Circuit Breakers / Power Quality (Needs Work)
Along the power lines and connections, we have the circuits though which electric power moves from one place to another. The quiz below is all about circuit breakers and how they work. All the best.
Questions and Answers
- 1.
What type of circuit breaker can carry the most current on a HV trans line 555 kv and higher?
- A.
SF6
- B.
Oil filled
- C.
Gas filled (Gas other than SF6? Or “Vacuum”?)
- D.
Air
Correct Answer
A. SF6Explanation
SF6 circuit breakers are the most suitable for carrying the highest current on a HV transmission line of 555 kV and higher. SF6, or sulfur hexafluoride, is a highly efficient and reliable insulating gas that allows for compact designs and high interrupting capabilities. It has excellent electrical insulation properties, high thermal conductivity, and arc-quenching ability. SF6 circuit breakers can handle large currents without overheating or damaging the equipment, making them the preferred choice for high voltage transmission lines.Rate this question:
-
- 2.
What is the medium used for circuit interruption used on a 555 kV circuit breaker?
- A.
Air-blast
- B.
SF6
- C.
Oil
- D.
Nitrogen
Correct Answer
B. SF6Explanation
SF6 (Sulfur Hexafluoride) is the medium used for circuit interruption in a 555 kV circuit breaker. SF6 is a highly effective and reliable insulating gas that has excellent electrical insulation properties. It is used in high-voltage circuit breakers because it allows for efficient and rapid interruption of electrical currents. SF6 gas is also non-toxic, non-flammable, and chemically stable, making it a safe choice for circuit interruption.Rate this question:
-
- 3.
In the High-end side of an Automatic Transfer Switch (ATS), what is not true in an Industrial Station?
- A.
ATS will transfer to an alternate circuit when there's a fault
- B.
ATS will protect the customer from transient power
- C.
ATS does not rely on battery
- D.
ATS will not transfer to an alternate circuit when there's a fault
Correct Answer
D. ATS will not transfer to an alternate circuit when there's a faultExplanation
The given answer states that in an Industrial Station, an Automatic Transfer Switch (ATS) will not transfer to an alternate circuit when there's a fault. This means that the ATS will not automatically switch to a backup circuit in case of a fault or failure in the primary circuit. This statement is not true because one of the main functions of an ATS is to provide seamless power transfer to an alternate circuit in the event of a fault or power outage in the primary circuit.Rate this question:
-
- 4.
A medium that is NOT used in power circuit breakers
- A.
Air break
- B.
SF6
- C.
Oil
- D.
CO2 gas
Correct Answer
D. CO2 gasExplanation
CO2 gas is not used in power circuit breakers because it does not have the necessary dielectric properties to effectively interrupt the flow of current. Power circuit breakers require a medium that can withstand high voltage and current levels without ionizing or breaking down. Air break, SF6, and oil are commonly used as dielectric mediums in power circuit breakers due to their high dielectric strength and ability to extinguish arcs. However, CO2 gas does not possess these properties and is therefore not suitable for use in power circuit breakers.Rate this question:
-
- 5.
Which is a characteristic of a circuit breaker?
- A.
Interrupting time = arcing time + opening time
- B.
Interrupting time = arcing time – opening time
- C.
Interrupting time = opening time – arcing time
- D.
None of the above
Correct Answer
A. Interrupting time = arcing time + opening timeExplanation
The correct answer is "Interrupting time = arcing time + opening time." This equation accurately represents the characteristic of a circuit breaker. The interrupting time, which is the time it takes for the circuit breaker to stop the flow of current, is equal to the sum of the arcing time and the opening time. The arcing time is the duration of the electrical arc that forms when the circuit is interrupted, and the opening time is the time it takes for the circuit breaker to physically open and break the circuit.Rate this question:
-
- 6.
At a temperature of 500 degrees Celsius in an oil filled equipment, the gas form is ----- in the absence of an arc
- A.
Methane
- B.
Hydrogen
- C.
Ethylene
- D.
