wiring methods and materials

7/21/2019 Wiring Methods and Materials

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Wiring Methods and Materials



Conductors

are substances or materials

used to convey or allow the

flow of electric current

Conductors shall be insulated



Conductors

Wireso are those electrical conductors8mm2 (AWG No. 8) and smallerin sizes.

Cableso are those larger than wires

Wires and Cables are either:

o Stranded Wire

o Solid Wire



Conductors

Stranded Wires

oconsist of a group of wires twisted toform a metallic string

o the circular mil area of a stranded

wire is found by multiplying thecircular mil area of each strand by thetotal number of the strand

conductors of size 8mm2 and larger shall

be stranded

Mil- the word mil is equal to

1/1000 of an inch was used to

describe or measure a round wire

diameter



Different Types of Cableso

Armored Cable: Type AC is a fabricated assembly of insulatedconductors enclosed in flexible metalsheath.

used ono

Both exposed and concealed work oCable trays

oDry locations

oEmbedded in plaster finish on brick or other masonry, except in damp or wetlocationso run or fished in the air voids of masonry block or tile walls where such walls are notexposed to excessive moisture or dampness.



Different Types of Cables

oFlat Conductor Cable: Type FCC consist of three or more flat copper

conductor placed edge to edge separatedand enclosed within an insulating

assembly used in

o Branch circuits

o hard smooth continuous floor surfaces




o Integrated Gas Spacer Cable: Type IGS

A factory of one or more conductors, eachindividually insulated and enclosed in a loose fit, non-

metallic flexible conduit as an integrated gas spacer cable rated through 0 to 600V.

Use ino Service entrance conductors

o Feeder or branch circuit conductor




o Metal-Clad Cable: Type MC

A factory assembly of one or moreinsulated circuit conductors with or withoutoptical fiber members enclosed in an armor ofinterlocking metal tape , or a smooth orcorrugated metallic sheath.

used for o services, feeders, and branch circuits

o power, lighting control, and signal circuits

oIndoors or outdoors

oExposed or concealed

o any raceway

o as aerial cable on a messenger

o in hazardous locations as permitted




o Medium Voltage Cable: Type MV

A single or multi-conductor solid dielectric insulatedcable rated 2001V or higher.

used ino wet or dry locations

o Raceways

o In messenger supported wiring




oMineral Insulated Cable: Type MI

Is a factory assembly of one or moreconductors insulated with a highlycompressed refractory mineral insulation

enclosed in a liquid and gas tightcontinuous copper sheath.

used ino dry, wet, or continuously moist location

o As service feeders or branch circuits




o Non-metallic Sheathed Cable: Type NM

is also a factory assembly of two ormore insulated conductors havingmoisture resistant, flame retardant,

and non-metallic material outersheath.

Used for o one or two family dwellings not exceeding 3 storey

buildings




oShielded Non-metallic Sheathed Cable: Type SNM

This type of cable is a factory assembly of two or moreinsulated conductors in an extruded core of moisture resistantand flame retardant material covered within an overlapping

spiral metal tape.

used ino hazardous locations

o Cable trays

o raceways




o Underground Feeder and Branch Circuit Cable: Type(UF)Is a moisture resistant cable used for underground connections including direct burial in

the ground as feeder or branch circuit.

o Service Entrance Cables:Type SE and USE A single or multi-conductor assembly provided with or

without an overall covering primarily used for service

wire.



Table 3.10.1.5 Minimum Size of Conductors

Conductor

Voltage Rating

(Volts)

Copper Aluminum ore

Copper- Clad

Aluminum

0-2000

2001-8000

8001-1500015001-28000

28001-35000

2.0(1.6)

8.0(3.2)

3038

50

3.5(2.0)

8.0(3.2)

3038

50

Minimum Conductor Size mm2 (mm dia.)



Insulated Conductors and Cables

oLocations

Dry and Damp Locations

FEP RHW THHW XHH

FEPB RHW-2 THHW-2 XHHW-2

MTW SA THWN Z

PFA THHN THWN-2 ZW

RHH THW-2 TW




oLocations

Wet Locations

- Moisture impervious metal-sheated

- types MTW, RHW, RHW-2, TW,THW, THW- 2, THHW, THHW-2,

THWN, THWN-2, XHHW, XHHW-2, ZW- Of a type listed for use in wet locations




oLocations

Exposed to Direct Sunlight- sunlight resistant cables

- sunlight resistant conductors

- covered with insulating materials such as tape or sleeving, that islisted, or listed or marked as being sunlight resistant.



Conductors of the same circuit

shall be contained in the same:

o raceway

oAuxiliary gutter

oCable tray

ocable bus assembly

oTrench

o

cable or cord



Marking

All conductors and Cables shall be marked to indicate thefollowing information:

oThe maximum rated voltage

oThe proper type letter or letters for the type of wire or cable

oThe manufacturers name, trademark, or other distinctivemarking by which the organization responsible for the

product can be readily identified

oThe size in millimeter square or millimeter diameter

oCable assemblies where the neutral conductor is smaller thanthe ungrounded shall be so marked.



