Wiring Methods and Materials
Conductors
are substances or materials
used to convey or allow the
flow of electric current
Conductors shall be insulated
Conductors
 Wires
o are those electrical conductors
8mm2 (AWG No. 8) and smaller
in sizes.
 Cables
o 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 to
form a metallic
string
o the circular mil area of a stranded
wire is found by multiplying the
circular mil area of each strand by the
total number of the strand
Mil- the word mil is equal to
1/1000 of an inch was used to
describe or measure a round wire
diameter
conductors of size 8mm2 and larger shall
be stranded
Different Types of Cables
o Armored Cable: Type AC
 is a fabricated assembly of insulated
conductors enclosed in flexible metal
sheath.
 used on
oBoth exposed and concealed work
oCable trays
oDry locations
oEmbedded in plaster finish on brick or
other masonry, except in damp or wet
locations
o run or fished in the air voids of masonry
block or tile walls where such walls are not
exposed 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 separated
and enclosed within an insulating
assembly
 used in
o Branch circuits
o hard smooth continuous floor surfaces
Different Types of Cables
o Integrated Gas Spacer Cable: Type IGS
 A factory of one or more conductors, each
individually insulated and enclosed in a loose fit, nonmetallic flexible conduit as an integrated gas spacer
cable rated through 0 to 600V.
 Use in
o Service entrance conductors
o Feeder or branch circuit conductor
Different Types of Cables
o Metal-Clad
Cable: Type MC
 A factory assembly of one or more
insulated circuit conductors with or without
optical fiber members enclosed in an armor of
interlocking metal tape , or a smooth or
corrugated 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
Different Types of Cables
o Medium Voltage Cable: Type MV
 A single or multi-conductor solid dielectric insulated
cable rated 2001V or higher.
 used in
o wet or dry locations
o Raceways
o In messenger supported wiring
Different Types of Cables
oMineral Insulated Cable: Type MI
 Is a factory assembly of one or more
conductors insulated with a highly
compressed refractory mineral insulation
enclosed in a liquid and gas tight
continuous copper sheath.
 used in
o dry, wet, or continuously moist location
o As service feeders or branch circuits
Different Types of Cables
oNon-metallic Sheathed Cable: Type NM
 is also a factory assembly of two or
more insulated conductors having
moisture resistant, flame retardant,
and non-metallic material outer
sheath.
Used for
o one or two family dwellings not exceeding 3 storey
buildings
Different Types of Cables
oShielded Non-metallic Sheathed Cable: Type SNM
 This type of cable is a factory assembly of two or more
insulated conductors in an extruded core of moisture resistant
and flame retardant material covered within an overlapping
spiral metal tape.
 used in
o hazardous locations
o Cable trays
o raceways
Different Types of Cables
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
Minimum Conductor Size mm2 (mm dia.)
Conductor
Voltage Rating
(Volts)
0-2000
2001-8000
8001-15000
15001-28000
28001-35000
Copper
2.0(1.6)
8.0(3.2)
30
38
50
Aluminum ore
Copper- Clad
Aluminum
3.5(2.0)
8.0(3.2)
30
38
50
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
Insulated Conductors and Cables
oLocations
 Wet Locations
- Moisture impervious metal-sheated
- types MTW, RHW, RHW-2, TW,THW, THW2, THHW, THHW-2,
THWN, THWN-2,
XHHW, XHHW-2, ZW
- Of a type listed for use in wet locations
Insulated Conductors and Cables
oLocations
 Exposed to Direct Sunlight
- sunlight resistant cables
- sunlight resistant conductors
- covered with insulating materials such as tape
or sleeving, that is
listed, 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 the
following information:
oThe maximum rated voltage
oThe proper type letter or letters for the type of wire or cable
oThe manufacturers name, trademark, or other distinctive
marking 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 than
the ungrounded shall be so marked.
Protection Against Corrosion and
Deterioration
oRaceways
ocable trays
oCable bus
oauxiliary gutters
ocable armor
oBoxes
o
o
o
o
o
o
o
Cabinets
Elbows
Couplings
Fittings
Support
Support hardware
Cable sheathing
Shall be materials suitable for the environment in which they are
to be installed.
