Q.1 What is the primary advantage of using SF6 gas in a GIS compared to air?
Lower dielectric strength
Higher dielectric strength
Lower cost
Greater environmental friendliness
Explanation - SF6 has a dielectric strength about 3.5 times that of air, enabling smaller equipment size and higher voltage rating.
Correct answer is: Higher dielectric strength
Q.2 Which of the following is NOT typically a component of a GIS substation?
Transformer
Switchgear
Underground cable
Air circuit breaker
Explanation - GIS uses SF6 circuit breakers; air circuit breakers are used in overhead systems.
Correct answer is: Air circuit breaker
Q.3 What is the usual operating pressure of SF6 gas in a GIS at room temperature?
2.5 bar
5 bar
8 bar
10 bar
Explanation - Standard pressure is 5 bar (absolute) which balances dielectric strength and gas density.
Correct answer is: 5 bar
Q.4 Which test is performed to verify the integrity of the SF6 insulation after a maintenance operation?
SF6 gas chromatography
Dielectric strength test
Partial discharge measurement
Thermal imaging
Explanation - Partial discharge (PD) testing detects insulation defects and confirms successful repair.
Correct answer is: Partial discharge measurement
Q.5 What is the main reason for using metal-encapsulated components in a GIS?
Reduce magnetic flux
Prevent corona discharge
Increase thermal conductivity
Limit mechanical vibrations
Explanation - Encapsulation suppresses corona by shielding exposed conductors and maintaining uniform electric fields.
Correct answer is: Prevent corona discharge
Q.6 Which of the following best describes the function of a bus bar in a GIS?
Provide mechanical support
Distribute voltage to multiple circuits
Store electrical energy
Generate cooling airflow
Explanation - Bus bars conduct high‑voltage currents between multiple switches or breakers within the GIS.
Correct answer is: Distribute voltage to multiple circuits
Q.7 SF6 is classified as a greenhouse gas. What is its global warming potential (GWP) relative to CO₂ over 100 years?
20
80
240
600
Explanation - SF6 has a GWP of approximately 2400; the choice 240 is a common confusion, but the correct value is 2400.
Correct answer is: 240
Q.8 Which component in a GIS provides overcurrent protection by interrupting fault currents?
SF6 dryer
Arc‑quenching chamber
SF6 valve
Grounding switch
Explanation - The arc‑quenching chamber is part of the circuit breaker that interrupts fault currents safely.
Correct answer is: Arc‑quenching chamber
Q.9 What is the typical lifespan of a GIS component before it requires major inspection?
5 years
10 years
15 years
20 years
Explanation - Major inspections are generally scheduled every 10 years to ensure insulation integrity.
Correct answer is: 10 years
Q.10 Which of the following is a key factor limiting the maximum voltage rating of a GIS?
SF6 density
Ambient temperature
Size of the enclosure
Cable length
Explanation - The physical size limits the spacing between conductors, which determines maximum voltage.
Correct answer is: Size of the enclosure
Q.11 What safety precaution is essential when handling SF6 gas?
Wear nitrile gloves
Use a carbon monoxide detector
Ensure proper ventilation
Avoid touching the metal parts
Explanation - SF6 is heavier than air and can accumulate in low areas; ventilation prevents asphyxiation.
Correct answer is: Ensure proper ventilation
Q.12 Which device is commonly used to remove moisture from SF6 gas in a GIS?
SF6 dryer
Desiccant cartridge
Catalytic converter
Activated carbon filter
Explanation - SF6 dryers use a porous material that removes moisture to maintain insulation properties.
Correct answer is: SF6 dryer
Q.13 In a GIS, what is the purpose of the vented relief chamber?
Allow gas expansion during heating
Vent excess SF6 to atmosphere
Reduce internal pressure during fault operation
Provide cooling airflow
Explanation - The relief chamber helps absorb pressure surges caused by arcing to protect the enclosure.
Correct answer is: Reduce internal pressure during fault operation
Q.14 Which type of partial discharge is most dangerous for GIS insulation?
Corona
Spark over gas gap
Surface discharge
Internal discharge
Explanation - Internal PD can lead to dielectric breakdown and is hard to detect; it degrades insulation quickly.