Acetylene
Correct Answer
B. HydrogenExplanation
At a temperature of 500 degrees Celsius, in the absence of an arc, hydrogen gas is the most likely form to be present in an oil-filled equipment. This is because hydrogen has a low boiling point and is highly volatile, making it more likely to exist as a gas at high temperatures. Methane, ethylene, and acetylene have higher boiling points and are less likely to exist as gases at this temperature.Rate this question:
-
- 7.
See the following system schematic For a Fault at F and a circuit breaker / relay no operation at 4, what would be the operation of the circuit breaker for a backup relay?
- A.
7,9,8,6,5
- B.
1,2,3,10,6
- C.
5,8,9,10,6
Correct Answer
B. 1,2,3,10,6 -
- 8.
Symmetrical components have the most usage in
- A.
Single phase systems
- B.
3 phase balanced systems
- C.
3 phase unbalanced systems
Correct Answer
C. 3 phase unbalanced systemsExplanation
Symmetrical components are primarily used in 3 phase unbalanced systems. This is because symmetrical components allow for the analysis and understanding of the behavior of unbalanced systems by breaking them down into a set of balanced components. By doing so, it becomes easier to analyze and solve problems in unbalanced systems, such as identifying the causes of voltage or current imbalances and designing appropriate corrective measures. In contrast, single phase systems only have one phase and do not require symmetrical components for analysis, while 3 phase balanced systems have symmetrical voltages and currents, making the use of symmetrical components less necessary.Rate this question:
-
- 9.
In adjacent overlapping zones in the DWP 500-kv system, what component or device is normally overlapped?
- A.
Relay
- B.
Disconnect
- C.
Circuit breaker
- D.
Transformer
Correct Answer
C. Circuit breakerExplanation
In adjacent overlapping zones in the DWP 500-kv system, the component or device that is normally overlapped is the circuit breaker. Circuit breakers are used to protect electrical circuits from damage caused by overload or short circuits. In the case of overlapping zones, circuit breakers are installed in each zone to ensure that any faults or abnormalities in the electrical system can be isolated and controlled effectively. This overlapping arrangement helps to enhance the reliability and stability of the power transmission system.Rate this question:
-
- 10.
Adjacent protective zone for voltage below 500KV, the overlap usually occurs at
- A.
Circuit Breaker
- B.
Disconnect
- C.
Relay
- D.
Transformer
Correct Answer
A. Circuit BreakerExplanation
In a power system, the adjacent protective zone is designed to provide backup protection in case of a fault or abnormal condition. When the voltage is below 500KV, the overlap between protective zones typically occurs at the circuit breaker. The circuit breaker is responsible for interrupting the flow of current in the event of a fault, thereby protecting the system. By having the overlap at the circuit breaker, it ensures that any fault within the adjacent zone is quickly detected and cleared by tripping the circuit breaker, preventing further damage to the system.Rate this question:
-
- 11.
For transient stability, the most important factor is fast relaying
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Transient stability refers to the ability of a power system to maintain synchronism after a large disturbance, such as a fault or the sudden loss of a generator. Fast relaying plays a crucial role in detecting and isolating faults quickly. By rapidly disconnecting the faulty element, fast relaying helps to prevent cascading failures and stabilize the system. Therefore, in the context of transient stability, fast relaying is indeed the most important factor.Rate this question:
-
- 12.
Whats is the power factor of the circuit? What is the reactive power? What sized capacitor can be used to correct for this reactive power?
Correct Answer
0.65, 1.754, 80.761uFExplanation
Apparent Power = (9.615 A) (240 V) = 2.308kVA Power Factor= P/S Power Factor =1.5/2.308=.065
Reactive power= square root [Apparent power)^2 -(True power)^2]= Q=1.754
Q=E^2/Q X=E^2/Q X=(240^2)/(1.754kVAR) =X=32.845 X=1/(2pifC) C=1/(2pifX) =80.761ufRate this question:
- 13.
Which is the symbol for a ACB with a thermal tripping protection?
- A.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- B.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- C.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- D.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- E.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
Correct Answer
C.Explanation
The symbol for an ACB (Air Circuit Breaker) with thermal tripping protection is a rectangle with a diagonal line inside, representing the breaker, and a curved line above it, indicating the thermal tripping feature. This symbol is commonly used in electrical diagrams and schematics to represent this specific type of circuit breaker.Rate this question:
-
- 14.