Protection Against Corrosion and
Deterioration
oFerrous Metal Equipment
shall be protected by a coating of
corrosion resistant material.
listed
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 Cabinets
marked with “Raintight,” “Rainproof,”
Type” shall be permitted outdoors
or “Outdoor
Protection Against Corrosion and
Deterioration
o Non-Ferrous Metal Equipment
shall be provided with supplementary
protection.
o Nonmetallic Equipment
 Exposed to Sunlight
shall be listed as sunlight resistant
Chemical Exposure
shall either be inherently resistant to
chemicals
corrosion
Protection Against Corrosion and Deterioration
oIndoor Wet Locations
the entire wiring system, where installed exposed, including
all boxes fittings, raceways, and cable used therewith shall be
mounted 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 Raceways
o 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
oNonmetal Raceways and other
Raceways To a Different Temperatures
oSealing


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 expansion
fittings where necessary to compensate for thermal
expansion and contraction .
Raceway Installations
oComplete Runs
exposed raceways having hinged or removable
covers, 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 be
or otherwise permitted to be in this code.
Installations of Conductors with Other
Systems
oRaceways
or cable trays containing electric
conductors shall not contain any pipe, tube, or equal
for steam, water, air, gas, drainage, or any other
services other than electrical.
Induced currents in Metal Enclosures or Metal
Raceways
oConductors Grouped Together
--to avoid heating the surrounding
metal by induction
oIndividual Conductors
inductive 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 an
insulating wall sufficiently large for all the
conductors of the circuit.
Underground Installations
oMinimum Cover Requirements
shall meet the minimum cover
of
table 3.0.1.5
requirements
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/o
Concrete Encasement or other Approved Raceways
• Column 4- Residential Branch Circuits Rated 230 Volts or Less
with GFCI Protection and Maximum Overcurrent Protection
of 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 below
600
150
450
300
150
In trench below 50mm
thick concrete or
equivalent
450
150
300
150
150
Under a building
0 (In
0
0
0 (In
0 (In
raceway
only)
raceway
only)
150
150
raceway
only)
Under minimum of 100
mm thick concrete
exterior slab with no
vehicular traffic and the
slab extending not less
than 150 mm beyond the
underground installation
450
100
100
(direct
burial)
100
(In
raceway)
TYPES OF WIRING METHODS OR CIRCUIT
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
Underground Installations
oListing
Cables and Insulated Conductors installed in
enclosures or raceways shall be listed for use in wet
locations.
o Underground Cables
Under Buildings
shall be in raceway that is extended
outside walls of the building.
beyond the
Underground Installations
oConductors Entering Buildings
shall be protected to the point of entrance
oService Conductors
shall have their location identified by a warning
ribbon that is placed in the trench at least 300mm above
the underground
installation
Underground Installations
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
the
use of splice boxes.
Underground Installations
oBackfill
that contains large rocks, paving materials, cinders,
large or sharply angular substances, or corrosive material
shall not be placed in an
excavation
where
materials may damage raceways,
cables,
or
other substructures.
Underground Installations
oRaceway Seals
Conduits or Raceways through which
moisture
may contact live parts shall be sealed or plugged at either
or both ends.
oBushing
shall be used at the end of the conduit
Underground Installations
o Conductors of the Same Circuit
shall be installed in the same raceway
oGround Movement
shall be arranged to prevent damage to the
enclosed conductors or to the equipment connected to
the raceways.
SCOPE
Construction
Specification
USE
Installation
Article 3.32- Mineral- Insulated, Metal
Sheated Cable: Type MI
Mineral- Insulated, Metal Sheated Cable: Type MI
-A factory assembly of one or more conductors
insulated with a highly compressed refractory mineral
insulation and enclosed in a liquid tight and gas tight
copper or alloy steel sheath.
Article 3.32- Mineral- Insulated, Metal
Sheated Cable: Type MI
Uses Permitted
 services, feeders, branch circuits
 power, lighting, control and signal
circuits
 dry or wet location
 Indoors and outdoors
 exposed to oils, and gasoline
 In or attached to cable tray
Article 3.32- Mineral- Insulated, Metal
Sheated Cable: Type MI
Uses not Permitted
In underground runs
 Where exposed to conditions that are
destructive and corrosive to the metallic
sheath .
