Electrical Cables and Components Quiz
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Questions and Answers

What is the primary purpose of the sheath in a cable?

  • To carry the electrical current.
  • To protect the cable against mechanical damage. (correct)
  • To reduce the cable's weight.
  • To provide electrical insulation between conductors.

    • The new color code for electrical cables was implemented and became compulsory before March 2011.

    False (B)

    What material is commonly used as insulation in fire-resistant cables designed to operate at temperatures up to 250°C?

    Magnesium Oxide

    Cables that are buried underground often use ______ cables to protect against mechanical damage.

    <p>armoured</p> Signup and view all the answers

    Which of the following is a characteristic of multi-core cables compared to single-core cables?

    <p>They are common for small size cables. (D)</p> Signup and view all the answers

    Match the cable component with its typical function.

    <p>Conductor = Carries electrical current Insulation = Prevents current leakage Armouring = Provides mechanical protection Sheath = Offers environmental protection</p> Signup and view all the answers

    In the cable specification 4C,120 mm2 Cu/XLPE/PVC /SWA/PVC + 70 mm2 Cu/PVC/CPC, what does 'XLPE' indicate?

    <p>The insulation material of the core conductors. (C)</p> Signup and view all the answers

    Polyester (mylar) tape is typically used as armouring for cables.

    <p>False (B)</p> Signup and view all the answers

    What is the primary reason for using single-core cables beyond 120 mm² in size?

    <p>To enhance the cable's flexibility for easier installation. (B)</p> Signup and view all the answers

    Final circuits typically carry larger currents compared to submain cables.

    <p>False (B)</p> Signup and view all the answers

    Which of the following components is a key addition to fire-resistant (FR) cables compared to standard cables?

    <p>A fire-resistant layer made of Mica or Magnesium oxide (B)</p> Signup and view all the answers

    Busducts are primarily used in low-current applications because of their large physical size compared to cables.

    <p>False (B)</p> Signup and view all the answers

    According to the guidelines, if phase conductors are 50 mm², what should be the minimum size of the CPC?

    <p>25 mm²</p> Signup and view all the answers

    What are three applications of FR cables?

    <p>Sprinkler pumps, Emergency lights, Smoke extraction fans, Fireman lift</p> Signup and view all the answers

    Cables used in final circuits typically range from ______ mm².

    <p>1.5 to 4</p> Signup and view all the answers

    The Cat CWZ fire resistance test ensures that a cable remains conductive at a temperature of 950°C for 3 hours, even under water-spray and ______ impact conditions.

    <p>mechanical</p> Signup and view all the answers

    Match the cable characteristic with its effect on current carrying capacity:

    <p>Cable Size = Decreases as size decreases Ambient Temperature = Decreases as temperature increases Installation Factor = Decreases in an enclosed environment Grouping Factor = Decreases with more cables grouped together</p> Signup and view all the answers

    Which factor does NOT directly influence the current carrying capacity of a cable?

    <p>Cable Material. (B)</p> Signup and view all the answers

    Match the characteristics with either Cables or Busducts:

    <p>Big size = Cables Low Resistance = Busducts Not Flexible = Cables Expensive = Busducts</p> Signup and view all the answers

    Using a cable with an undersized cross-sectional area will always immediately result in a short circuit and fire.

    <p>False (B)</p> Signup and view all the answers

    What is a consequence of running cables in an enclosed environment with poor ventilation?

    <p>Decreased current carrying capacity of the cables. (B)</p> Signup and view all the answers

    What is the primary concern when using cable support systems in electrical installations?

    <p>Maintaining the operability of emergency equipment during a fire. (C)</p> Signup and view all the answers

    According to the examples, a voltage drop of 4.35% in a cable is generally considered acceptable under normal operating conditions.

    <p>False (B)</p> Signup and view all the answers

    What type of cable support is typically used for managing large cables in an electrical installation?

    <p>Cable ladder</p> Signup and view all the answers

    According to CP5, all wirings installed within a wall must have adequate __________ protection.

    <p>mechanical</p> Signup and view all the answers

    What factors contribute most significantly to an increase in cable resistance?

    <p>Increase in ambient temperature (C)</p> Signup and view all the answers

    Concealed conduit is suitable for surface mounting a switched-socket outlet.

    <p>False (B)</p> Signup and view all the answers

    What is the recommended cable size for lighting circuits according to the guide?