Which symbol represents an ACB with a magnetic overload protection?
- A.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- B.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- C.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- D.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
Correct Answer
D.Explanation
The symbol that represents an ACB with a magnetic overload protection is a circuit breaker symbol with a small coil or zigzag line inside it. This coil represents the magnetic trip unit that detects overloads and trips the circuit breaker to protect the circuit from damage. The magnetic overload protection feature is commonly used in ACBs to provide additional protection against excessive current flow.Rate this question:
-
- 15.
Which is the symbol for a CB with a thermal/magnetic tripping protection?
- A.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- B.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- C.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- D.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
- E.
![Circuit Breakers / Power Quality (Needs Work) - Quiz]()
Correct Answer
A.Explanation
The symbol for a CB with a thermal/magnetic tripping protection is a combination of the symbols for a circuit breaker and a thermal/magnetic trip unit. It typically includes a rectangle with a diagonal line inside, representing the circuit breaker, and additional symbols such as a thermometer and a magnet, indicating the thermal and magnetic trip units respectively. This symbol is used to represent a circuit breaker that can trip based on both thermal and magnetic conditions.Rate this question:
-
- 16.
Which is the most severe fault on the department machine theory with respect to systematical components to solve the problem?
- A.
Single line to ground
- B.
Double line to ground
- C.
Three lines to ground
- D.
Line to line fault
Correct Answer
C. Three lines to groundExplanation
The most severe fault on the department machine theory with respect to systematical components to solve the problem is the "Three lines to ground" fault. This fault involves three lines being connected to the ground, which can cause significant damage to the system and result in a more severe problem compared to the other options listed.Rate this question:
-
- 17.
The momentary duty and the interrupting duty of a circuit breaker refers to:
- A.
No difference
- B.
The nominal and average short circuit current
- C.
The maximum short circuit current and the continuous short circuit current rating
- D.
The magnitude 0.5 to 1 cycle after a short circuit occurs and the magnitude of the current after 5 to 6 cycles
Correct Answer
D. The magnitude 0.5 to 1 cycle after a short circuit occurs and the magnitude of the current after 5 to 6 cyclesExplanation
The momentary duty and the interrupting duty of a circuit breaker refers to the magnitude of the current at different time intervals after a short circuit occurs. Momentary duty refers to the magnitude of the current 0.5 to 1 cycle after a short circuit occurs, while interrupting duty refers to the magnitude of the current after 5 to 6 cycles. This distinction is important in determining the capability of the circuit breaker to interrupt the short circuit current and protect the electrical system.Rate this question:
-
- 18.
The advantage of a breaker-and-a-half system versus a double breaker system is:
- A.
Lower Cost
- B.
Less complex relay protection
- C.
Greater reliability
- D.
Greater flexibility
Correct Answer
A. Lower CostExplanation
The advantage of a breaker-and-a-half system versus a double breaker system is lower cost. This means that implementing a breaker-and-a-half system is more cost-effective compared to a double breaker system.Rate this question:
-
- 19.
Is the highest load current that the circuit breaker is designed to carry for extended time periods:
- A.
Maximum Continuous Current
- B.
Maximum Interrupting Current
- C.
Interrupting Time
- D.
Closing Time
Correct Answer
A. Maximum Continuous CurrentExplanation
The highest load current that the circuit breaker is designed to carry for extended time periods is known as the Maximum Continuous Current. This refers to the maximum amount of current that the circuit breaker can handle without tripping or causing damage to the circuit. It is important to ensure that the load current does not exceed this value to maintain the safe and efficient operation of the circuit breaker.Rate this question:
-
- 20.
Circuit breakers are rated according to this:
- A.
Maximum Continuous Current
- B.
Maximum Interrupting Current
- C.
Interrupting Time
- D.
Closing Time
Correct Answer
B. Maximum Interrupting CurrentExplanation
Circuit breakers are rated according to the maximum interrupting current they can handle. This refers to the maximum amount of current that the circuit breaker can safely interrupt or stop in the event of a fault or overload. The higher the maximum interrupting current rating, the more capable the circuit breaker is at handling larger electrical currents and protecting the circuit from damage.Rate this question:
-
- 21.
