Electrical Engineering: Cables and Protection Systems

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What is the primary purpose of a voltage stabilizer?

To maintain a stable output voltage (correct)
To increase voltage levels
To automate the control of electrical systems
To measure electrical consumption

Which property of cables is most critical for ensuring safety in high-temperature environments?

Current carrying capacity
Flexibility
Fire resistance (correct)
Cost-effectiveness

What factor is NOT essential when selecting cables for specific applications?

Conductor size
Current carrying capacity
Voltage rating
Color of the insulation (correct)

What characteristic makes copper conductors preferable over aluminum in most applications?

Better conductivity (C) Signup and view all the answers

Which type of insulation material is best suited for environments with frequent bending?

Rubber (D) Signup and view all the answers

What is the primary purpose of insulation in electrical wiring?

To prevent electrical leakage and ensure safety (B) Signup and view all the answers

Which component serves as a central distribution point for incoming power in an LT system?

Main Distribution Board (A) Signup and view all the answers

What type of switch is specifically designed to disconnect a circuit for maintenance or safety?

Isolator (B) Signup and view all the answers

Which of the following circuit protection devices automatically trips in case of overcurrent?

Moulded Case Circuit Breaker (MCCB) (D) Signup and view all the answers

What is the purpose of earth electrodes in an earthing system?

To provide a low-resistance path to the ground (C) Signup and view all the answers

Which conductor type is most suitable for applications subject to movement or vibration?

Stranded conductors (D) Signup and view all the answers

What feature should be considered for wires that will be exposed to outdoor conditions?

UV resistance (D) Signup and view all the answers

Which configuration would a Normally Open (NO) switch have when at rest?

Contacts are open (B) Signup and view all the answers

What is the primary purpose of a distribution box in an electrical system?

To serve as a central point for distributing electrical power (A) Signup and view all the answers

Which factor is crucial when selecting a switch for handling a specific electrical load?

Current rating (B) Signup and view all the answers

What should be considered when selecting a distribution box for current demand?

The current rating in amperes (C) Signup and view all the answers

Which type of metering system is best for real-time power measurements?

Smart Meters (B) Signup and view all the answers

Which enclosure type is most suitable for industrial applications?

Metal Enclosure (D) Signup and view all the answers

What defines Time-of-Use (TOU) rates in electricity pricing?

Rates that change based on time of day (D) Signup and view all the answers

What is a primary consideration in evaluating a metering system's accuracy?

The level of precision required (A) Signup and view all the answers

What is the primary purpose of a fuse in an electrical circuit?

To protect against overcurrent conditions (B) Signup and view all the answers

Which characteristic defines a fast-blow fuse?

It quickly interrupts the circuit during short-duration over currents (D) Signup and view all the answers

What disadvantage is associated with fuses?

They need regular replacement after blowing (D) Signup and view all the answers

What does the breaking capacity of a fuse indicate?

The maximum current it can interrupt safely (C) Signup and view all the answers

What is the role of the fuse holder in an electrical system?

To secure the fuse and ensure electrical contact (A) Signup and view all the answers

What type of trip mechanism does a Miniature Circuit Breaker (MCB) use to respond to sustained over currents?

Thermal trip (C) Signup and view all the answers

Which voltage rating is NOT commonly associated with MCBs?

690V (C) Signup and view all the answers

What feature do some MCBs have that indicates the breaker has reached the end of its operational life?

End-of-Life (EOL) feature (B) Signup and view all the answers

What is the primary function of the arc chute in a Miniature Circuit Breaker (MCB)?

To extinguish electric arcs (B) Signup and view all the answers

Which statement correctly describes the breaking capacity of an MCCB?

It is the maximum fault current that the MCCB can interrupt safely (D) Signup and view all the answers

What is the primary purpose of an ELCB?

To detect and disconnect electrical circuits from leakage currents (B) Signup and view all the answers

Which type of ELCB operates by sensing an imbalance in current flowing through the live conductor?

Current-Operated ELCB (C) Signup and view all the answers

What feature of ELCBs ensures quick detection and disconnection of leakage current?

Sensitivity to leakage currents (A) Signup and view all the answers

How do inverse time characteristics influence tripping time of protective devices?

Tripping time decreases as current magnitude increases (A) Signup and view all the answers

What is indicated by the steepness of the slope on an inverse time characteristic curve?

The degree of the inverse relationship between current and tripping time (A) Signup and view all the answers

What is the main function of a contactor in an electrical system?

To switch an electrical circuit on or off (A) Signup and view all the answers

Which component of a contactor generates a magnetic field when energized?

Coil (A) Signup and view all the answers

What distinguishes an isolator from a contactor?

Isolators provide a visible break in the circuit. (C) Signup and view all the answers

Which feature is included in some isolators to enhance operational safety during maintenance?

Lockout/tagout provision (D) Signup and view all the answers

Which characteristic of contactors is essential for protecting against excessive current?

Overload protection (A) Signup and view all the answers

LT System Components

Electrical wiring components designed for lower voltage levels; includes conductors, insulation, sheath, distribution boards, switches, circuit breakers, relays, fuses, contactors, busbars, earthing components, and lighting fixtures.

Distribution Boards (DB)

Electrical panels that distribute power to various circuits or areas within a building; include MDB and Sub-DB.

Circuit Breakers (MCBs/MCCBs)

Automatic switches that trip to protect circuits from overcurrent or short circuits; MCBs are small/low current, MCCBs are for higher currents.