Protection Against Corrosion andDeterioration

oRaceways

ocable trays

oCable bus

oauxiliary guttersocable armor

oBoxes

o Cabinets

o Elbows

o Couplings

o Fittingso Support

o Support hardware

o Cable sheathing

Shall be materials suitable for the environment in which they are

to be installed.




oFerrous Metal Equipment

shall be protected by a coating of listed corrosion resistant material.

EXEPTION:

stainless steel shall not be required to have protective coatings



Protection Against Corrosion and Deterioration

oProtected from Corrosion Solely by Enamel

shall not be used outdoors or in wet locations

oOrganic Coatings on Boxes or Cabinetsmarked with “Raintight,” “Rainproof,” or “OutdoorType” shall be permitted outdoors




o Non-Ferrous Metal Equipment

shall be provided with supplementary corrosion protection.

o

Nonmetallic EquipmentExposed to Sunlight

shall be listed as sunlight resistant

Chemical Exposure

shall either be inherently resistant tochemicals



Protection Against Corrosion and Deterioration

oIndoor Wet Locations

the entire wiring system, where installed exposed, includingall boxes fittings, raceways, and cable used therewith shall bemounted so that there is at least a 6 mm airspace between it and the wall or supporting surface



Raceways-------are channels or wiring accessories so

designed for holding wires, cables, or busbars that are either made of metal, plastic, or any insulating mediums.

Common Types of Racewayso Conduits

o Connectors and Other Accessories



Other Types of Raceways

oConduit coupling, elbows, and other fittings

oConduit supports, such as clamps, hanger, etc.

oCable trays, cable bus, etc.

oMetal Raceways

o Nonmetal Raceways and other



Raceways To a Different TemperaturesoSealing

shall be filled with an approved material to prevent the circulation of

warm air to a colder section of the raceway or sleeve

An explosion proof seal shall not be required for this purpose.



Raceways To a Different Temperatures

oExpansion Fittings

Raceways shall be provided with expansionfittings where necessary to compensate for thermal

expansion and contraction .



Raceway Installations

oComplete Runs

exposed raceways having hinged or removablecovers, shall be installed complete between

outlet,

Junction

Splicing points

Prior to the installation of conductors



Raceway Installations

oWelding

Metal Raceways shall not be supported,terminated, or connected by welding to

the raceway unless specifically designed to beor otherwise permitted to be in this code.



Installations of Conductors with OtherSystems

oRaceways or cable trays containing electricconductors shall not contain any pipe, tube, or equalfor steam, water, air, gas, drainage, or any other

services other than electrical.



Induced currents in Metal Enclosures or MetalRaceways

oConductors Grouped Together

--to avoid heating the surroundingmetal by induction

oIndividual Conductorsinductive effect shall be minimized by

cutting slots in the metal between the individual

holes through which the individual conductors pass

Passing all conductors in a circuit through aninsulating wall sufficiently large for all theconductors of the circuit.



Underground Installations

oMinimum Cover Requirements

shall meet the minimum cover requirementsof

table 3.0.1.5



table 3.0.1.5 Minimum Cover Requirements, 0 to 600V,Nominal, Burial in Millimeters

LEGEND

• Column 1- Direct Burial Cables or Conductors

• Column 2- Rigid Metal Conduit or Intermediate Metal Conduit

• Column 3- Nonmetallic Raceways Listed for Direct Burial w/oConcrete Encasement or other Approved Raceways

• Column 4- Residential Branch Circuits Rated 230 Volts or Lesswith GFCI Protection and Maximum Overcurrent Protectionof 20 Amperes

• Column 5- Circuits for Control of Irrigation and Landscape

Lighting Limited to not more than 30 Volts and Installed w/Type UF or in other Identified Cable or Raceway

TYPES OF WIRING METHODS OR CIRCUIT



Location of Wiring Method or

Circuit

Column 1 Column 2 Column 3 Column 4 Column 5

All Locations not

specified below600 150 450 300 150

In trench below 50mm

thick concrete or

equivalent

450 150 300 150 150

Under a building 0 (Inraceway

only)

0 0 0 (Inraceway

only)

0 (Inraceway

only)

Under minimum of 100mm thick concrete

exterior slab with no

vehicular traffic and the

slab extending not less

than 150 mm beyond the

underground installation

450 100 100 150(direct

burial)

100(In

raceway)

150




Location of Wiring Method or Circuit Column 1 Column 2 Column 3 Column 4 Column 5

Under streets, highways,

roads, alleys, driveways,

and parking lots

600 600 600 600 600

One and two family

dwelling driveway and

outdoor parking areas, and

used only for dwelling

related purposes

450 450 450 300 450

In or under airport runways,

including adjacent areas

where trespassing

prohibited

450 450 450 450 450





oListing

Cables and Insulated Conductors installed inenclosures or raceways shall be listed for use in wetlocations.

o Underground Cables Under Buildings

shall be in raceway that is extended beyond theoutside walls of the building.




