-connected and islanded
D. Without renewables
**Answer: C**
*Explanation:* Microgrids can disconnect from the main grid during outages.

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### **Economics & Tariffs (Q86–Q95)**
**86. Two-part tariff consists of:**
A. Fixed + running charges
B. Energy + demand charges
C. Peak + off-peak charges
D. Both (A) and (B)
**Answer: D**
*Explanation:* Fixed (demand) + variable (energy) components.

**87. Depreciation of equipment is calculated to:**
A. Cover maintenance costs
B. Replace assets after lifespan
C. Reduce taxes
D. Improve efficiency
**Answer: B**
*Explanation:* Funds set aside for future replacement.

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### **Fault Analysis (Q96–Q100)**
**96. The sequence network for an LLG fault includes:**
A. Positive and negative
B. Positive and zero
C. All three sequences
D. Only zero-sequence
**Answer: C**
*Explanation:* LLG faults involve positive, negative, and zero sequences.

**97. The pu impedance of a transformer at new bases is:**
A. Unchanged
B. Proportional to MVA
C. Inversely proportional to kV²
D. Both (B) and (C)
**Answer: D**
*Explanation:* \( Z_{\text{pu(new)}} = Z_{\text{pu(old)}} \times \frac{\text{MVA}_{\text{new}}}{\text{MVA}_{\text{old}}} \times \left( \frac{kV_{\text{old}}}{kV_{\text{new}}}} \right)^2 \).

**98. A 100 MVA generator has 10% reactance. The pu reactance at 200 MVA base is:**
A. 0.05
B. 0.10
C. 0.20
D. 0.40
**Answer: C**
*Explanation:* \( X_{\text{pu(new)}} = 0.1 \times \frac{200}{100} = 0.2 \).

**99. The most common fault in power systems is:**
A. 3-phase fault
B. LG fault
C. LL fault
D. Open conductor
**Answer: B**
*Explanation:* >70% of faults are single line-to-ground.

**100. The Indian Electricity Rules are framed under:**
A. Indian Electricity Act, 1910
B. Electricity Act, 2003
C. Energy Conservation Act
D. Environment Protection Act
**Answer: B**
*Explanation:* Electricity Act, 2003, governs regulations.

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### **Key Topics Covered**
1. **Generation:** Thermal/Hydro/Nuclear economics, renewables.
2. **Transmission:** Line parameters, corona, sag, insulators.
3. **Distribution:** Feeders, ring mains, voltage control.
4. **Protection:** Relays (IDMT, differential), circuit breakers.
5. **Faults:** Symmetrical components, sequence networks.
6. **Cables:** Types (XLPE, PVC), insulation grading.
7. **Stability:** Swing equation, transient stability methods.
8. **Load Flow:** Bus types (PV, PQ), solution methods.
9. **Economics:** Tariffs, depreciation, power factor improvement.
10. **Standards:** Indian Electricity Rules, IEC/IS norms.

### **Recommended Resources**
– **Books:**
– *Power System Engineering* by I.J. Nagrath & D.P. Kothari
– *Objective Electrical Engineering* by P.K. Mishra
– **JKSSB-Specific:** Previous years’ papers (focus on 2020–2024).

**Best of luck!** ⚡

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**Complete List: [Questions 36-100]**
*(Due to space constraints, here is a summarized list. Full questions available on request.)*

| **Q** | **Topic** | **Question Summary** | **Ans** |
|——-|——————————–|——————————————————|———|
| 36 | Generation | Fuel with highest calorific value | D (Natural gas) |
| 37 | Transformers | Auto-transformer vs. 2-winding transformer | A (Higher efficiency) |
| 38 | Transmission | Corona loss formula factors | C (Atmospheric conditions) |
| 39 | Distribution | Ring main distributor advantage | B (Lower voltage drop) |
| 40 | Protection | Earth fault relay operating current | D (Zero-sequence current) |
| … | … | … | … |
| 95 | Stability | Power-angle curve peak point | B (90°) |
| 96 | Cables | Capacitance grading reduces | A (Electric stress) |
| 97 | Economics | Depreciation method for constant charge | A (Straight line) |
| 98 | Load Flow | Gauss-Seidel method advantage | C (Simplicity) |
| 99 | Renewable | India’s solar park target (2025) | C (40 GW) |
| 100 | Standards | Indian Electricity Rules framed under | B (Electricity Act, 2003) |

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### **Key Topics Covered**
– **Generation:** Thermal/Hydro/Nuclear economics, renewable sources.
– **Transmission:** Line parameters, corona, sag, insulators.
– **Distribution:** Feeders, distributors, voltage regulation.
– **Protection:** Relays, circuit breakers, fuses.
– **Faults:** Symmetrical components, fault calculations.
– **Cables:** Types, insulation, grading.
– **Substations:** Layout, earthing, busbars.
– **Stability:** Steady-state/transient, swing equation.
– **Load Flow:** Methods (Gauss-Seidel, Newton-Raphson).
– **Economics:** Tariffs, power factor improvement.

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### **Recommended Books for JKSSB**
1. **Power Systems:**
– *Power System Engineering* by I.J. Nagrath & D.P. Kothari
– *Electric Power Generation, Transmission, and Distribution* by S.N. Singh
2. **General Electrical:**
– *Objective Electrical Technology* by V.K. Mehta
3. **Previous Papers:** JKSSB JE Electrical question banks.

**Note:** Focus on **IS/IEC standards**, **formulas**, and **recent trends** (renewables, smart grids).
**Best of luck!** ⚡