1- Introduction
2- Glossary:
In part one of this subject, I will list all the terms definitions that we can subjected to. These terms will include the following sections:
Definitions for All above terms are included in the below table, please review it very well before we proceed to explain the different properties of conductors.
- Conductors are one of the most important parts of an electrical system. The conductor serves as the highway or path of the electric current. It is essential for this path to be free of obstruction. A damaged conductor can be a hazard to the electrical circuit, to equipment, and to human life.
- In this course, the electrical inspector will learn:
- How to identify conductor color codes, size, ratings and type.
- What to look for when inspecting conductors, including proper termination, bend radius, damaged insulation, and the proper current rating to supply the load.
2- Glossary:
In part one of this subject, I will list all the terms definitions that we can subjected to. These terms will include the following sections:
- Conductor/Cable Terms,
- Conductor/Cable Insulation Materials Terms,
- Conductor/Cable Tests Terms,
- Conductor/Cable Manufacturing Process Terms.
Definitions for All above terms are included in the below table, please review it very well before we proceed to explain the different properties of conductors.
Term
|
Definition
|
1- Conductor/Cable Terms
|
|
Ambient
Temperature
|
Any all-encompassing temperature within a given
area.
|
Ampacity
|
The
maximum current an insulated wire or cable can safely carry without exceeding
either the insulation or jacket material limitations. (Same as Current
Carrying Ampacity)
|
Appliance
Wire and Cable
|
Appliance wiring material is a classification of
Underwriters Laboratories, Inc., covering insulated wire and cable intended
for internal wiring of appliances and equipment.
|
Area
of Conductor
|
The
size of a conductor cross-section, measured in circular mils, square inches,
etc.
|
AWG
|
Abbreviation for American Wire Gauge. A standard
system used in the United States for designing the size of an electrical
conductor based on geometric progression between two conductor sizes. Based
on a circular mil. System 1 mil. Equals .001 inch.
|
Bare
Conductor
|
A
conductor having no covering. A conductor with no coating or cladding on the
copper.
|
Building
Wire
|
Wire used for light and power, 600 volts or less,
usually exposed to outdoor environment.
|
Bunch
Stranding
|
A
group of wire of the same diameter twisted together without a predetermined
pattern.
|
Buried
Cable
|
A cable installed directly into the earth without
use of underground conduit. Also called “direct burial cable”.
|
Bus
|
Wire
used to connect two terminals inside of an electrical unit.
|
Butt
|
Joining of two conductors end to end, with no
overlap and with the axes in line.
|
Butt-Splice
|
A
splice where in two wires from opposite ends butt against each other, or
against a stop, in the center of a splice.
|
Cable
|
A group of individually insulated conductors in
twisted or parallel configuration, with or without an overall coating.
|
Cable
Assembly
|
A
completed cable and its associated hardware ready to install.
|
Cable
Filler
|
The material used in multiple conductor cables to
occupy the spaces formed by the assembly of components, thus forming a core
of the desired shape (normally cylindrical).
|
Cabling
|
The
twisting together of two or more insulated conductors to form a cable.
|
Circular
Mil
|
The area of a circle one mil. (.001”) is diameter,
7,845 x 10-7 sq. inches. Used in expressing wire cross sectional area.
|
Coating
|
A
material applied to the surface of a conductor to prevent environmental
deterioration, facilitate soldering, or improve electrical performance.
|
Coaxial
Cable
|
A cable consisting of two cylindrical conductors
with a common axis, separated by a dielectric.
|
Color
Code
|
A
system for a circuit identification through use of solid colors and
contrasting tracers.
|
Combination
Unilay
|
A stranding configuration that uses two strand sizes
to achieve a 3% reduction in the conductor diameter without compression.
|
Compact
Stranded Conductor
|
A
unidirectional or conventional conductor manufactured to a specified
diameter, approximately 8 to 10% below the nominal diameter of a non-compact
conductor of the same sectional area.
|
Compressed
Stranding
|
A stranding configuration with concentric strands,
in which either all layers or the outer layer only is passed through a die to
reduce the conductor diameter by 3%.
|
Compound
|
An
insulating or jacketing material made by mixing two or more ingredients.
|
Concentric
Stranding
|
A central wire surrounded by one or more layers of
helically wound strands in a fixed, round, geometric arrangement.