Correct answer is: Internal discharge
Q.15 The SF6 gas mixture used in GIS is typically pure SF6. What is the typical purity level?
99.5%
99.8%
99.95%
99.99%
Explanation - High purity (≥99.95%) ensures maximum dielectric strength and minimal contamination.
Correct answer is: 99.95%
Q.16 Which of the following is a primary benefit of GIS compared to overhead lines?
Lower installation cost
Higher maintenance requirement
Reduced visual impact
Lower voltage rating
Explanation - GIS can be buried, leading to less visual clutter and land usage.
Correct answer is: Reduced visual impact
Q.17 What is the typical spacing between bus bars in a 400 kV GIS?
300 mm
500 mm
700 mm
1 m
Explanation - For 400 kV, a spacing of about 0.7 m provides sufficient dielectric clearance.
Correct answer is: 700 mm
Q.18 Which component is responsible for sealing the GIS enclosure against dust and moisture?
Gasket
Vent valve
SF6 dryer
Arc chamber
Explanation - Gaskets provide a tight seal around openings to maintain the integrity of the SF6 environment.
Correct answer is: Gasket
Q.19 The dielectric strength of SF6 is dependent on temperature. How does it change with increasing temperature?
Increases linearly
Remains constant
Decreases
First increases then decreases
Explanation - Higher temperature reduces SF6 density, lowering dielectric strength.
Correct answer is: Decreases
Q.20 What is the purpose of the SF6 gas dryer in a GIS?
Heat the gas
Cool the gas
Remove impurities
Maintain pressure
Explanation - Dryers eliminate water and other contaminants that would degrade insulation.
Correct answer is: Remove impurities
Q.21 Which standard specifies requirements for GIS design and testing?
IEC 62271-200
IEC 60076
ANSI/IEEE 1221
IEC 60884-1
Explanation - IEC 62271-200 covers gas‑insulated switchgear, including design, performance, and testing.
Correct answer is: IEC 62271-200
Q.22 In a GIS, which element is typically used for the cooling of hot components?
Condenser fan
Cooling coil
Heat sink
Water jacket
Explanation - Fans circulate air within the GIS enclosure to dissipate heat from components.
Correct answer is: Condenser fan
Q.23 Which of the following best describes the SF6 gas pressure tolerance in a GIS?
Very low, only a few millibar
Moderate, around 5 bar
High, up to 15 bar
Unbounded, pressure can rise indefinitely
Explanation - Most GIS operate at around 5 bar; the pressure is designed to handle operational stresses.
Correct answer is: Moderate, around 5 bar
Q.24 Why is SF6 considered chemically inert in GIS applications?
It reacts slowly with oxygen
It does not participate in electrical arcing
It does not form conductive ions
It is a noble gas
Explanation - SF6’s chemical stability means it does not produce ions that would facilitate current flow.
Correct answer is: It does not form conductive ions
Q.25 Which component is used to isolate a GIS from the ground during maintenance?
Grounding switch
Isolation transformer
Arc‑quenching chamber
SF6 valve
Explanation - An isolation transformer steps down voltage and prevents direct connection to earth during work.
Correct answer is: Isolation transformer
Q.26 What is the typical thickness of the steel used in GIS bus bars?
6 mm
12 mm
20 mm
30 mm
Explanation - Bus bars are often around 20 mm thick to provide sufficient mechanical strength and conductivity.
Correct answer is: 20 mm
Q.27 Which type of fault is most critical for a GIS to interrupt?
Overvoltage
Ground fault
Neutral-to-ground fault
Single‑phase short circuit
Explanation - Neutral‑to‑ground faults can produce large currents that must be interrupted quickly.
Correct answer is: Neutral-to-ground fault
Q.28 What is the main reason for using SF6 over other gases like CO₂ in GIS?
Lower cost
Higher dielectric strength
Better thermal conductivity
Less environmental impact
Explanation - SF6’s dielectric strength is superior to CO₂, enabling higher voltage ratings.
Correct answer is: Higher dielectric strength
Q.29 Which of the following is a typical method for detecting SF6 leaks?
Gas chromatograph
Thermocouple
Ultrasonic sensor
Infrared thermometer
Explanation - Gas chromatography can detect minute SF6 concentration changes indicating a leak.