 Bending Radius
 5 times the external diameter of metallic
sheath for cable not more than 19mm
Article 3.32- Mineral- Insulated, Metal
Sheated Cable: Type MI
3.32.2.1 Securing and Supporting
Staples
straps,
hangers or similar fittings
Article 3.32- Mineral- Insulated, Metal
Sheated Cable: Type MI
3.32.3 Construction Specification
Conductors
 Copper
 Nickel
Nickel coated copper
Equipment Grounding
copper, shall provide an adequate path for grounding
steel, an equipment grounding conductor shall provided
Article 3.32- Mineral- Insulated, Metal
Sheated Cable: Type MI
3.32.3 Construction Specification
Insulation
Sh all be highly compressed refractory
mineral
 Sheath
shall be continuous construction
Article 3.34- Non Metallic- Sheathed
Cable: Types NM,NMC, and NMS
Non metallic- Sheathed Cable
-A factory assembly of two or more
insulated conductors enclosed within an
overall 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 jacket
4. Type NMS
-Insulated power or control conductors within signaling
and communications conductors within an overall
nonmetallic jacket.
Article 3.34- Non Metallic- Sheathed
Cable: Types NM,NMC, and NMS
3.34.2 Installation
Uses 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
Article 3.34- Non Metallic- Sheathed
Cable: Types NM,NMC, and NMS
3.34.2 Installation
Ampacity
60°C (140°F) conductor temperature rating
3.34.3 Construction Specification
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
Article 3.34- Non Metallic- Sheathed
Cable: Types NM,NMC, and NMS
3.34.3 Construction Specification
 Equipment Grounding
-insulated or bare conductor
 Insulation
The overall covering shall be flame retardant
and moisture resistant
Article 3.36
Power and Control Tray Cable : Type
TC
Power and Control Tray Cable, type
TC
-a factory assembly of two or more
insulated conductors,with or without
associated bare or covered grounding
conductors, 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 Tray
Cable : Type TC
3.36.2 Installation
Uses not Permitted
 exposed to physical damage
 installed outside a raceway or cable tray
system
 exposed to direct rays of the sun, unless
identified as sunlight resistant
 Direct buried, unless identified for such use
Article 3.36 Power and Control Tray
Cable : Type TC
Bending Radius

Four times the overall diameter for cables 25 mm or
less 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-clad
aluminum
Article 3.36 –Service Entrance
Cable:type SE and Use
3.38.1.1 Definition
Service Entrance Cable
- A single conductors or multi
conductor assembly provided with or
without an overall covering an overall
covering, primarily used for services
and of the following types
Type SE
–Service entrance cable having a flame
retardant, moisture-resistant covered
Article 3.36 –Service Entrance
Cable:type SE and Use
Type USE
-Service entrance cable,
identified for underground use,
having a moisture resistant
covering but not required to a
flame retardant covering
Article 3.36 –Service Entrance
Cable:Type SE and Use
3.36.2 Installation
Uses Permitted
 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 and
Branch Circuit Cable: Type UF
3.40.2 Definition
Underground 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 material
suitable for direct burial on the earth.
Article 3.40- Underground Feeder and
Branch Circuit Cable: Type UF
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
Article 3.40- Underground Feeder and
Branch Circuit Cable: Type UF
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
Article 3.40- Underground Feeder and
Branch Circuit Cable: Type UF
3.40.3.1 Conductors
 2.0 mm^2 copper
 3.5 mm^2 copper clad aluminum
 Sheath
 flame retardant; moisture, fungus, and
corrosion 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 : Type
IMC
- A steel threadable raceway of circular
cross section designed for physical
protection and routing of conductors and
cables and for use as an equipment
grounding conductor when installed with
its integral couplings
Article 3.42
Intermediate Metal Conduit : Type IMC
Uses Permitted
 All atmospheric Conditions and
Occupancies
 Corrosion Environments
 Cinder fill
 Wet locations
 Dissimilar metals
 Size
 Minimum-IMC 15 mm
 Maximum- IMC larger than raceway size
100 mm shall not be used
Article 3.44- Rigid Metal Conduit:
Type RMC
Rigid Metal Conduit: Type RMC
- a threadable raceway of circular
cross section designed for the
physical protection and routing of
conductors and cables and for use as
an equipment grounding conductor
-made of steel with protective
coatings or aluminum.
