All questions of Power Systems for Electrical Engineering (EE) Exam

Explanation:

Corona Discharge:
Corona discharge is a phenomenon that occurs when a high voltage is applied to a conductor with a very sharp point or edge, creating a faint glow or halo of light around the conductor. This glow is typically bluish in color.

Reason for Bluish Color:
- The bluish color of corona discharge is due to the excitation of nitrogen molecules in the air by the high voltage electric field.
- Nitrogen is the most abundant gas in the atmosphere and is responsible for producing the characteristic bluish glow.

Other Colors:
- While the typical color of corona discharge is bluish, it can also appear as purple or white depending on the composition of the surrounding gases and the intensity of the electric field.
- However, in general, corona discharge is most commonly observed as a bluish glow.

Importance of Color:
- The color of corona discharge can be used by engineers and technicians to diagnose problems in high voltage systems.
- By observing the color and intensity of the corona discharge, they can determine if there are any issues such as excessive electrical stress, insulation breakdown, or contamination.
In conclusion, corona discharge is generally bluish in color due to the excitation of nitrogen molecules in the air by the high voltage electric field. This bluish glow is a key characteristic of corona discharge and can provide valuable information about the condition of high voltage systems.

Understanding Surge Protectors
Surge protectors are crucial devices designed to protect electrical equipment from voltage spikes. To grasp why option 'C' is the correct answer, it's essential to understand how surge protectors function regarding impedance.
Impedance Characteristics
- Normal Voltage:
Surge protectors maintain a high impedance to normal operating voltage. This means that during regular conditions, they do not interfere with the electrical flow, allowing devices to function normally.
- Surge Voltage:
Conversely, surge protectors exhibit low impedance when a voltage surge occurs. This allows excess voltage to be diverted away from sensitive equipment, preventing damage.
Why Option 'C' is Correct
- High Impedance to Normal Voltage:
Surge protectors do not impede the normal voltage; hence, devices can operate efficiently without power loss or disruption.
- Low Impedance to Surge:
During a surge, the low impedance path enables the surge protector to channel the excess energy away, thereby protecting the connected devices.
Conclusion
In summary, surge protectors are designed to have high impedance under normal working conditions and low impedance during surges. This dual characteristic ensures the protection of electrical devices while maintaining their regular operation. Thus, option 'C' accurately represents the operational principles of surge protectors.

Introduction:
In the field of electrical engineering, circuit breakers are essential devices used to protect electrical systems from overloads, short circuits, and other electrical faults. When a fault occurs, such as a short circuit, a circuit breaker interrupts the flow of current to prevent damage to the system and ensure safety. There are various types of circuit breakers available, each with its own advantages and suitability for different applications.

The Most Suitable Circuit Breaker:
The most suitable circuit breaker for interrupting short line faults without resistance switching is the SF6 (sulfur hexafluoride) circuit breaker. This type of circuit breaker offers several advantages that make it ideal for this particular application:

1. High Dielectric Strength:
SF6 gas has excellent dielectric properties, meaning it can withstand high electric fields without ionizing. This characteristic allows SF6 circuit breakers to interrupt high-voltage faults effectively.

2. Self-Extinction:
When an arc is formed during a fault, SF6 gas rapidly absorbs the free electrons, preventing the arc from re-striking. This self-extinguishing property ensures that the circuit breaker can quickly and reliably interrupt the fault current.

3. Compact Design:
SF6 circuit breakers are compact in size, making them suitable for installations where space is limited. Their compact design also contributes to their high mechanical strength, making them resistant to vibrations and shocks.

4. Low Maintenance:
SF6 circuit breakers require minimal maintenance as compared to other types. The gas is non-toxic, non-flammable, and does not degrade over time. This characteristic eliminates the need for regular replacement or refilling of the gas.

5. High Operating Speed:
SF6 circuit breakers have high operating speeds, allowing them to interrupt faults quickly. This fast response time ensures that the fault current is interrupted promptly, minimizing damage to the electrical system.

Conclusion:
The SF6 circuit breaker is the most suitable option for interrupting short line faults without resistance switching. Its high dielectric strength, self-extinction capability, compact design, low maintenance requirements, and high operating speed make it an excellent choice for this application. Electrical engineers and system designers often prefer SF6 circuit breakers for their reliability and efficiency in protecting electrical systems from short circuit faults.

Supporting tower:
Wind pressure has a more predominant effect on supporting towers compared to other components of a transmission line system. Supporting towers are tall structures that bear the weight of the transmission lines and are exposed to the full force of wind. The wind exerts pressure on the tower, causing it to sway or vibrate. This can lead to structural fatigue and, in extreme cases, tower failure. Proper design and reinforcement of supporting towers are essential to ensure the stability and longevity of the transmission line system.

Neutral wires, Transmission lines, and Insulators:
While wind pressure can also impact neutral wires, transmission lines, and insulators, their design and placement are typically less affected by wind compared to supporting towers. Neutral wires are usually smaller in diameter and are designed to carry minimal current, so the impact of wind pressure on them is relatively minor. Transmission lines are often designed with sufficient clearance from the ground and other structures to minimize the effects of wind. Insulators are also designed to withstand mechanical stresses, including those caused by wind, but they are less susceptible to wind pressure compared to supporting towers.