Is the period from the instant current begins to flow through the trip coil until the circuit breaker interrupts the fault:
- A.
Maximum Continuous Current
- B.
Maximum Interrupting Current
- C.
Interrupting Time
- D.
Closing Time
Correct Answer
C. Interrupting TimeExplanation
The interrupting time refers to the period from the instant current starts flowing through the trip coil until the circuit breaker interrupts the fault. It is the time taken for the circuit breaker to open and stop the flow of current in the event of a fault. This time is crucial as it determines how quickly the circuit breaker can protect the system from potential damage caused by excessive current. A shorter interrupting time is generally preferred as it ensures faster response and minimizes the risk of damage.Rate this question:
-
- 22.
Is the time it takes to close a breaker from the instant the close coil is energized until current begins to flow through the breaker
- A.
Maximum Continuous Current
- B.
Maximum Interrupting Current
- C.
Interrupting Time
- D.
Closing Time
Correct Answer
D. Closing TimeExplanation
Closing time refers to the time it takes for a breaker to close and for current to start flowing through it after the close coil is energized. This is an important parameter to consider in electrical systems as it affects the overall response time and efficiency of the breaker. By knowing the closing time, operators can ensure that the breaker is functioning properly and that the current is flowing as intended.Rate this question:
-
- 23.
Which one do you like?
- A.
Option 1
- B.
Option 2
- C.
Option 3
- D.
Option 4
Correct Answer
A. Option 1 -
- 24.
The stability of an arc in a vacuum depends upon:
- A.
The contact material only
- B.
The contact material and its vapor pressure
- C.
The circuit parametersonly
- D.
A combination of both b & c
Correct Answer
D. A combination of both b & cExplanation
The stability of an arc in a vacuum depends on a combination of both the contact material and its vapor pressure, as well as the circuit parameters. The contact material affects the arc stability by determining the quality of the contact surface and its ability to withstand the heat generated by the arc. The vapor pressure of the contact material plays a role in determining the arc's stability by affecting the ionization and recombination processes within the arc. Additionally, the circuit parameters, such as the current and voltage levels, also influence the stability of the arc.Rate this question:
-
- 25.
Where voltages are high and current to be interrupted is low the preferred breaker is:
- A.
Air Blast CB
- B.
Oil CB
- C.
Vacuum CB
- D.
Any of the above
Correct Answer
C. Vacuum CBExplanation
In situations where voltages are high and the current to be interrupted is low, the preferred breaker is a Vacuum CB. This is because vacuum circuit breakers are specifically designed to handle high voltages and low currents. They use a vacuum as the arc quenching medium, which allows for efficient interruption of the electrical current without the need for any additional substances like oil or air. Vacuum CBs are also more reliable and require less maintenance compared to other types of circuit breakers. Therefore, in this scenario, a vacuum CB would be the most suitable choice.Rate this question:
-
- 26.
SF6 gas has excellent heat transfer properties because of its:
- A.
Higher molecular weight
- B.
Low gaseous viscosity
- C.
Higher dielectric strength
- D.
A combination of both a & b
Correct Answer
D. A combination of both a & bExplanation
The correct answer is a combination of both a & b. SF6 gas has excellent heat transfer properties due to its higher molecular weight and low gaseous viscosity. The higher molecular weight allows for more efficient heat transfer, while the low gaseous viscosity ensures smoother flow and less resistance, further enhancing heat transfer.Rate this question:
-
- 27.
The most suitable CB for a short line fault without switching resistor is:
- A.
Air BlastCB
- B.
M.O.CB
- C.
SF6
- D.
None
Correct Answer
C. SF6Explanation
SF6 (Sulfur Hexafluoride) is the most suitable circuit breaker for a short line fault without a switching resistor. SF6 circuit breakers are known for their high interrupting capacity and excellent arc quenching properties. They can effectively extinguish the arc generated during a short circuit fault, ensuring the safety of the electrical system. SF6 circuit breakers also have a compact design and require less maintenance compared to other types of circuit breakers. Therefore, SF6 is the most suitable choice for a short line fault without a switching resistor.Rate this question:
-
- 28.