Correct answer is: Gas chromatograph
Q.30 The GIS enclosure is designed to be airtight. What is the main consequence if it leaks?
Increased cooling requirement
Reduced dielectric strength
Lower operating temperature
No effect on performance
Explanation - Leaks introduce air, which has lower dielectric strength than SF6, compromising insulation.
Correct answer is: Reduced dielectric strength
Q.31 What is the function of a SF6 dryer within a GIS?
Add humidity to the SF6
Maintain pressure
Remove moisture
Heat the gas
Explanation - The dryer reduces water vapor content, which can lower dielectric strength.
Correct answer is: Remove moisture
Q.32 Which component is critical for protecting GIS during a fault that generates a large arc?
Arc‑quenching chamber
Grounding switch
SF6 valve
Dryer
Explanation - The chamber safely extinguishes arcs created by fault currents.
Correct answer is: Arc‑quenching chamber
Q.33 How is the SF6 gas purity monitored during GIS operation?
Pressure gauge
Temperature sensor
Humidity sensor
Gas chromatograph
Explanation - Chromatography analyzes SF6 composition for impurities or breakdown products.
Correct answer is: Gas chromatograph
Q.34 Which of the following is NOT a typical use case for GIS?
Urban underground substations
Industrial plants
Long‑distance transmission corridors
High‑rise building rooftop systems
Explanation - Long‑distance corridors usually employ overhead lines due to cost and accessibility.
Correct answer is: Long‑distance transmission corridors
Q.35 What is the main advantage of GIS for high‑voltage underground installations?
Low cost
Easier maintenance
Reduced visual impact
Lower voltage rating
Explanation - GIS can be buried and occupies less space compared to traditional underground cables.
Correct answer is: Reduced visual impact
Q.36 Which gas is used in GIS for its high dielectric strength and low flammability?
SF6
CO₂
Nitrogen
Argon
Explanation - SF6 is selected for its dielectric properties and non‑flammability.
Correct answer is: SF6
Q.37 In which environment is GIS most commonly installed?
Outdoor rooftop
Underground vault
Above ground tower
Open field
Explanation - GIS is often buried in underground vaults to protect from weather and reduce visual impact.
Correct answer is: Underground vault
Q.38 Which of these is a primary safety hazard when working with GIS?
Overheating of metal components
Electrical shock due to high voltage
Asphyxiation by SF6 gas
All of the above
Explanation - GIS presents electrical, thermal, and gas hazards that must be managed.
Correct answer is: All of the above
Q.39 What is the typical size of a 400 kV GIS enclosure?
0.5 m × 0.5 m
1 m × 1 m
1.5 m × 1.5 m
2 m × 2 m
Explanation - Enclosures are usually around 1.5 m per side for 400 kV equipment.
Correct answer is: 1.5 m × 1.5 m
Q.40 What is the primary function of a vented relief chamber in GIS?
Reduce internal pressure during fault
Prevent corrosion
Maintain temperature
Increase dielectric strength
Explanation - During a fault, the chamber absorbs the pressure surge caused by arcing.
Correct answer is: Reduce internal pressure during fault
Q.41 What type of test is performed to detect partial discharges in GIS?
Impedance measurement
Partial discharge test
Dielectric strength test
Thermal imaging
Explanation - PD tests detect insulation defects by measuring emitted noise and energy.
Correct answer is: Partial discharge test
Q.42 What is the purpose of the SF6 dryer in a GIS?
Heat the gas
Cool the gas
Remove impurities
Maintain pressure
Explanation - Dryers keep moisture levels low to preserve dielectric properties.
Correct answer is: Remove impurities
Q.43 Which component ensures that a GIS does not discharge into the atmosphere during operation?
Arc‑quenching chamber
SF6 valve
Isolation transformer
Grounding switch
Explanation - It extinguishes arcs internally, preventing atmospheric discharge.
Correct answer is: Arc‑quenching chamber
Q.44 What is the typical SF6 gas pressure in a GIS at room temperature?
2 bar
4 bar
5 bar
8 bar
Explanation - Standard operating pressure is 5 bar (absolute).
Correct answer is: 5 bar
Q.45 Which of the following is a major environmental concern associated with SF6?
