Questions and Answers
What is the minimum vertical clearance required for primary lines when crossing a highway?
Where should poles be located in relation to the road right-of-way or property line?
What is a requirement for the location of poles and transformer supports along public roads?
Which of the following is NOT a consideration for the installation of overhead transmission lines?
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What is the minimum vertical clearance for primary lines along the side of a highly urbanized area?
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What happens to the heat generated in a conductor placed in an enclosed conduit compared to when it is in free air?
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Which type of cable is known for its highly compressed refractory mineral insulation?
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What characterizes Non-Metallic Sheathed Cable (Type NM or NMC)?
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Which type of cable is specifically designed for field installation in square structural channels?
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What is the function of the moisture-resistant cable known as Type UF?
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What distinguishes Flat Conductor Cable (Type FCC)?
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What type of cable encapsulates insulated conductors in an extruded core of moisture resistant and flame retardant material?
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Which type of cable is best characterized as having a continuous copper sheath?
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What is one advantage of flexible metal conduit wiring over rigid metal conduits?
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What material covers armored cable wiring to provide protection?
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What type of wiring consists of a factory-assembled channel with conductors for two to four circuits?
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In surface metal raceway wiring, how are the wires supported?
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What is the maximum length for flexible metal conduit wiring?
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What types of cables must be used when a cable tray/open raceway is functioning as a general wiring system?
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Which type of raceway is recognized by NEC as having underfloor ducts?
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What is a characteristic of ceiling raceway systems?
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What is the minimum vertical clearance requirement for secondary, neutral, and service lines when crossing the highway?
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What is the minimum distance that a pole must maintain from a fire hydrant?
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What is the minimum vertical clearance from the crown of the road pavement for poles when installed along the highway?
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When overhead lines are arranged for buildings exceeding 15 m in height, what is the minimum required clear space for ladder access?
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What minimum distance must be maintained from the curb for poles?
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In a highly urbanized area, what minimum clearance must be observed when installing lines along the street?
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What requirement exists for power lines attached to buildings?
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What should be avoided when positioning poles and towers near street corners?
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What is the minimum thickness required for walls of vaults constructed from reinforced concrete?
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Which type of material is acceptable for constructing the ducts for ventilation?
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What is the minimum requirement for a door sill or curb within the vault?
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How thick should the coating on the inside wall surface of hollow concrete block vaults be?
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What should be ensured regarding the location of ventilation openings?
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Which of the following is an essential feature of entrance doors for vaults?
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What is the minimum fire resistance required for construction materials used in vaults?
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How is ventilation of vaults typically achieved?
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Study Notes
Electrical Conductor Types and Heat Dissipation
- Heat generated in conductors is influenced by current flow and conductor resistance; enclosed conduits limit heat dissipation compared to open air.
Mineral Insulated Cable (Type MI)
- Factory-assembled cable with conductors insulated using highly compressed refractory minerals within a liquid and gas-tight copper sheath.
Non-Metallic Sheathed Cable (Type NM or NMC)
- Known as ROMEX, this cable features two or more insulated conductors housed in moisture-resistant, flame-retardant non-metallic material.
Shielded Non-Metallic Sheathed Cable (Type SNM)
- Comprises insulated conductors encased in an extruded core of moisture-resistant, flame-retardant material.
Underground Feeder and Branch Circuit Cable (Type UF)
- Moisture-resistant cable designed for underground use, allowing for direct burial as a feeder or branch circuit.
Flat Cable Assemblies (Type FC)
- Consist of parallel conductors integrated with insulating material for efficient field installation in square structural channels.
Flexible Metal Conduit Wiring
- Easier installation compared to rigid metal conduits, available in lengths from 25 ft to 250 ft, accommodating various cable sizes.
Armored Cable Wiring (BX)
- Contains rubber or thermoplastic covered wires with layers of flexible steel armor for protection against moisture and physical damage.
Surface Metal Raceway Wiring
- Thin sheet steel casings support exposed wires, must be continuous between outlets and junctions, used for general wiring.
Cable Tray/Open Raceway
- Provides continuous support for approved cables, required to be self-protected and jacketed types when used in general wiring systems.
Floor Raceways
- NEC recognizes three types:
- Underfloor Ducts (UF) installed beneath flooring systems.
- Designed for strategic placement to accommodate cabling needs.
Power Line Clearance Regulations
- Primary lines require a vertical clearance of 10 m from road pavements.
- Secondary lines must maintain a clearance of at least 7.5 m.
Pole and Structure Placement
- Poles should not obstruct pedestrian paths or drainage.
- Transformers and power lines need approved attachment plans and must allow sufficient clearance for maintenance.
Vault Construction Requirements
- Walls and roofs must be robust, using reinforced concrete or masonry, with specific thickness guidelines.
- Adequate fire resistance and ventilation to manage transformer heat levels are critically enforced.
Ventilation Standards
- Ventilation openings must be placed away from combustible materials, ensuring effective air circulation to control temperature within transformer vaults.
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Description
This quiz covers various types of electrical conductors, including their construction and thermal characteristics. You'll learn about Mineral Insulated Cable, Non-Metallic Sheathed Cable, and more, focusing on their applications and properties. Test your knowledge on how these conductors manage heat dissipation and their practical uses.