For a lumped inductive load, with increase in supply frequency:
- A.
P and Q Increase
- B.
P increases Q decreased
- C.
P decreases Q increases
- D.
P & Q Decrease
Correct Answer
C. P decreases Q increasesExplanation
For a lumped inductive load, as the supply frequency increases, the inductive reactance also increases. This leads to a decrease in the active power (P) consumed by the load because the increase in inductive reactance causes a phase shift between the current and voltage, reducing the power factor. On the other hand, the reactive power (Q) consumed by the load increases because the inductive reactance is directly proportional to the reactive power. Therefore, P decreases and Q increases with an increase in supply frequency for a lumped inductive load.Rate this question:
-
- 29.
In case of a 3-phase short circuit in a system, the power fed into the system is:
- A.
Mostly reactive
- B.
Mostly active
- C.
Reactive only
- D.
Both equally
Correct Answer
A. Mostly reactiveExplanation
In a 3-phase short circuit, the power fed into the system is mostly reactive. This is because a short circuit occurs when there is a fault in the electrical system, causing a direct connection between the phases. As a result, the current flow increases significantly, leading to a high reactive power demand. Reactive power is required to establish and maintain the magnetic fields in the system, which is necessary for the operation of inductive loads such as motors and transformers. Therefore, during a short circuit, the power being fed into the system is primarily reactive in nature.Rate this question:
-
- 30.
Resistance switching is normally utilized in:
- A.
Bulky oil CBs
- B.
Minimum oil CBs
- C.
Air blast CBs
- D.
All types
Correct Answer
C. Air blast CBsExplanation
Resistance switching is normally utilized in air blast CBs. Air blast circuit breakers (CBs) are a type of circuit breaker that use a high-pressure air blast to extinguish the arc formed during circuit interruption. Resistance switching refers to the use of a resistor in the circuit to control the rate at which the circuit breaker contacts separate, allowing for a controlled and efficient interruption of the electrical current. This technique is commonly used in air blast CBs to ensure safe and effective circuit interruption.Rate this question:
-
- 31.
An RLC circuit remains predominantly inductive
- A.
At resonance frequency
- B.
Below resonance freq
- C.
Above resonance freq
- D.
At lower half power freq
Correct Answer
C. Above resonance freqExplanation
Above resonance frequency, the capacitive reactance of the circuit becomes dominant, causing the circuit to behave predominantly as a capacitive circuit. This means that the circuit's impedance decreases as the frequency increases, resulting in a higher current flow and a lower voltage across the circuit. Consequently, the circuit becomes less inductive and more capacitive at frequencies above resonance.Rate this question:
-
- 32.
The coefficient of reflection of a short circuited line is
- A.
1
- B.
-1
- C.
0
- D.
2
Correct Answer
B. -1Explanation
The coefficient of reflection of a short-circuited line is -1. This means that when a signal is sent down the line and reaches the short circuit, it is completely reflected back with a phase inversion. In other words, the amplitude of the reflected signal is equal to the amplitude of the incident signal, but with the opposite polarity. This is because a short circuit creates a low impedance path, causing the signal to be reflected without any loss or attenuation.Rate this question:
-
- 33.
If Pm is the maximum power transferred, the loss on the system is:
- A.
Pm / 4
- B.
Pm / 2
- C.
3 Pm / 4
- D.
None
Correct Answer
B. Pm / 2Explanation
The correct answer is Pm / 2. This is because in a system, the maximum power is transferred when the load impedance matches the complex conjugate of the source impedance. At this point, the power loss on the system is equal to half of the maximum power transferred. Therefore, the loss on the system is Pm / 2.Rate this question:
-
.png "See the following system schematic
For a Fault at F and a circuit breaker / relay no operation at 4, what would be the operation of the circuit breaker for a backup relay?")
.png "Whats is the power factor of the circuit?
What is the reactive power?
What sized capacitor can be used to correct for this reactive power?")
.png)
.png)
.png)
.png)
Quiz Review Timeline +
Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.
-
Current Version
-
Sep 05, 2023Quiz Edited by
ProProfs Editorial Team -
Sep 09, 2013Quiz Created by
Swiftdodgers
Back to top