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Questions and Answers
What is the role of an insulator in transmission lines?
What is the role of an insulator in transmission lines?
Insulators play an essential role in the operation of transmission lines by preventing current flow toward the earth.
What types of materials are commonly used in the electrical system for insulators?
What types of materials are commonly used in the electrical system for insulators?
Glass, ceramic, porcelain, PVC (Poly Vinyl Chloride), and polymers.
What kind of insulator is used in distribution systems?
What kind of insulator is used in distribution systems?
- Pin Insulator (correct)
- Shackle Insulator
- Suspension Insulator
- Strain Insulator
What is the voltage capacity of a pin insulator?
What is the voltage capacity of a pin insulator?
What type of insulator is used in overhead transmission lines?
What type of insulator is used in overhead transmission lines?
What is the purpose of grounding wires in a transmission line?
What is the purpose of grounding wires in a transmission line?
A ground wire is typically placed higher than the main conductors in a transmission line.
A ground wire is typically placed higher than the main conductors in a transmission line.
What does the protective angle refer to in the context of grounding wires?
What does the protective angle refer to in the context of grounding wires?
What is the function of a circuit breaker?
What is the function of a circuit breaker?
What type of circuit breaker is commonly used in domestic, commercial, and industrial settings?
What type of circuit breaker is commonly used in domestic, commercial, and industrial settings?
What are the main advantages of a vacuum circuit breaker?
What are the main advantages of a vacuum circuit breaker?
Why are SF6 circuit breakers not as commonly used as other types despite their high efficiency in arc quenching?
Why are SF6 circuit breakers not as commonly used as other types despite their high efficiency in arc quenching?
What is the general rule of thumb for determining the size of a circuit breaker for a single-phase supply?
What is the general rule of thumb for determining the size of a circuit breaker for a single-phase supply?
What are the main components of an electrical installation system?
What are the main components of an electrical installation system?
Copper, silver, and aluminum are considered good conductors of electricity.
Copper, silver, and aluminum are considered good conductors of electricity.
What is the primary purpose of insulators in an electrical installation system?
What is the primary purpose of insulators in an electrical installation system?
Armoured cables are typically used in underground installations due to their added protection.
Armoured cables are typically used in underground installations due to their added protection.
Trunking and conduit are both used to protect flex from damage and provide support.
Trunking and conduit are both used to protect flex from damage and provide support.
Modern appliances typically come with re-wireable plugs for safety.
Modern appliances typically come with re-wireable plugs for safety.
The maximum fuse size for a 3-pin plug in a domestic setting is 13 amps.
The maximum fuse size for a 3-pin plug in a domestic setting is 13 amps.
What type of switch is typically used for controlling a light fixture in multiple locations?
What type of switch is typically used for controlling a light fixture in multiple locations?
A plug socket can handle a continuous load of up to 3kW.
A plug socket can handle a continuous load of up to 3kW.
What is the purpose of a junction box in a wiring system?
What is the purpose of a junction box in a wiring system?
Pull cords are designed to be used in danger zones, such as bathrooms, to ensure that individuals do not have to touch electrical switches with wet hands.
Pull cords are designed to be used in danger zones, such as bathrooms, to ensure that individuals do not have to touch electrical switches with wet hands.
Which of the following is NOT considered an isolator?
Which of the following is NOT considered an isolator?
Flashcards
Ceramic Insulator
Ceramic Insulator
A material used to support overhead line conductors on poles, preventing current flow to the ground.
Suspension Insulator
Suspension Insulator
A type of insulator used in high-voltage transmission lines, comprising multiple discs. Offers high voltage capacity and flexibility.
Pin Insulator
Pin Insulator
An insulator used in distribution systems, generally up to 11kV, characterized by simple construction.
Strain Insulator
Strain Insulator
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Insulator Material Types
Insulator Material Types
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Maximum Voltage (Wooden Poles)
Maximum Voltage (Wooden Poles)
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Insulator Maintenance
Insulator Maintenance
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Transmission Line Tower
Transmission Line Tower
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Tower Grounding
Tower Grounding
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Grounding Wires
Grounding Wires
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Study Notes
Power Generation and Transmission
- Course: ELE-2303
- Date: Monday, July 1, 2024
- Course Objective: Describe different methods used for insulation and protection of transmission lines.
CLO3: Insulation and Protection of Transmission Lines
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3.1 Ceramic Insulator Characteristics:
- Material for medium voltage applications.
- Internal electric charge does not run freely (insulation).
- Supports overhead conductors, preventing current flow to earth.
- Different voltage ranges for varying distances (small, medium, long).
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3.1 Types of Insulators:
- Pin insulator: Used in distribution systems, 11kV voltage capacity, simple construction, low maintenance.
- Suspension insulator: Used in overhead transmission lines, offering flexibility and varying voltage capacity (11kV to 765kV), multiple disc design.
- Strain insulator: Similar to suspension type, used in overhead transmission but with variations, 33kV voltage capacity, placed in bends or other arm placements.
- Shackle Insulator: Small size, used in overhead distribution systems, 33kV voltage capacity, vertical or horizontal mounting.
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3.2 Maximum Voltage for Wooden Support Poles:
- Poles commonly used for 400V and 230V low tension lines.
- Lower cost compared to other poles.
- Foundation cost is comparable to wood pole.
- Long service life.
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3.3 Cleaning Insulators:
- Hot Line Washing: Cleaning insulators with water while electricity is on.
- White Vinegar: Removing water residue and weathering accumulation by soaking insulators overnight.
- Oxalic acid: Efficient, cheap cleaning agent for insulators.
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3.4 Transmission Line Tower Structure:
- Conductor swing considerations: Often in phase with wind. Minimum horizontal spacing should be at least 1% of span length.
- Ground clearances: Requirements for various voltages at different temperatures. (5.66 kV, 6.132kV, 7.220kV).
- Cable & power line spacing: Specific minimum clearances for different voltages.
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3.5 Grounding Wires and Tower Grounding:
- Bare conductors atop transmission towers to prevent lightning strikes.
- Parallel placement with main conductors.
- Grounded at each tower.
- Importance of mechanical strength, sufficient clearance from tower, and low footing resistance (under 10 ohms).
- Galvanized steel or ACSR (Aluminum Conductor Steel Reinforced) grounding wire.
- Protective angle (20° to 45°).
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3.6 Medium/High Voltage Circuit Breaker Components:
- Diagram showing the various components of the circuit breaker and their locations.
-
3.7 Circuit Breaker Types:
- Oil circuit breakers
- Vacuum circuit breakers
- Air blast circuit breakers
- SF6 circuit breakers
- Molded-case circuit breakers (MCCB)
- Miniature circuit breakers (MCB)
- Description and differentiation of circuit breaker types
-
3.8 Electrical Installation Systems Components:
- Description of the electrical components (conductors, insulators, cables, trunking, conduits, domestic 3-pin plugs, switches, sockets, junction boxes, pull cords,etc).
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Circuit Breaker Size Calculation (single-phase):
- Determining appropriate circuit breaker size based on calculations considering load type, cable material, environment temperature, and a 125% factor for the circuit current.
-
Circuit Breaker Size Calculation (three-phase): -Determining appropriate circuit breaker size based on three-phase calculations. The considerations of the load type and v3 factors are critical in this calculation.
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