o

Conductors Entering Buildingsshall be protected to the point of entrance

oService Conductors

shall have their location identified by a warningribbon that is placed in the trench at least 300mm abovethe underground installation




o Enclosure or Raceway Damage

shall be installed in rigid metal conduit,intermediate metal conduit, thick wall rigid nonmetallic conduit or equivalent

o Splices and Taps

Direct-buried conductors or cable shall be permitted to be spliced or tapped without theuse of splice boxes.




oBackfill

that contains large rocks, paving materials, cinders,large or sharply angular substances, or corrosive materialshall not be placed in an excavation where

materials may damage raceways, cables, orother substructures.




oRaceway Seals

Conduits or Raceways through which moisturemay contact live parts shall be sealed or plugged at either

or both ends.

oBushing

shall be used at the end of the conduit




o Conductors of the Same Circuit

shall be installed in the same raceway

oGround Movement

shall be arranged to prevent damage to theenclosed conductors or to the equipment connected to

the raceways.



SCOPE

USE

Installation

Construction

Specification



Article 3.32- Mineral- Insulated, MetalSheated Cable: Type MI

Mineral- Insulated, Metal Sheated Cable: Type MI

-A factory assembly of one or more conductorsinsulated with a highly compressed refractory mineralinsulation and enclosed in a liquid tight and gas tight

copper or alloy steel sheath.




Uses Permitted

services, feeders, branch circuits

power, lighting, control and signalcircuits

dry or wet location

Indoors and outdoors

exposed to oils, and gasoline In or attached to cable tray




Uses not Permitted

In underground runs

Where exposed to conditions that aredestructive and corrosive to the metallic

sheath .

Bending Radius

5 times the external diameter of metallic

sheath for cable not more than 19mm




3.32.2.1 Securing and Supporting

Staples

straps,hangers or similar fittings




3.32.3 Construction Specification

Conductors

Copper

Nickel

Nickel coated copper

Equipment Grounding

copper, shall provide an adequate path for groundingsteel, an equipment grounding conductor shall provided





Insulation

Sh all be highly compressed refractory

mineral Sheath

shall be continuous construction



Article 3.34- Non Metallic- SheathedCable: Types NM,NMC, and NMS

Non metallic- Sheathed Cable

-A factory assembly of two or moreinsulated conductors enclosed within anoverall nonmetallic jacket.

Type NM

-Insulated conductors enclosed within an

overall non metallic jacket



Article 3.34- Non Metallic- Sheathed Cable:Types NM,NMC, and NMS

3.34.1.2 Definitions

3. Type NMC

-Insulated conductors enclosed within an overall,

corrosion resistant, non metallic jacket4. Type NMS

-Insulated power or control conductors within signalingand communications conductors within an overall

nonmetallic jacket.

Article 3.34- Non Metallic- Sheathed



Article 3.34 Non Metallic SheathedCable: Types NM,NMC, and NMS

3.34.2 InstallationUses Permitted

Type NM, NMC,NMS

-dry locations

-Air voids in masonry block or tile walls

Uses Not Permitted

Types NM and NMS

-corrosive fumes Embedded masonry, concrete, adobe, fill, plaster

excessive moisture or dampness




3.34.2 InstallationAmpacity

60°C (140°F) conductor temperature rating


Construction

Outer cable sheath should be nonmetallic material

Conductors

2.0 mm square (1.6 mm dia.)-3.5 mmthrough 30 mm^2 copper conductors

or sizes





Equipment Grounding

-insulated or bare conductor

InsulationThe overall covering shall be flame retardant

and moisture resistant

A ti l 3 36



Article 3.36Power and Control Tray Cable : Type

TCPower and Control Tray Cable, typeTC

-a factory assembly of two or moreinsulated conductors,with or withoutassociated bare or covered groundingconductors, under a nonmetallic jacket.

Uses Permitted

Power ,lighting, control and signal circuits

Cable Trays, raceways, outdoor locations

industrial establishments and in wet locations



Article 3.36 Power and Control TrayCable : Type TC

3.36.2 Installation

Uses not Permitted

exposed to physical damage

installed outside a raceway or cable traysystem

exposed to direct rays of the sun, unlessidentified as sunlight resistant

Direct buried, unless identified for such use



Article 3.36 Power and Control TrayCable : Type TC

Bending Radius

Four times the overall diameter for cables 25 mm orless in diameter

3.36.3.1 Construction Specification

Construction

A metallic sheath or armor

Conductors

shall be sizes 0.75 mm^2 through 500 mm^2 copper

3.5 mm^2 through 500 mm^2 aluminum and copper-cladaluminum



Article 3.36 –Service EntranceCable:type SE and Use

3.38.1.1 Definition

Service Entrance Cable

- A single conductors or multiconductor assembly provided with orwithout an overall covering an overallcovering, primarily used for servicesand of the following types

Type SE

–Service entrance cable having a flameretardant, moisture-resistant covered



Article 3.36 –Service EntranceCable:type SE and Use

Type USE

-Service entrance cable,identified for underground use,

having a moisture resistantcovering but not required to aflame retardant covering



Article 3.36 –Service EntranceCable:Type SE and Use


Service entrance conductors

Branch circuits or feeders- Grounded Conductor Insulated

- Grounded Conductor Not Insulated

- Temperature Limitations

Construction cabled single conductor, type USE construction

recognized for underground use shall permitted to have a bare copper conductor cabled with the assembly.