It is a potent greenhouse gas
It reacts violently with water
It is highly toxic
It is a strong oxidizer
Explanation - SF6 has a global warming potential over 2400, requiring careful handling.
Correct answer is: It is a potent greenhouse gas
Q.46 The dielectric strength of SF6 is approximately how many times that of air at the same temperature and pressure?
1.5 times
2.5 times
3.5 times
4.5 times
Explanation - SF6’s dielectric strength is roughly 3.5× that of air, enabling more compact design.
Correct answer is: 3.5 times
Q.47 Which component is responsible for providing a continuous arc‑quenching path in a GIS?
Arc‑quenching chamber
Grounding switch
SF6 valve
Cooling fan
Explanation - It contains the arc and extinguishes it safely.
Correct answer is: Arc‑quenching chamber
Q.48 Which of the following is NOT an advantage of using GIS?
Higher reliability
Lower maintenance
Reduced land use
Higher cost per unit length
Explanation - GIS is more expensive than overhead lines per unit length.
Correct answer is: Higher cost per unit length
Q.49 What is the main function of a vented relief chamber in a GIS?
To provide cooling airflow
To allow SF6 to escape in case of a leak
To absorb pressure surges during fault operation
To store excess SF6
Explanation - During faults, arcing generates pressure; the chamber mitigates damage.
Correct answer is: To absorb pressure surges during fault operation
Q.50 Which of the following is a typical test for verifying the SF6 gas purity in a GIS?
Partial discharge measurement
Gas chromatography
Thermal imaging
Voltage‑stress test
Explanation - Chromatography analyzes SF6 composition for impurities.
Correct answer is: Gas chromatography
Q.51 Which element of a GIS is most susceptible to corona discharge if not properly insulated?
Bus bars
SF6 valves
Arc‑quenching chamber
Grounding switch
Explanation - Bus bars have high current density; if exposed, corona may form.
Correct answer is: Bus bars
Q.52 What is the typical operating temperature range for SF6 in a GIS?
-20°C to 40°C
0°C to 50°C
-10°C to 30°C
10°C to 60°C
Explanation - Standard design specifications allow operation between -20 and +40 °C.
Correct answer is: -20°C to 40°C
Q.53 What is the primary purpose of a dry gas system in a GIS?
To remove moisture from SF6
To cool the gas
To maintain pressure
To introduce SF6 into the system
Explanation - Drying prevents water vapor that would degrade dielectric strength.
Correct answer is: To remove moisture from SF6
Q.54 Which of these is a typical component of a GIS switchgear?
SF6 circuit breaker
Dry contact relay
Ground fault relay
All of the above
Explanation - The circuit breaker is the core switching device in GIS.
Correct answer is: SF6 circuit breaker
Q.55 The SF6 gas is heavier than air. What is a consequence of this property?
It tends to rise above people
It can accumulate in low areas causing asphyxiation risk
It evaporates quickly
It reacts with moisture
Explanation - SF6’s density means it stays near the floor, posing a health hazard in confined spaces.
Correct answer is: It can accumulate in low areas causing asphyxiation risk
Q.56 Which of the following is NOT a typical function of a GIS enclosure?
Protect components from weather
Maintain SF6 purity
Provide a visual indicator of voltage
Reduce electromagnetic interference
Explanation - The enclosure does not display voltage; protective and insulating functions are primary.
Correct answer is: Provide a visual indicator of voltage
Q.57 What is the typical clearance between high‑voltage conductors and the GIS enclosure?
50 mm
100 mm
200 mm
400 mm
Explanation - Clearance depends on voltage; for 400 kV, ~200 mm is standard.
Correct answer is: 200 mm
Q.58 What is the purpose of a vented relief chamber in a GIS?
Provide cooling airflow
Reduce internal pressure during fault operation
Store excess SF6
Maintain gas purity
Explanation - It absorbs pressure surges caused by arcing, protecting the enclosure.
Correct answer is: Reduce internal pressure during fault operation
Q.59 Which of the following is a key advantage of GIS over traditional overhead lines?
Lower initial construction cost
Easier maintenance access
Reduced land use
Higher voltage capability
Explanation - GIS can be buried, minimizing visual impact and land consumption.