    <p>1.5 mm² (D)</p> Signup and view all the answers

    Using an inadequately sized cable poses no risk as long as the circuit breaker is functioning correctly.

    <p>False (B)</p> Signup and view all the answers

    In the calculation of voltage drop ($V_d$), what two factors are multiplied together?

    <p>Current (I) and Resistance (R)</p> Signup and view all the answers

    Match the wiring component type with its typical installation method:

    <p>Cable Trunking = Smaller cables, final circuits Cable Conduit = Final circuits Cable Ladder = Large cables</p> Signup and view all the answers

    What is the maximum allowable voltage drop from the origin of the electrical installation to the socket outlet or fixed equipment terminals?

    <p>4%</p> Signup and view all the answers

    Cable insulation will degrade slowly over time due to ______.

    <p>overheating</p> Signup and view all the answers

    A cable with an IFL of 35A is used in a system, but its current carrying capacity (CCC) is rated for 32A. What is the most likely consequence?

    <p>Overheating of the cable (C)</p> Signup and view all the answers

    Which of the following is NOT a suggested solution for addressing voltage drop issues in an electrical installation?

    <p>Increasing the supply voltage beyond the standard range (B)</p> Signup and view all the answers

    A 3-phase system typically operates at 230V ± 10%.

    <p>False (B)</p> Signup and view all the answers

    Match the following components with their typical voltage tolerance:

    <p>Equipment = ± 10% Power Supply = ± 6% Allowable Voltage Drop = 4%</p> Signup and view all the answers

    What are the main disadvantages associated with using busducts?

    <p>High cost and custom made. (A)</p> Signup and view all the answers

    Horizontal busducts in factories are typically installed at ground level for easy access.

    <p>False (B)</p> Signup and view all the answers

    List three factors that influence the current carrying capacity of a cable.

    <p>Cable size, ambient temperature, installation factor, grouping factor</p> Signup and view all the answers

    Inadequate cable size can lead to a temperature increase, insulation __________, and potentially a fire.

    <p>degradation</p> Signup and view all the answers

    Match the cable color identification with the corresponding system (old or new):

    <p>Red, Black = Single Phase - Old Brown, Blue = Single Phase - New Red, Yellow, Blue, Black = Three Phase - Old Brown, Grey, Black, Blue = Three Phase - New</p> Signup and view all the answers

    What is the primary purpose of a fire barrier in fire retardant cables?

    <p>To provide a barrier between the conductor and insulator. (C)</p> Signup and view all the answers

    A voltage drop of 5% is generally acceptable for most equipment.

    <p>False (B)</p> Signup and view all the answers

    What conditions are specified for Conductive Water Zone (CWZ) cables?

    <p>Conductive at temperatures &gt; 950 deg C, under water spray condition, under mechanical shock impact. (A)</p> Signup and view all the answers

    Flashcards

    Oversheath

    A protective outer layer made of flame retardant PVC type ST2 or LSHF compound.

    Submain cables

    Cables designed to carry large currents, typically used in larger installations.

    Final circuits

    Cables that carry small currents, generally ranging from 1.5 to 4 mm².

    CPC cable size

    The Cross-Sectional Area of the CPC can differ from phase conductors, based on CP5 requirements.

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    Current carrying capacity

    The maximum current a cable can safely carry without overheating.

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    Ambient temperature

    The surrounding temperature which affects the current carrying capacity of cables.

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    Installation factor

    A consideration for current carrying capacity based on insulation and environment.

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    Grouping factor

    A reduction in current carrying capacity when multiple cables are installed close together.

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    Silicone Rubber

    A flexible material used in applications requiring temperature resistance from -60°C to 150°C, often in medical equipment.

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    Magnesium Oxide

    A compound used in Mineral Insulated Copper Covered (MICC) cables, known for their fire resistance and high operating temperature up to 250°C.

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    Cable Sheath

    The outer layer of a cable that protects its insulation from mechanical damage; armored cables are used in high-risk areas.

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    Single Core Cable

    A cable with one conductor set, typically used for larger sizes and single-phase applications with three cables needed (L, N, E).

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    Multi Core Cable

    A cable that contains multiple sets of conductors (3 or 4), usually for smaller size applications and three-phase systems.

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    Cable Specification X

    A description of a three-phase multi-core cable with four stranded copper conductors, insulation of XLPE, and PVC sheath; includes separate earth conductor.