Article 3.40- Underground Feeder andBranch Circuit Cable: Type UF

3.40.2 DefinitionUnderground Feeder and branch Circuit Cable,Type UF

- a factory assembly of one or more insulated conductors with

integral or an overall covering of non metallic materialsuitable for direct burial on the earth.




3.40.2 Installation

Uses Permitted

use underground

single conductor cables For wiring in wet, dry or corrosive locations

For solar photovoltaic locations

As single conductor cables

Supported by cable trays




3.40.2 Installation

Uses not Permitted

As service entrance cable

In commercial garage In theaters and similar location

In storage battery rooms

Hoistways, elevator, escalators

Hazardous locations Ampacity

60°C (140°F) conductors




3.40.3.1 Conductors 2.0 mm^2 copper

3.5 mm^2 copper clad aluminum

Sheath

flame retardant; moisture, fungus, andcorrosion resistant

Insulation

moisture-resistant types

the conductor insulation shall be rated 90°C(194°F).

Article 3.42



Intermediate Metal Conduit : Type IMC

Intermediate Metal Conduit : TypeIMC

- A steel threadable raceway of circularcross section designed for physical

protection and routing of conductors andcables and for use as an equipmentgrounding conductor when installed withits integral couplings

Article 3.42



Intermediate Metal Conduit : Type IMC

Uses Permitted

All atmospheric Conditions andOccupancies

Corrosion Environments

Cinder fill Wet locations

Dissimilar metals

Size

Minimum-IMC 15 mm

Maximum- IMC larger than raceway size100 mm shall not be used



Article 3.44- Rigid Metal Conduit:Type RMC

Rigid Metal Conduit: Type RMC- a threadable raceway of circularcross section designed for the physical protection and routing of

conductors and cables and for use asan equipment grounding conductor

-made of steel with protectivecoatings or aluminum.




3.44.2 Installation Uses Permitted

All atmospheric Condition andOccupancies

Corrosion Wet location

Size

Minimum- RMC smaller than15mm

shall not be used

Maximum- RMC smaller thanraceway size 150 mm shall not beused.




Reaming and Threading

All cut ends shall be reamed or

otherwise finished to removerough edges. Where conduit isthreaded in the field, a standardcutting die with a taper of 1 in 16(¾ in. taper per foot) shall be used.



Article 3.48- Flexible Metal Conduit :Type FMC

Flexible Metal Conduit (FMC)

-a raceway of circular cross sectionmade of helically wound, formed,

Uses Permitted

to used in exposed and concealedlocation



Article 3.48- Flexible Metal Conduit : TypeFMC

3.48.2 Installation

Uses not Permitted

In wet locations

Hoistways, storage battery roomhazardous location

Where exposed to materials havinga deteriorating effect on the

installed conductors, such as oil andgasoline

Where subject to physical damage



Article 3.50- Liquid Tight FlexibleMetal Conduit: Type FMC

A i 3 0 i i i i



Article 3.50- Liquid Tight FlexibleMetal Conduit: Type LFMC

Liquid tight flexible MetalConduit: Type LFMC

- a raceway of circular crosssection having an outer liquidtight, nonmetallic sunlightresistant jacket over an innerflexible metal core withassociated couplings, connectorsand fittings for the insullation ofelectric conductors.

A i l 3 50 Li id i h fl ibl M l



Article 3.50- Liquid tight flexible MetalConduit: Type LFMC

Uses PermittedWhere conditions of installation,

operation and maintenance requireflexibility or protection from liquids,vapors or solids

For direct burial

Uses not permitted

subject to physical damage

A ti l 3 50 Li id ti ht fl ibl



Article 3.50- Liquid tight flexibleMetal Conduit: Type LFMC

3.50.2 Installation

Size

Minimum- LFMC smaller than 15 mm electrical

raceway should not be used Maximum- the maximum size of LFMC shall be 100

mm electrical raceway size


Marking- conduit suitable for direct burial shall beso marked.

A ti l 3 52 Ri id N t lli



Article 3.52- Rigid Non metallicConduit: Type RNC

Rigid Non metallic Conduit: Type RNC

-A non metallic raceway of circular cross section,with integral or associated couplings, connectorsand fittings for the installation of electrical

conductors and cables.