Article 3.44- Rigid Metal Conduit:
Type RMC
3.44.2 Installation
 Uses Permitted
 All atmospheric Condition and
Occupancies
 Corrosion
 Wet location
 Size
 Minimum- RMC smaller than15mm
shall not be used
 Maximum- RMC smaller than
raceway size 150 mm shall not be
used.
Article 3.44- Rigid Metal Conduit:
Type RMC
Reaming and Threading
All cut ends shall be reamed or
otherwise finished to remove
rough edges. Where conduit is
threaded in the field, a standard
cutting 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 section
made of helically wound, formed,
Uses Permitted
to used in exposed and concealed
location
Article 3.48- Flexible Metal Conduit : Type
FMC
3.48.2 Installation
Uses not Permitted
In wet locations
Hoistways, storage battery room
hazardous location
Where exposed to materials having
a deteriorating effect on the
installed conductors, such as oil and
gasoline
Where subject to physical damage
Article 3.50- Liquid Tight Flexible
Metal Conduit: Type FMC
Article 3.50- Liquid Tight Flexible
Metal Conduit: Type LFMC
Liquid tight flexible Metal
Conduit: Type LFMC
- a raceway of circular cross
section having an outer liquid
tight, nonmetallic sunlight
resistant jacket over an inner
flexible metal core with
associated couplings, connectors
and fittings for the insullation of
electric conductors.
Article 3.50- Liquid tight flexible Metal
Conduit: Type LFMC
Uses Permitted
Where conditions of installation,
operation and maintenance require
flexibility or protection from liquids,
vapors or solids
 For direct burial
Uses not permitted
 subject to physical damage
Article 3.50- Liquid tight flexible
Metal 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
3.50.3 Construction Specification
 Marking- conduit suitable for direct burial shall be
so marked.
Article 3.52- Rigid Non metallic
Conduit: Type RNC
Rigid Non metallic Conduit: Type RNC
-A non metallic raceway of circular cross section,
with integral or associated couplings, connectors
and fittings for the installation of electrical
conductors and cables.
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 metallic
conduit: Type RNC
3.52.2 Installation
Uses not permitted
 Hazardous locations
 Support of luminaires
 Physical damage
 Ambient temperature
 Insulation temperature Limitation
Theaters and Similar Locations
Article 3.52- Rigid Non metallic
conduit: Type RNC
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:
Type RNC
Supports
Conduit Raceway Size (mm)
Maximum Spacing Between Supports
(mm)
15-25
900
32-50
1500
65-80
1800
90-125
2100
150
2400
Article 3.52- Rigid Non metallic
conduit: Type RNC
3.52.3 Construction Specification
 RNC and fittings shall be composed of suitable non
metallic material that is resistant to moisture and
chemical atmosphere
 Flame retardant to impact and crushing
 Each length of RNC shall be clearly
and durably
mark 3000 mm
Article 3.53 – High Density Polyethylene
Conduit: Type HDPE Conduit
High Density Polyethylene
Conduit: Type HDPE Conduit
-A non metallic raceway of
circular cross section, with associated
couplings, connectors, and fittings for
the installation of electrical conductors
Article 3.53 – High Density
Polyethylene Conduit: Type HDPE
Conduit3.53.2 Installation
 Uses




Permitted
In discrete lengths from reels
In location subject to severe
corrosive influence
In cinder fill
In direct burial installation on earth
or concrete
Article 3.53 – High Density Polyethylene
Conduit: 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
High Density Polyethylene Conduit:
Type HDPE Conduit
3.53.2 Installation
Size
 Minimum- HDPE conduit smaller
than raceway 15 mm shall not be
used
 Maximum- HPDE conduit larger
than raceway size 100 mm shall not
be used.