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    Insulation Material

    The protective layer around conductors, often made of Cross-linked Polyethylene (XLPE), ensuring electrical safety and compatibility.

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    Armoured Cable

    A durable cable type with additional layers of aluminum or galvanized steel wires for extra protection, often used in exposed areas.

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    Cable Sizing Standards

    Recommended wire sizes for different applications; 1.5 mm² for lighting, 2.5 mm² for power sockets.

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    Inadequately Sized Cable

    A cable that is too small for its load, leading to overheating and possible failure.

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    Temperature Increase Effects

    Excess temperature from overload can break down insulation and cause shorts or fires.

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    Current Carrying Capacity (CCC)

    The maximum current a cable can carry without excessive heating.

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    Voltage Drop

    The reduction in voltage in the electrical circuit between the source and load load due to resistance.

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    Acceptable Voltage Regulation

    Must stay within specified limits: 230V ± 10% for single-phase; 400V ± 10% for three-phase systems.

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    Cable Resistance

    Resistance of a cable that affects voltage drop; measured in ohms per meter, e.g., 13mΩ/m.

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    Effects of Increased Ambient Temperature

    Higher temperature can increase cable resistance, affecting performance and safety.

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    Fire Retardant Cables

    Cables designed to resist fire damage and maintain conductivity at high temperatures.

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    Busducts

    A compact system that combines conductor, insulation, protection and support for electricity conduction.

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    Function of Busducts

    Serve to conduct electricity while integrating multiple components for efficiency and flexibility.

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    CWZ Cable

    A fire resistance test cable that remains conductive at 950°C for 3 hours, under water-spray and shock conditions.

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    Sprinkler Pump

    A pump used to supply water for sprinkler systems in case of fire.

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    Cable Tray

    Support system for organizing and protecting electrical cables.

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    Voltage Drop Formula

    The formula V=I*R calculates the voltage drop in a conductor.

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    Voltage Drop Tolerance

    The acceptable voltage drop allowed is 4% for safety.

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    Support Systems

    Structures like cable ladders or trays that hold cables in place.

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    Actual Cable Drop

    The voltage drop in a cable due to its resistance when current flows.

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    Disadvantages of Busducts

    Busducts are expensive and custom-made, limiting cost effectiveness.

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    Cable Ambient Temperature Effect

    Resistance of cable increases as ambient temperature increases, affecting performance.

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    Cable Ladder

    A support structure used for securing large cables during installation.

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    Concealed Conduit

    A pipe that protects electrical wiring, installed within walls or ceilings.

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    Mechanical Protection

    Physical safeguarding of wiring installations within walls to prevent damage.

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    CP5 Regulations

    Standards requiring safe and compliant electrical wiring installations.

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    Study Notes

    Cables and Support Systems

    • Cables are insulated conductors.
    • Cables consist of conductors, insulation, and mechanical protection.
    • Components include main, sub-mains, and final sub-circuits.
    • Cable support systems: e.g., cable ladders, cable trays, and cable conduits.
    • Fire resistance cables: designed for use in fire-prone environments, often using materials like magnesium oxide.
    • Busducts: combine conductors, insulation, mechanical protection, and support into a single unit.

    Cable Components

    • Sheath: Protects the cable from damage.
    • Conductor: Usually copper or aluminum, size determined by current rating. Stranded conductors offer flexibility.
    • Insulator: Covers the conductor, with higher insulator sizes handling higher voltages.

    Cables & Cable Components

    • Cables are insulated conductors.
    • Three main cable components are Conductor, Insulation, and Mechanical protection.

    Conductor

    • Conductor size is measured in mm².
    • Conductor material is either copper or aluminum.
    • Aluminum is lighter and cheaper, but has higher resistivity than copper, leading to a larger size for the same current carrying capacity. Copper is heavier and more expensive, but has lower resistivity.
    • Stranded conductors are twisted together for flexibility during installation.
    • Total cross-sectional area of individual wires in a stranded conductor is used to determine size.

    Conductor/Insulator

    • Stranded conductors are comprised of many small wires, enabling flexibility during installation.
    • Conductor size is the total cross-sectional area of all wires, excluding air space.
    • Insulators are the external coverings of conductors; protecting live conductors from contact.

    Other Insulations

    • Synthetic rubber insulators handle high temperatures up to 85°C.
    • Silicone rubber is used for special applications in temperatures ranging from -60°C to 150°C.
    • Magnesium oxide insulation is a fire-resistant insulator.
    • MICC cables are fire resistant, able to operate at up to 250°C.