A i 3 2 i i i C i



Article 3.52- Rigid Non metallic Conduit:Type RNC

3.52.2 Installation

Uses Permitted:

Concealed

Corrosive influence

Cinders

wet location

dry and damp location

exposed underground installation




Article 3.52- Rigid Non metallicconduit: Type RNC

3.52.2 InstallationUses not permitted

Hazardous locations

Support of luminaires

Physical damage

Ambient temperature

Insulation temperature Limitation

Theaters and Similar Locations





3.52.2 Installation

Size

Minimum – RNC smaller than raceway size 15 mm

shall not be used Maximum – RNC larger than raceway size 150 mm

shall not be used

Article 3 52- Rigid Non metallic conduit:



Article 3.52- Rigid Non metallic conduit:Type RNCSupports

Conduit Raceway Size (mm) Maximum Spacing Between Supports

(mm)

15-25 900

32-50 1500

65-80 1800

90-125 2100

150 2400






RNC and fittings shall be composed of suitable nonmetallic material that is resistant to moisture andchemical atmosphere

Flame retardant to impact and crushing

Each length of RNC shall be clearly and durably

mark 3000 mm

A ti l 3 53 Hi h D it P l th l



Article 3.53 – High Density PolyethyleneConduit: Type HDPE Conduit

High Density PolyethyleneConduit: Type HDPE Conduit

-A non metallic raceway ofcircular cross section, with associated

couplings, connectors, and fittings forthe installation of electrical conductors

Article 3.53 – High Density



g yPolyethylene Conduit: Type HDPEConduit

3.53.2 Installation

Uses Permitted

In discrete lengths from reels

In location subject to severecorrosive influence

In cinder fill

In direct burial installation on earthor concrete

A ti l 3 53 Hi h D it P l th l



Article 3.53 – High Density PolyethyleneConduit: Type HDPE Conduit

3.53.2 Installation

Uses not permitted

Where exposed

Within a building

In hazardous location

Where subject to ambient temperature

Article 3 53



Article 3.53High Density Polyethylene Conduit:

Type HDPE Conduit3.53.2 Installation

Size

Minimum- HDPE conduit smallerthan raceway 15 mm shall not beused

Maximum- HPDE conduit largerthan raceway size 100 mm shall not

be used.

Article 3 54 Non metallic underground



Article 3.54- Non metallic undergroundconduit conductors: Type NUCC

Non metallic underground conduitconductors: Type NUCC

-A factory assembly of conductors or cables inside anonmetallic, smooth wall conduit with a circular

cross section.

Article 3.54- Non metallic



Underground conduit conductors:Type NUCC

3.54.2 Installation

Uses Permitted:

For direct burial underground installation

Encased or embedded in concrete In cinder fill

In underground locations subject to severe corrosiveinfluence

Article 3.54- Non metallic underground



Article 3.54 Non metallic undergroundconduit conductors: Type NUCC

3.54.2 Installation

Uses Not permitted:

In exposed location

Inside Buildings Bends

-shall be manually made so that the conduit will notdamage

Article 3 54 Non metallic underground



Article 3.54- Non metallic undergroundconduit conductors: Type NUCC


1. General- NUCC is an assembly that is provided in

continuous length, shipped in a coil, reel or carton

Article 3 56 Liquid tight flexible Non



Article 3.56- Liquid tight flexible Nonmetallic conduit: Type LFNC

Liquid tight flexible Nonmetallic conduit: Type LFNC

-a smooth seamless inner core andcover bonded together and having one

or more reinforcement layers.

-a smooth inner surface with integralreinforcement within the

conduit wall, designated as Type

LFNC-B




Article 3.56-Liquid tight flexible Nonmetallic conduit: Type LFNC

Uses permitted Where flexibility is required for

installation, operation andmaintenance

Where protection of the containedconductors is required from vapors,liquids, solids

For outdoor location





Uses not permitted: Where subject to physical damage

Where the operating voltage of thecontained conductors is in excess of

600 volts.

Size

Minimum: LFNC smaller than

raceway size 15 shall not be usedMaximum: larger than raceway size

100 mm shall not be used





BendsBends in conduit shall be so made that the conduit is not

damae and internal diameter of the conduit is not effectivelyreduced


Construction

shall be provided in continuous length capable of beingshipped in a coil, reel, or carton without damage.

Marking

-shall be marked at least every 600 mm

Article 3 58



Article 3.58Electrical Metallic Tubing:Type EMT

Electrical Metallic Tubing (EMT)

- An unthreaded thin wall raceway ofcircular cross section designed for he physical protection and routing ofconductors and cables and for use asan equipment grounding conductorswhen installed utilizing appropriate

fittings.

Article 3 58





Exposed and concealed

Corrosion Protection

Wet Locatiions

Uses Not Permitted

Where during installation or afterward/ it

will subject to dammage Where protected from corrosion solely by

enamel

Article 3 58




Size Minimum-EMT smaller than raceway size

15mm shall not be used

Maximum-shall be raceway size 100mm


Construction

factory threaded integral couplings shall be permitted, theads should be factory made

Marking

-EMT shall be clearly and durably marked at leastevery 3000mm

Article 3 60



Article 3.60Flexible Metallic Tubing: Type FMT

• Flexible Metallic Tubing (FMT)- A raceway that is circular in cross section,

flexible, metallic and liquid tight without anonmetallic jacket.