Article 3.54- Non metallic underground
conduit conductors: Type NUCC
Non metallic underground conduit
conductors: Type NUCC
-A factory assembly
of conductors or cables inside a
nonmetallic, 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 corrosive
influence
Article 3.54- Non metallic underground
conduit 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 not
damage
Article 3.54- Non metallic underground
conduit conductors: Type NUCC
3.54.2.51 Construction Specification
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
metallic conduit: Type LFNC
 Liquid tight flexible Non
metallic conduit: Type LFNC
-a smooth seamless inner core and
cover bonded together and having one
or more reinforcement layers.
-a smooth inner surface with integral
reinforcement within the
conduit wall, designated as Type
LFNC-B
Article 3.56-Liquid tight flexible Non
metallic conduit: Type LFNC
Uses permitted
 Where flexibility is required for
installation, operation and
maintenance
 Where protection of the contained
conductors is required from vapors,
liquids, solids
 For outdoor location
Article 3.56-Liquid tight flexible Non
metallic conduit: Type LFNC
Uses not permitted:
 Where subject to physical damage
 Where the operating voltage of the
contained conductors is in excess of
600 volts.
Size
Minimum: LFNC smaller than
raceway size 15 shall not be used
Maximum: larger than raceway size
100 mm shall not be used
Article 3.56-Liquid tight flexible Non
metallic conduit: Type LFNC
Bends
Bends in conduit shall be so made that the conduit is not
damae and internal diameter of the conduit is not effectively
reduced
3.56.3 Construction Specification
Construction
shall be provided in continuous length capable of being
shipped in a coil, reel, or carton without damage.
Marking
-shall be marked at least every 600 mm
Article 3.58
Electrical Metallic Tubing:Type EMT
Electrical Metallic Tubing (EMT)
- An unthreaded thin wall raceway of
circular cross section designed for he
physical protection and routing of
conductors and cables and for use as
an equipment grounding conductors
when installed utilizing appropriate
fittings.
Article 3.58
Electrical Metallic Tubing:Type EMT
3.58.2 Installation
Uses Permitted
 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
Electrical Metallic Tubing:Type EMT
Size
 Minimum-EMT smaller than raceway size
15mm shall not be used
 Maximum-shall be raceway size 100mm
3.58.3 Construction Specification
 Construction
 factory threaded integral couplings shall be
permitted, theads should be factory made
 Marking
-EMT shall be clearly and durably marked at least
every 3000mm
Article 3.60
Flexible Metallic Tubing: Type FMT
• Flexible Metallic Tubing (FMT)
- A raceway that is circular in cross section,
flexible, metallic and liquid tight without a
nonmetallic jacket.
Uses Permitted
 In dry location
 Where concealed
 In accessible location
 For system voltage of 1000 volts
maximum
Article 3.60
Flexible Metallic Tubing: Type FMT
Uses not permitted
 In hoistways
Storage battery rooms
Hazardous location
Underground for direct earth burial
Where subject to physical damage
 In lengths over 1800 mm
 Size
Minimum-smaller than raceway size 15 mm
shall not be used
 Maximum-shall be raceway size 20mm
Article 3.62
Electrical Non metallic Tubing:Type ENT
Electrical Non metallic Tubing: Type
ENT
-a non metallic or associated couplings,
connectors, annd fittings for the
installation of electric conductors.
Uses Permitted
In any building not exceeding above grade
as follows
 For exposed work
 Concealed within walls,floors, ceilings.
Article 3.62
Electrical Non metallic Tubing:Type ENT
Uses permitted
 In location subject to corrosive influence and where subject
to chemicals.
 In concealed dry and damp locations
Above suspended ceilings
Uses not permitted
Hazardous locations
 For the support of luminaires and other equipment
Where subject to ambient temperature
For direct earth burial
Article 3.62
Electrical Non metallic Tubing:Type ENT
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
Electrical Non metallic Tubing:Type ENT
3.62.3 Construction Specification
Construction
-ENT shall be made of material that does not exceed the
ignitibility, flammability, smoke generation, and toxicity
characteristic 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 Definition
Metallic Auxiliary Gutters
-Sheet metal enclosure with hinged or
removable covers for housing and protecting
electric wires, cable, and bus bars in which
conductors are laid in place after the wire
ways has been installed as a complete system.
Non Metallic Auxiliary Gutters
-flame retardant, nonmetallic enclosure with
removable covers for housing and protecting
electric wires, cables, and bus bars in which
conductors are laid in place after the wire way
has been installed as a complete system.