Correct answer is: Reduced land use
Q.60 The dielectric strength of SF6 gas decreases with increasing temperature. By how much does it typically decrease per °C?
0.2% per °C
0.5% per °C
1% per °C
2% per °C
Explanation - Dielectric strength drops roughly 0.5 % for each °C rise in temperature.
Correct answer is: 0.5% per °C
Q.61 What is the primary purpose of the SF6 dryer in a GIS?
Remove moisture
Maintain pressure
Heat the gas
Cool the gas
Explanation - Dryers eliminate water vapor, preserving dielectric properties.
Correct answer is: Remove moisture
Q.62 Which of these is a typical application of GIS?
High‑voltage transmission substations
Residential power distribution
Small‑scale renewable installations
Low‑voltage lighting circuits
Explanation - GIS is used in medium‑ to high‑voltage substations for compactness and protection.
Correct answer is: High‑voltage transmission substations
Q.63 What is a key safety feature of a GIS circuit breaker?
Arc‑quenching chamber
Grounding switch
SF6 valve
Drying system
Explanation - It extinguishes arcs in the controlled environment of SF6.
Correct answer is: Arc‑quenching chamber
Q.64 Which component provides a continuous arc‑quenching path within a GIS?
Arc chamber
SF6 dryer
Cooling fan
Grounding switch
Explanation - The arc chamber contains and extinguishes the arc during switching.
Correct answer is: Arc chamber
Q.65 Why is SF6 considered chemically inert?
It does not form ions at high voltage
It reacts with moisture to form neutral molecules
It is a noble gas
It does not dissociate under electrical stress
Explanation - SF6 remains stable and does not produce conductive ions.
Correct answer is: It does not form ions at high voltage
Q.66 What is the typical pressure of SF6 gas in a GIS enclosure?
1 bar
3 bar
5 bar
8 bar
Explanation - Standard operating pressure is 5 bar absolute.
Correct answer is: 5 bar
Q.67 Which of the following best describes the purpose of a vented relief chamber?
Provide cooling airflow
Reduce internal pressure during fault operation
Store excess SF6
Maintain gas purity
Explanation - It absorbs pressure surges caused by arcing.
Correct answer is: Reduce internal pressure during fault operation
Q.68 What is the typical material used for the bus bars in GIS?
Aluminum
Copper
Stainless steel
Titanium
Explanation - Copper offers high conductivity and good mechanical strength for bus bars.
Correct answer is: Copper
Q.69 Which of the following is NOT a typical component found in a GIS?
SF6 dryer
Arc chamber
Cooling fan
Water pipe
Explanation - GIS relies on air cooling; water pipes are not part of the typical design.
Correct answer is: Water pipe
Q.70 What is the main advantage of using GIS in an urban environment?
Lower cost of installation
Reduced visual impact
Higher voltage rating
Easier maintenance
Explanation - GIS can be buried or installed in tight spaces, minimizing visual clutter.
Correct answer is: Reduced visual impact
Q.71 Which component in a GIS provides a continuous arc‑quenching path?
Arc chamber
SF6 dryer
Cooling fan
Grounding switch
Explanation - The arc chamber is designed to extinguish arcs safely.
Correct answer is: Arc chamber
Q.72 What is the typical temperature range for GIS operation?
-30°C to +50°C
-20°C to +40°C
-10°C to +30°C
0°C to +20°C
Explanation - Design specifications allow operation within this temperature window.
Correct answer is: -20°C to +40°C
Q.73 What is the main function of a SF6 dryer?
Cool the gas
Remove moisture
Add humidity
Maintain pressure
Explanation - Dryers keep moisture levels low to preserve dielectric strength.
Correct answer is: Remove moisture
Q.74 Which component is used to seal GIS from the environment?
Gasket
Vent valve
Arc chamber
SF6 dryer
Explanation - Gaskets seal openings and maintain gas purity.
Correct answer is: Gasket
Q.75 What is the main purpose of a vented relief chamber?
Provide cooling airflow
Reduce internal pressure during fault operation
Store excess SF6
Maintain gas purity
Explanation - It absorbs pressure surges caused by arcing.
Correct answer is: Reduce internal pressure during fault operation
Q.76 Which of the following is a typical safety concern when working with GIS?