Uses Permitted In dry location

Where concealed

In accessible location

For system voltage of 1000 voltsmaximum

Article 3 60



Article 3.60Flexible Metallic Tubing: Type FMT

Uses not permitted In hoistways

Storage battery rooms

Hazardous location

Underground for direct earth burialWhere subject to physical damage

In lengths over 1800 mm

Size

Minimum-smaller than raceway size 15 mmshall not be used

Maximum-shall be raceway size 20mm

Article 3 62



Article 3.62Electrical Non metallic Tubing:Type ENT

Electrical Non metallic Tubing: TypeENT

-a non metallic or associated couplings,connectors, annd fittings for theinstallation of electric conductors.

Uses Permitted

In any building not exceeding above gradeas follows

For exposed work

Concealed within walls,floors, ceilings.

Article 3 62




Uses permitted In location subject to corrosive influence and where subject

to chemicals.

In concealed dry and damp locations

Above suspended ceilingsUses not permitted

Hazardous locations

For the support of luminaires and other equipment

Where subject to ambient temperature

For direct earth burial

Article 3 62




Uses not permitted

Where the voltage is over 600 volts

In theaters

Exposed to the direct rays of the sun Size

Minimum

-ENT smaller than raceway size 15 mm shall not be used

Maximum

-ENT larger than raceway size 50mm shall not be used.

Article 3 62





Construction

-ENT shall be made of material that does not exceed theignitibility, flammability, smoke generation, and toxicitycharacteristic of rigid polyvinyl chloride

Markings

-shall be clearly and durably marked at least every 3000 mm.

-The type of material shall also be included in the marking

-type, printed, quantity are identified by printed tag



Article 3.66-Auxiliary Gutters

3.66.1.2 DefinitionMetallic Auxiliary Gutters

-Sheet metal enclosure with hinged orremovable covers for housing and protectingelectric wires, cable, and bus bars in which

conductors are laid in place after the wireways has been installed as a complete system.

Non Metallic Auxiliary Gutters

-flame retardant, nonmetallic enclosure withremovable covers for housing and protectingelectric wires, cables, and bus bars in whichconductors are laid in place after the wire wayhas been installed as a complete system.

A i l 3 66 A ili G




A i l 3 66 A ili G




3.66.2 Installation

Uses Permitted

Sheet Metal Auxiliary Gutters

Non metallic Auxiliary Gutters Uses not Permitted

To enclose switches over current devices, appliances orother similar equipment.

To extend a greater distance than 9000mm beyond theequipment that it suplements.

A ti l 3 66 A ili G tt





Construction

Electrical and mechanical Continuity

Substantial Construction Smooth rounded edges

Covers

Clearance of Bare live parts

A ti l 3 66 A ili G tt




Markings

Outdoors

-Suitable for exposure to sunlight

-Suitable for use in wet locations-Installed conductor insulation temperature rating

Indoors

Installed conductor insulation temperature rating

A ti l 3 68 B



Article 3.68 -Busways

3.6.1.2 Definition

• Busway

- a grounded metal enclosure containing factory mounted bareor insulated conductors, which are usually copper, aluminum,

bars, rods, or tubes.

3.68.2 Installation

• Uses permitted

1. Exposed

2. Concealed

3. Through walls and floors

A ti l 3 68 B




• Uses not Permitted

1. Physical damage

2. Hoistways

3. Hazardous locations4. Wet locations

5. Working platform

A ti l 3 68 B




3.68.3 ConstructionMarkings

-shall be marked with thevoltage and current rating and

with manufacturer’s name /trademark visible afterinstallation

A ti l 3 70 C bl B



Article 3.70-Cable Bus

Cable Bus-an assembly of insulated conductorswith fittings and condutor terminationsin a completely enclosd, ventilated

protective metal housing.Use

- permitted at any voltage or current forwhich spaced conductors are rated and

shall installed only for exposed work

A ti l 3 70 C bl B



Article 3.70-Cable Bus

Types of Conductors

insulation rating of 75°C (167°F) or higher

Size and Number of Conductors

The size and number of conductors shall be that forwhich the cablebus is designed, and in no case smaller

than 50 mm^2

ARTICLE 3.72CELLULAR CONCRETE



CELLULAR CONCRETEFLOOR RACEWAYS

3.72.1.2 Definitions

Cell

- A single, enclosed tubular space in a floor made of

precast cellular concrete slabs, the direction of the cell being parallel to the direction of the floor member.

Header

- Transverse metal raceways for electric conductors,

providing access to predetermined cells of a precastcellular concrete floor.

ARTICLE 3.72CELLULAR CONCRETE



CELLULAR CONCRETEFLOOR RACEWAYS

Uses Not Permitted

Where subject to corrosive vapor

In any hazardous (classified) 5.1.2.1(b)(3)

In commercial garages, othe r than for supplyingceiling outlets or extensions to the area below the floor

but not above

ARTICLE 3.74 — CELLULARMETAL



METALFLOOR RACEWAYSCellular Metal Floor Raceway-The hollow spaces of cellularmetal floors, together with suitable fittings,that may be approved as enclosures for

electric conductors.Cell- A single enclosed tubular space in a cellularmetal floor

member, the axis of the cell being parallel tothe axis of the metal floor member.