Article 3.66-Auxiliary Gutters
Article 3.66-Auxiliary Gutters
3.66.2 Installation
Uses Permitted
 Sheet Metal Auxiliary Gutters
 Non metallic Auxiliary Gutters
 Uses not Permitted
 To enclose switches over current devices, appliances or
other similar equipment.
 To extend a greater distance than 9000mm beyond the
equipment that it suplements.
Article 3.66-Auxiliary Gutters
3.66.3.1 Construction Specification
Construction
 Electrical and mechanical Continuity
 Substantial Construction
 Smooth rounded edges
 Covers
 Clearance of Bare live parts
Article 3.66-Auxiliary Gutters
Markings
 Outdoors
-Suitable for exposure to sunlight
-Suitable for use in wet locations
-Installed conductor insulation temperature rating
 Indoors
 Installed conductor insulation temperature rating
Article 3.68 -Busways
3.6.1.2 Definition
• Busway
- a grounded metal enclosure containing factory mounted bare
or 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
Article 3.68 -Busways
• Uses not Permitted
1. Physical damage
2. Hoistways
3. Hazardous locations
4. Wet locations
5. Working platform
Article 3.68 -Busways
3.68.3 Construction
Markings
-shall be marked with the
voltage and current rating and
with manufacturer’s name /
trademark visible after
installation
Article 3.70-Cable Bus
Cable Bus
-an assembly of insulated conductors
with fittings and condutor terminations
in a completely enclosd, ventilated
protective metal housing.
Use
-permitted at any voltage or current for
which spaced conductors are rated and
shall installed only for exposed work
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 for
which the cablebus is designed, and in no case smaller
than 50 mm^2
ARTICLE 3.72
CELLULAR CONCRETE
FLOOR 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 precast
cellular concrete floor.
ARTICLE 3.72
CELLULAR CONCRETE
FLOOR 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 supplying
ceiling outlets or extensions to the area below the floor
but not above
ARTICLE 3.74 — CELLULAR
METAL
FLOOR RACEWAYS
Cellular Metal Floor Raceway
-The hollow spaces of cellular
metal floors, together with suitable fittings,
that may be approved as enclosures for
electric conductors.
Cell
- A single enclosed tubular space in a cellular
metal floor
member, the axis of the cell being parallel to
the axis of the metal floor member.
ARTICLE 3.74 — CELLULAR
METAL
FLOOR 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 covers
for housing and protecting electric wires and cable and
in which conductors are laid in place af ter the wireway
has been installed as a complete system.
ARTICLE 3.78 — NONMETALLIC
WIREWAYS
3.78.1.2 Definition
 Nonmetallic Wireways
-Flame retardant, nonmetallic troughs
with removable covers for housing and
protecting electric wires and cables in
which conductors are laid in place
after 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 for
aerial 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 or
suspended from a structure, with
associated accessories for the
installation of electrical conductors
and 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 the
installation of electrical conductors.
ARTICLE 3.88 — SURFACE
NONMETALLIC RACEWAYS
Surface Nonmetallic Raceway
-A nonmetallic raceway that is
intended to be mounted to the
surf ace of a structure, with
associated couplings,
connectors, boxes, and fittings
for the installation of electrical
conductors.
ARTICLE 3.90 — UNDERFLOOR
RACEWAYS
Use Permitted
be permitted beneath the surface of
concrete or other flooring material or
in office occupancies where laid fl
ush with the concrete floor and
covered with linoleum or equivalent
floor covering.
ARTICLE 3.92 — CABLE TRAYS
Cable Tray System
-A unit
or assembly of units or
sections and associated fittings
forming a structural system used
to securely fasten or support
cables and raceways.
ARTICLE 3.94 — CONCEALED KNOBAND-TUBE WIRING
3.94.1.2. Definition
Concealed Knob-and-Tube
Wiring
-A wiring method using
knobs, tubes, and flexible
nonmetallic tubing for the
protection and support of
single insulated conductors.
ARTICLE 3.94 — CONCEALED KNOBAND-TUBE WIRING
3.94.2 Installation
Uses Permitted
 For extensions of existing
installations
Elsewhere by special permission
Uses Not Permitted.