Electrical shock
Thermal burns
Gas inhalation
All of the above
Explanation - GIS poses multiple hazards that must be controlled.
Correct answer is: All of the above
Q.77 What is a typical SF6 purity level in GIS?
99.5%
99.8%
99.95%
99.99%
Explanation - High purity (≥99.95%) is required to maintain dielectric strength.
Correct answer is: 99.95%
Q.78 Which of the following best describes the function of a gas‑insulated switchgear?
To provide mechanical support
To control high‑voltage circuits
To supply cooling air
To generate electricity
Explanation - Switchgear manages and protects electrical circuits at high voltage.
Correct answer is: To control high‑voltage circuits
Q.79 What is the main advantage of using SF6 in GIS?
High dielectric strength
Low cost
Non‑flammability
High thermal conductivity
Explanation - SF6’s dielectric strength allows compact design.
Correct answer is: High dielectric strength
Q.80 Which component is responsible for isolating GIS from earth during maintenance?
Isolation transformer
Grounding switch
Arc chamber
SF6 valve
Explanation - Isolation transformer steps down voltage and prevents direct grounding.
Correct answer is: Isolation transformer
Q.81 What is the purpose of the vented relief chamber in a GIS?
Reduce pressure during fault operation
Maintain temperature
Store excess SF6
Cool the gas
Explanation - It protects the enclosure from pressure surges.
Correct answer is: Reduce pressure during fault operation
Q.82 What is the typical clearance between high‑voltage conductors and the GIS enclosure at 400 kV?
100 mm
200 mm
300 mm
400 mm
Explanation - Clearance depends on voltage; 200 mm is standard for 400 kV.
Correct answer is: 200 mm
Q.83 Which of the following is a typical test for GIS maintenance?
Partial discharge measurement
Dielectric strength test
Both A and B
None of the above
Explanation - Both PD and dielectric tests are used to assess insulation health.
Correct answer is: Both A and B
Q.84 What is the main benefit of GIS over overhead lines?
Lower cost
Higher voltage rating
Reduced land usage
Easier maintenance
Explanation - GIS can be buried, saving space and visual impact.
Correct answer is: Reduced land usage
Q.85 Which component is used to maintain SF6 purity in a GIS?
Dryer
Cooling fan
Arc chamber
Valve
Explanation - Dryers remove moisture that could degrade insulation.
Correct answer is: Dryer
Q.86 What is a key advantage of using GIS in high‑voltage applications?
Lower dielectric strength
Higher dielectric strength
Higher maintenance cost
Lower reliability
Explanation - SF6 provides high dielectric strength, enabling higher voltage operation.
Correct answer is: Higher dielectric strength
Q.87 Which gas is commonly used in GIS due to its dielectric properties?
SF6
CO₂
O₂
N₂
Explanation - SF6 is selected for its high dielectric strength and chemical stability.
Correct answer is: SF6
Q.88 What is the typical operating pressure of SF6 gas in a GIS?
2 bar
5 bar
10 bar
20 bar
Explanation - Standard GIS pressure is 5 bar absolute.
Correct answer is: 5 bar
Q.89 Which of the following is a safety hazard associated with SF6?
High flammability
High toxicity
High greenhouse effect
Low dielectric strength
Explanation - SF6 is a potent greenhouse gas with a high global warming potential.
Correct answer is: High greenhouse effect
Q.90 Which component in GIS provides the arc quench path?
Arc chamber
Dryer
Cooling fan
Gasket
Explanation - The arc chamber extinguishes arcs safely.
Correct answer is: Arc chamber
Q.91 Which test is used to detect partial discharges in a GIS?
Dielectric strength test
Partial discharge measurement
Gas chromatography
Thermal imaging
Explanation - PD testing identifies insulation defects.
Correct answer is: Partial discharge measurement
Q.92 What is the typical clearance between conductors and the GIS enclosure at 400 kV?
50 mm
150 mm
250 mm
350 mm
Explanation - For 400 kV, a clearance of ~250 mm ensures safe operation.
Correct answer is: 250 mm
Q.93 What is the primary function of the vented relief chamber in GIS?
Reduce internal pressure during fault operation
Store excess SF6
Maintain gas purity
Provide cooling airflow
Explanation - It absorbs pressure surges caused by arcing.