ARTICLE 3.74 — CELLULARMETAL



METALFLOOR RACEWAYS

Header

-A transverse raceway for electric conductors, providing access to predetermined cells of a

cellular metal floor.Uses Not Permitted

Where subject to corrosive vapor

In any hazardous (classified) location exc

ARTICLE 3.76 — METAL WIREWAYS



3.76.1.2 Definition

Metal Wireways

- Sheet metal troughs with hinged or removable coversfor housing and protecting electric wires and cable andin which conductors are laid in place af ter the wirewayhas been installed as a complete system.

ARTICLE 3.78 — NONMETALLICWIREWAYS



WIREWAYS

3.78.1.2 Definition

Nonmetallic Wireways

-Flame retardant, nonmetallic troughswith removable covers for housing and protecting electric wires and cables inwhich conductors are laid in placeafter the wireway has been installed as

a complete system.

ARTICLE 3.82 — NONMETALLIC



EXTENSIONS

Nonmetallic Extension.

-An assembly of two insulated conductors

within a (anonmetallic jacket or an

extruded thermoplastic covering. Uses Permitted.

From an Existing Outlet

Exposed and in a Dry Location. Residential or Offices

ARTICLE 3.82 — NONMETALLIC



EXTENSIONS

Uses Not Permitted

In unfinished basements, attics, or roof spaces

Where the voltage between conductors exceeds 150

volts for nonmetallic surface extension and 300 volts foraerial cable

Where subject to corrosive vapors

Where run through a floor or partition, or outside the

room in which it originates

ARTICLE 3.84 — STRUT-TYPE



CHANNEL RACEWAY

Strut-Type Channel Raceway-A metallic raceway that is intended to be mounted to the surface of orsuspended from a structure, with

associated accessories for theinstallation of electrical conductorsand cables.

ARTICLE 3.86 — SURFACE METAL



RACEWAYS

3.86.1.2 Definition

Surface Metal Raceway

-A metallic raceway that is intended to be mounted to the surface of a

structure, with associated couplings,connectors, boxes, and fittings for theinstallation of electrical conductors.

ARTICLE 3.88 — SURFACE



NONMETALLIC RACEWAYS

Surface Nonmetallic Raceway-A nonmetallic raceway that isintended to be mounted to thesurf ace of a structure, with

associated couplings,connectors, boxes, and fittingsfor the installation of electricalconductors.

ARTICLE 3.90 — UNDERFLOOR



RACEWAYS

Use Permitted

be permitted beneath the surface ofconcrete or other flooring material or

in office occupancies where laid flush with the concrete floor andcovered with linoleum or equivalentfloor covering.

ARTICLE 3 92 — CABLE TRAYS



ARTICLE 3.92 — CABLE TRAYS

Cable Tray System-A unit or assembly of units or

sections and associated fittingsforming a structural system used

to securely fasten or supportcables and raceways.

ARTICLE 3.94 — CONCEALED KNOB-



AND-TUBE WIRING

3.94.1.2. DefinitionConcealed Knob-and-TubeWiring

-A wiring method usingknobs, tubes, and flexiblenonmetallic tubing for the protection and support ofsingle insulated conductors.

ARTICLE 3.94 — CONCEALED KNOB-



AND-TUBE WIRING


For extensions of existinginstallations

Elsewhere by special permission

Uses Not Permitted.

Commercial garages

Theaters and similar locations

Motion picture studios

Hazardous (classified) locations

ARTICLE 3.96 — MESSENGER



SUPPORTED WIRINGMessenger Supported Wiring

-An exposed wiring support systemusing a messenger wire to supportinsulated conductors by any one of thefollowing:

A messenger with rings and saddlesfor conductor support

A messenger with a field-installedlashing material for conductor support

Factory-assembled aerial cable

ARTICLE 398 — OPEN WIRING ON



INSULATORS

3.98.1.2 Definition.Open Wiring onInsulators

-An exposed wiring method

using cleats, knobs, tubes,and flexible tubing for the protection and support ofsingle insulated conductors

run in or on buildings.

HV

D

• It is related to the tap changer control system.

• It occurs on both rectifier and the inverter side of the transmission.

• (TC cont) Designed to control the Load tap changers of the converter transformers.



D

C• Objective is to keep the

ordered alpha α

gamma γ

DC voltage

- at the preset values determined by the Voltage and Angle Reference Calculation(VARC).

• Operate much slower than the basic control function, acting on control angle alpha

α

• One tap changer step takes some seconds to execute.

• Thus there is no risk for interference between the basic converter control functionand the tap changer control systems.

• One step gives a change of 1-1.5% of rated value in the valve side voltage.

(TC @ Rec Sta) PURPOSE: to maintain the delay angle alpha in a certain range• If the alpha reduces below the predefined value, it starts to increase the voltage by

varying the number of turns in the primary side to keep the alpha in certain rangefor fast controlling current

• If alpha increased above a certain predefined maximum value then the tap changerwould decrease the voltage to keep the alpha within the limit.