 Commercial garages
 Theaters and similar locations
Motion picture studios
Hazardous (classified) locations
ARTICLE 3.96 — MESSENGER
SUPPORTED WIRING
Messenger Supported Wiring
-An exposed wiring support system
using a messenger wire to support
insulated conductors by any one of the
following:
 A messenger with rings and saddles
for conductor support
 A messenger with a field-installed
lashing material for conductor support
 Factory-assembled aerial cable
ARTICLE 398 — OPEN WIRING ON
INSULATORS
3.98.1.2 Definition.
Open Wiring on
Insulators
-An exposed wiring method
using cleats, knobs, tubes,
and flexible tubing for the
protection and support of
single insulated conductors
run in or on buildings.
H
V
D
C
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.
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 function
and 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 range
for fast controlling current
• If alpha increased above a certain predefined maximum value then the tap changer
would 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 proportional
amount 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 which
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 current
or 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 to
control 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 control than characteristic harmonics
system must be provided with dead band. To bring the voltage
back to the reference value and thus avoid hunting, the dead band• These are due to:
should have a width of at least one tap changer step
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 voltage
tap
changer
control
must
be
locked
(generation of
2. firing angle errors
triplen and eve
Harmonics
harmonics and
3. unbalance and distortion of AC Voltages
their analysis is
• Harmonics are electric voltages and currents that appear on the
4.unequal transformer leakage impedances
complex)
electric power system as a result of non-linear electric loads.
• Harmonic instability may occur in high-voltage dc (HVDC) links
due to dynamic interactions between HVDC terminals and the
impedance of the dc lines or cables.
• The harmonics that come from the HVDC will not only increase
loss, thermal stress of equipment, reduce equipment life,•
interference with communications, metering, protection and
control devices to work properly and in some cases, it can even
lead 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 are
always present even under ideal operation• Non Characteristic Harmonics- the harmonics of the order other
The presence of harmonics leads to low system efficiency, poor
power factor, increased loss and reactive power components
from AC and also on the equipment present in the system and
interference on the telecommunication lines.
for reduction of harmonics, filters are used. Here we use a
hybrid configuration of both passive and active filters for
improved power handling capacity of semiconductor devices
and better performance.
• The above circuit diagram consists of a three- phase generator shunt and series. But these filters also have hybrid configuration
source of 345Kv at frequency of 50Hz which is connected to the of passive filters to improve the power handling capacity of
converter transformer for stepping down voltage to 211KV for semiconductor devices.
transmission over long distance. Further a 12-pulse thyristor
bridge converter is connected, which is called as rectifier forharmonic analysis in a basic HVDC transmission system and the
converting AC to DC while the converter at the other end isimportance of using filters for the reduction of the harmonic
referred as inverter for vice-versa conversion. The rectifier-enddistortions in the system to improve the efficiency and reduce
has firing angle (α) control for ignition of the thyristor while thevarious ill effects due to the harmonics.
inverter-end contains the extinction/gamma control (δ).
On observing the various waveforms with and without the
insertion of filters, we may conclude that on connecting the
harmonic filters the voltage values is increased and optimized
while the high current values are reduced.
• A. Three Phase Converter - The converter transformers are
constructed by three phase three winding on same core
material by connecting primary and secondary windings as
either wyes or deltas.
• B. Pulse Generator - a discrete twelve pulse generator is used to
fire the thyristors of HVDC rectifier built with two six pulse
bridges. The four inputs of a pulse generator are alpha firing
angle (in degrees), other three inputs are phase to ground
synchronizing voltages. There are two outputs of a pulse
generator, one connected to wye secondary winding of
transformer and other connected to delta winding of secondary
transformer. Similarly for gamma angle control at the inverterside, a twelve-pulse firing control and discrete gamma
measurement subsystem is used for the two extinction/gamma
angle triggering for the inverter.
• C. Filters - Both the ends have AC filters for reducing the
harmonic distortion in the AC-side of the system and DC filters
or smoothening reactors on the DC line for reducing the ripple
content in the current. The AC filters comprises of both passive
and active components for efficient performance and economy.
Generally the passive filters used are of damped (high-pass) and
tuned (single, double or triple) types while active filters are of