    Color Code

    • Color coding for electrical wiring standardizes connections in single-phase and three-phase systems.
    • Old and new schemes exist.

    Single Core and Multi Core

    • Single core cables have single conductors, suitable for high-current applications.
    • Multi core cables have multiple conductors, suitable for smaller size applications.

    Cable Specification

    • Specific cables have 3-phase configurations.
    • The conductors have a cross-sectional area.
    • Insulation is cross-linked polyethylene.
    • Sheath is polyvinyl chloride.
    • Separate earth cables have a calculated size.

    Single & Multi Core Cables

    • Conductors are usually stranded copper.
    • Insulation is usually cross-linked polyethylene or other polymers.
    • Fillers, binders, bedding, armouring, and oversheaths are used as necessary for mechanical protection or specific application needs.

    Cable Specification

    • Multicore cables are common up to a 120 mm² cross-sectional area.
    • Submain cables handle high current loads.
    • Final circuits have lower current requirements.
    • Circuit protective conductors need their size calculated according to the phase conductors, typically less.

    Selection of Cable Size

    • Cable size selection is based on current carrying capacity and voltage drop.

    Current Carrying Capacity

    • Cable size directly affects the current-carrying capacity.
    • Higher ambient temperatures reduce current-carrying capacity.
    • Enclosures reduce current-carrying capacity.
    • Multiple cables together reduce current-carrying capacity.

    Selection of Cable Size

    • Selecting a cable size requires consideration of ambient temperature, installation factor, grouping factor, and design standards.
    • Small cable sizes can lead to overheating, damage, short circuits, and possible fire.
    • Large cable sizes are wasteful.
    • Standards provide minimum acceptable cable sizes for specific applications (e.g., lighting and power).

    Guide from CP5

    • Provides detailed information for calculating voltage drop.

    What happens if a cable is inadequately sized?

    • Inadequate cable sizing can cause conductor overheat.
    • This can lead to insulation breakdown, short circuits, or even fires.
    • Cable insulation degrades over time due to overheating. This should be avoided.

    Voltage Drop

    • Equipment voltage range varies with whether it's single or three phase.
    • Allowable voltage drop should be considered in calculations.
    • Drop should be less than 4% in overall wiring diagrams.

    Cable Support

    • Cable support systems include cable ladders, cable trays, and cable conduits.
    • Use appropriate supports for individual cable types. Different systems cater to various cable sizes.

    Installation Details for Socket

    • CP5 regulations mandate adequate mechanical protection for wiring within walls, including connections.
    • This is essential for safe operation within a building structure.

    Cable Support System Installation

    • Supports include metal trays or ladders, brackets, and channels.
    • These systems are used in a variety of areas including buildings.

    Fire Retardant Cables

    • Fire retardant cables are designed to continue operating during fires, which is critical.
    • Some cables have added fire resistant layers or compounds to give extra protection during a fire.

    MICC & Mica-taped FR Cables

    • Fire-resistant cables are tested under various conditions to ensure continuous safety, even in extreme situations.
    • Materials used for the cables impact the result of these tests.

    Functions of Busducts

    • Busducts combine multiple functions into one unit. (conductor, insulation, mechanical protection, support)
    • Busducts are smaller than cables for larger current requirements, and have lower resistance for high currents than cables.

    Busducts

    • Busducts combine multiple functions into a single unit.
    • Busducts, used at high currents, have low resistance. This helps reduce wiring concerns.
    • Busduct usage is common in high rise buildings and factories.

    Busducts in Factories

    • Horizontal busducts run extensively at high levels in factories.
    • Droppers are installed where power is needed.

    Cable Tray

    • Cable trays are support structures for cables.
    • Practical for many wiring needs.

    Summary 1

    • Summarizes cable components, color coding, cable drawings, current carrying capacity, and sizing criteria.

    Summary 2

    • Provides a summary of circuit voltage drops, support systems for mounting, and fire-resistant cable types.

    Summary 3

    • Busduct components, advantages (size, low resistance, ease of installation), and disadvantages (high cost, custom installation) are highlighted.

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    Test your knowledge of electrical cables! This quiz covers cable functions, color codes, insulation materials, and applications, including fire-resistant and underground cabling. Explore the differences between single-core and multi-core cables.

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