• The voltage in the rectifier end of the line can be controlled by adding a proportionalamount of the line voltage drop, Rd *Id to the measured inverter end voltage.

• Normally used to keep the firing angle α as close as possible to the rated value whichnormally chosen to 15 degrees.



normally chosen to 15 degrees.

• The control characteristics must include a dead band also here and ± step of 1.25%from rated value corresponds to a region from 12° to

17.5° in α.• Udio *cos a in the expression constant, at varying rectifier AC voltage,

the current control system responds to it by changing α.

• The (TCC) system in the rectifier compares an a response signal to

a reference value and at a significant deviation it orders the tap changer to step and

change Udio.• (TC @ Inv Sta) Tap changer control maintains the DC voltage equal to reference voltage.

• Normally, gamma is kept as constant for proper commutation.

• Any increase or decrease in the DC voltage will be controlled by tap changer

• Since tap changers would take more time to control the converter voltage than currentor voltage controller, dynamic interaction between both controllers can be avoided.

• The tap changers in the inverter in the extinction angle γ control are normally used tocontrol the voltage on the DC line.

• The voltage response measured by a voltage divider is compared to an order, Udi0.

• For a significant difference between the two signals, the tap changer control system(TCC) orders increase or decrease of the valve side voltage.

• Because of the stepwise character of the tap changer, the controlsystem must be provided with dead band. To bring the voltageback to the reference value and thus avoid hunting, the dead bandshould have a width of at least one tap changer step

• When the inverter takes over the current control the DC voltage

than characteristic harmonics

• These are due to:

1. Inbalance in the operation s)of two bridges

firing a 12 pulse converter (residual harmonics)



• When the inverter takes over the current control, the DC voltagetap changer control must be locked

Harmonics

• Harmonics are electric voltages and currents that appear on theelectric power system as a result of non-linear electric loads.

• Harmonic instability may occur in high-voltage dc (HVDC) linksdue to dynamic interactions between HVDC terminals and theimpedance of the dc lines or cables.

• The harmonics that come from the HVDC will not only increaseloss, thermal stress of equipment, reduce equipment life,

interference with communications, metering, protection andcontrol devices to work properly and in some cases, it can evenlead to the collapse of the system.

• Two types of harmonics in electrical power systems

1. current harmonics

2. voltage harmonics

• Generation of Harmonics

1. harmonics-characteristic

2. non-characteristic

• Characteristic Harmonics - harmonics of those order which arealways present even under ideal operation-

•Non Characteristic Harmonics- the harmonics of the order other

firing a 12 pulse converter (residual harmonics)

2. firing angle errors

3. unbalance and distortion of AC Voltages

4.unequal transformer leakage impedances

• The presence of harmonics leads to low system efficiency, poor

power factor, increased loss and reactive power componentsfrom AC and also on the equipment present in the system andinterference on the telecommunication lines.

• for reduction of harmonics, filters are used. Here we use ahybrid configuration of both passive and active filters for improved power handling capacity of semiconductor devicesand better performance.

(generation of

triplen and ev

harmonics and

their analysis icomplex)

• The above circuit diagram consists of a three- phase generator source of 345Kv at frequency of 50Hz which is connected to theconverter transformer for stepping down voltage to 211KV for transmission over long distance. Further a 12-pulse thyristor bridge converter is connected, which is called as rectifier for

i AC DC hil h h h d i

shunt and series. But these filters also have hybrid configurationof passive filters to improve the power handling capacity ofsemiconductor devices.

harmonic analysis in a basic HVDC transmission system and theimportance of using filters for the reduction of the harmonic



converting AC to DC while the converter at the other end isreferred as inverter for vice-versa conversion. The rectifier-endhas firing angle (α) control for ignition of the thyristor while theinverter-end contains the extinction/gamma control (δ).

• A. Three Phase Converter - The converter transformers areconstructed by three phase three winding on same corematerial by connecting primary and secondary windings aseither wyes or deltas.

• B. Pulse Generator - a discrete twelve pulse generator is used tofire the thyristors of HVDC rectifier built with two six pulsebridges. The four inputs of a pulse generator are alpha firingangle (in degrees), other three inputs are phase to groundsynchronizing voltages. There are two outputs of a pulsegenerator, one connected to wye secondary winding oftransformer and other connected to delta winding of secondarytransformer. Similarly for gamma angle control at the inverter-side, a twelve-pulse firing control and discrete gammameasurement subsystem is used for the two extinction/gammaangle triggering for the inverter.

• C. Filters - Both the ends have AC filters for reducing theharmonic distortion in the AC-side of the system and DC filtersor smoothening reactors on the DC line for red cing the ripple

importance of using filters for the reduction of the harmonicdistortions in the system to improve the efficiency and reducevarious ill effects due to the harmonics.

On observing the various waveforms with and without the

insertion of filters, we may conclude that on connecting theharmonic filters the voltage values is increased and optimizedwhile the high current values are reduced.

wiring methods and materials

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