In conclusion, supporting towers are the components of a transmission line system that are most affected by wind pressure. Proper design, maintenance, and reinforcement of supporting towers are crucial to ensure the reliability and safety of the transmission line system.

Interconnected System

An interconnected system refers to a distribution system where energy is distributed from two or more production plants through a feeder ring. This system is commonly used in electrical power systems to ensure reliability and redundancy in the supply of electricity. Let's explore the characteristics and advantages of an interconnected system.

Characteristics of an Interconnected System:

1. Feeder Ring: In an interconnected system, a feeder ring is used to distribute energy from multiple production plants. The feeder ring is a closed loop network that connects the production plants, allowing for the transfer of power between them.

2. Multiple Sources: The interconnected system utilizes two or more production plants as sources of energy. This arrangement ensures that if one plant experiences an outage or maintenance, the other plants can continue supplying power, ensuring uninterrupted electricity supply.

3. Redundancy: The use of multiple production plants in the interconnected system provides redundancy. If one plant fails, the other plants can compensate for the loss, ensuring a reliable supply of electricity to consumers.

Advantages of an Interconnected System:

1. Increased Reliability: The interconnected system enhances the reliability of the electrical distribution system by providing multiple sources of power. This reduces the chances of power outages and ensures uninterrupted electricity supply to consumers.

2. Flexibility: With an interconnected system, power can be easily transferred between production plants. This flexibility allows for load balancing and optimized utilization of available resources, leading to efficient operation of the electrical distribution system.

3. Load Sharing: The interconnected system enables load sharing among the production plants. When one plant is operating at maximum capacity, the excess load can be shifted to other plants, preventing overloading and ensuring that each plant operates within its safe limits.

4. Maintenance and Outage Management: An interconnected system allows for easier maintenance and outage management. If a production plant requires maintenance or experiences an outage, the load can be transferred to other plants without interrupting the supply to consumers.

Conclusion:

An interconnected system is a distribution system that utilizes a feeder ring to distribute energy from two or more production plants. This system enhances the reliability, flexibility, and efficiency of the electrical distribution system by providing redundancy, load sharing, and easy maintenance and outage management. It ensures uninterrupted power supply to consumers and is widely used in electrical power systems.

Introduction:
In electrical engineering, relays are widely used devices that control electrical circuits by opening and closing contacts electromechanically or electronically. They are classified based on various factors, including their constructional features. This question is asking us to identify the type of relay that is not based on constructional features.

Moving Iron Type Relay:
- Moving iron type relays have a movable iron armature and a fixed coil.
- The armature moves when the coil is energized, and this movement is used to open or close the contacts of the relay.
- These relays are commonly used for AC circuits and are suitable for both high and low currents.

Static Relay:
- Static relays do not have any moving parts.
- They use solid-state components such as transistors, diodes, and operational amplifiers to perform the relay function.
- Static relays are faster, more reliable, and have a longer lifespan compared to electromechanical relays.
- They are commonly used in applications where high-speed operation, precise control, and immunity to mechanical wear and tear are required.

Induction Relay:
- Induction relays use the principle of electromagnetic induction to operate.
- They consist of a coil and an iron core that create a magnetic field when energized.
- The magnetic field induces eddy currents in a conducting disc or a cup-shaped rotor, causing it to move and operate the relay contacts.
- Induction relays are commonly used in protective relaying applications, such as overcurrent and distance relays.

Current Relay:
- Current relay is not a specific type of relay based on constructional features.
- It is a generic term used to describe relays that operate based on the magnitude of current flowing through them.
- Current relays can be of various types, such as overcurrent relays, undercurrent relays, differential relays, etc.
- The constructional features of a current relay can vary depending on its specific application and design.

Conclusion:
Based on the above discussion, the correct answer is option 'D' - Current. Current relay is not a specific type of relay based on constructional features, but rather a general term used to describe relays that operate based on current magnitude. The other options, moving iron type relay, static relay, and induction relay, are all specific types of relays based on their constructional features.

Capacitance of the line:
The current in a transmission line under no load conditions is primarily due to the capacitance of the line. This capacitance allows for the storage of electric charge, which can result in a small current flow even when there is no external load connected to the line.

Explanation:
- When a transmission line is energized, the conductors and the insulating material between them form a capacitor.
- This capacitance allows for the accumulation of electric charge, creating an electric field between the conductors.
- Even in the absence of a load, this electric field can cause a small current to flow through the line due to the displacement of charges within the capacitance of the line.
- This current is typically very small and is known as the capacitive current.

Significance:
- The presence of capacitance in transmission lines can have implications for overall system performance and efficiency.
- It can impact the power factor of the system and can lead to losses in the form of reactive power.
- It is important for system operators to account for capacitance when designing and operating transmission lines to ensure optimal performance and efficiency.