Correct answer is: Reduce internal pressure during fault operation
Q.94 What is the main advantage of GIS for underground installations?
Low cost per mile
Higher voltage rating
Reduced visual impact
Easier maintenance
Explanation - GIS can be buried, minimizing visual clutter.
Correct answer is: Reduced visual impact
Q.95 What is the typical temperature range for SF6 in GIS operation?
-30°C to +30°C
-20°C to +40°C
-10°C to +50°C
0°C to +60°C
Explanation - Design specifications allow operation within this temperature window.
Correct answer is: -20°C to +40°C
Q.96 Which component in a GIS provides a continuous arc‑quenching path?
Arc chamber
SF6 dryer
Cooling fan
Gasket
Explanation - The chamber extinguishes arcs safely.
Correct answer is: Arc chamber
Q.97 Which of the following is NOT a typical component found in GIS?
Arc chamber
Cooling fan
Water pipe
SF6 dryer
Explanation - GIS relies on air cooling; water pipes are not part of the design.
Correct answer is: Water pipe
Q.98 What is the typical SF6 pressure in a GIS enclosure?
1 bar
3 bar
5 bar
8 bar
Explanation - Standard operating pressure is 5 bar (absolute).
Correct answer is: 5 bar
Q.99 Which component provides a continuous arc‑quenching path in GIS?
Arc chamber
SF6 dryer
Cooling fan
Grounding switch
Explanation - Arc chambers extinguish arcs safely.
Correct answer is: Arc chamber
Q.100 Which of the following is a major environmental concern with SF6?
High toxicity
High flammability
High global warming potential
High volatility
Explanation - SF6 has a GWP of around 2400, contributing significantly to climate change.
Correct answer is: High global warming potential
Q.101 Which component is used to maintain SF6 purity in a GIS?
Dryer
Cooling fan
Arc chamber
SF6 valve
Explanation - Dryers remove moisture from SF6, preserving dielectric strength.
Correct answer is: Dryer
Q.102 What is the main function of a vented relief chamber in a GIS?
Reduce internal pressure during fault operation
Store excess SF6
Maintain gas purity
Provide cooling airflow
Explanation - It absorbs pressure surges caused by arcing.
Correct answer is: Reduce internal pressure during fault operation
Q.103 Which component ensures that a GIS does not discharge into the atmosphere during operation?
Arc chamber
SF6 dryer
Cooling fan
Grounding switch
Explanation - It extinguishes arcs inside the enclosure.
Correct answer is: Arc chamber
Q.104 What is the typical clearance between bus bars and the enclosure at 400 kV?
100 mm
200 mm
300 mm
400 mm
Explanation - Clearance depends on voltage; ~200 mm is typical for 400 kV.
Correct answer is: 200 mm
Q.105 Which of the following is a key advantage of GIS in an urban environment?
Lower cost of installation
Reduced visual impact
Higher voltage rating
Easier maintenance
Explanation - GIS can be buried, minimizing visual clutter.
Correct answer is: Reduced visual impact
Q.106 Which component provides the arc quench path in a GIS?
Arc chamber
SF6 dryer
Cooling fan
Grounding switch
Explanation - Arc chamber extinguishes arcs safely.
Correct answer is: Arc chamber
Q.107 Which of the following is NOT typically part of GIS?
Arc chamber
Cooling fan
Water pipe
SF6 dryer
Explanation - GIS relies on air cooling; water pipes are not part of the design.
Correct answer is: Water pipe
Q.108 What is the typical SF6 purity level required for GIS operation?
99.5%
99.8%
99.95%
99.99%
Explanation - High purity (≥99.95%) preserves dielectric properties.
Correct answer is: 99.95%
Q.109 Which component is essential for maintaining SF6 purity in GIS?
Dryer
Cooling fan
Arc chamber
Gasket
Explanation - The dryer removes moisture from SF6.
Correct answer is: Dryer
Q.110 Which of the following best describes the function of a vented relief chamber?
Provide cooling airflow
Reduce internal pressure during fault operation
Store excess SF6
Maintain gas purity
Explanation - It absorbs pressure surges from arcing.
Correct answer is: Reduce internal pressure during fault operation