|
Concentricity
|
In
a wire or cable, the measurement of the location of the center of the
conductor with respect to the geometric center of the surrounding insulation.
|
Conductivity
|
The capability of a material to carry electrical
current, usually expressed as a percentage of copper conductivity (copper
being 100%).
|
Conductor
|
An
uninsulated wire suitable for carrying electrical current.
|
Control
Cable
|
A multi-conductor cable made for operation in
control or signal circuits.
|
Cord
|
A
small, flexible insulated cable.
|
Core
|
In cables, a component or assembly of components
over which additional components (shields, sheath, etc.) are applied.
|
Cross-Sectional
Area
|
The
area of a conductor exposed by cutting the conductor perpendicular to its
longitudinal plane, expressed in circular mils, square inches, or square
millimeters.
|
Current-Carrying
Capacity
|
The maximum current an insulated conductor or cable
can continuously carry without exceeding its temperature rating. It is also
called ampacity.
|
Derating
Factor
|
A
factor used to reduce the current carrying capacity of a wire when used in
environments other than that for which the value was established.
|
Dielectric
|
Any insulating material between two conductors that
permits electrostatic attraction and repulsion to take place across it.
|
Direct
Burial Cable
|
A
cable installed directly in the earth.
|
Duct
|
An underground or overhead tube for carrying
electrical conductors.
|
Feeder
|
The
circuit conductor between the service equipment and the final branch circuit
over current device.
|
Fixture
Wire
|
A conductor used in lighting or similar equipment or
used to connect a lighting fixture to branch circuit conductors. Common types
include TF, TFN, and TFFN.
|
Flat
Cable
|
A
cable with two smooth or corrugated, but essentially flat surfaces.
|
Flat
Conductor
|
A wire having a rectangular cross section, as
opposed to round or square conductors.
|
Flat
Conductor Cable
|
A
cable with a plurality of flat conductors.
|
Flex
Life
|
The measurement of the ability of conductor or cable
to withstand repeated bending.
|
Flexible
|
The
quality of a cable or cable component that allows for bending under the
influence of outside force, as opposed to limpness which is bending due to
the cable’s own weight.
|
Flexibility
|
The ease with which a cable may be bent.
|
Gauge
|
A
term used to denote the physical size of a wire.
|
Hard
Drawn Copper Wire
|
Copper wire that has not been annealed after
drawing.
|
Hook-Up
Wire
|
A
single insulated conductor used for low current, low voltage (usually under
600 volts) applications within enclosed electronic equipment.
|
Insulation
|
A material having high resistance to the flow of
electric current. Often called a dielectric in radio frequency cable.
|
Insulation
Level-100%
|
Cable
for use on grounded systems or where the system is provided with relay
protection such that ground faults will be cleared as rapidly as possible but
in any case within one minute.
|
Insulation
Level-133%
|
Cable for use on grounded systems or where the
faulted section will be de-energized in a time not exceeding one hour.
|
Insulation
Resistance (I.R)
|
The
resistance offered by insulation to an impressed DC voltage, tending to
produce a leakage current through the insulation.
|
Insulation
Thickness
|
The wall thickness of the applied insulation.
|
Jacket
|
An
outer covering, usually nonmetallic, mainly used for protection against the
environment.
|
Kcmil
|
1,000
circular mils.
|
Leakage
Current
|
The
undesirable flow of current through or over the surface of insulation.
|
Listed
|
Conductors or other equipment included in a list
published by a nationally recognized testing laboratory.
|
MC
Metal-Clad Cable
|
MEC
type designation for power and control cables enclosed in a smooth metallic
sheath, or interlocking tape armor.
|
MCM
|
One thousand circular mils.
|
Member
|
A
group of insulated wires to be cabled with other stranded groups into
multiple membered cable.
|
Messenger
|
The linear supporting member, usually a high
strength steel wire, used as the supporting element of a suspended aerial
cable. The messenger may be an integral part of the cable or exterior to it.
|
Metal-Clad
Cable
|
Type
MC; a multi-conductor cable, similar to type AC, in which the conductors are
twisted together under aluminum or steel armor. With or without an overall
PVC covering.
|
Mil
|
A unit used in measured diameter of a wire or
thickness of insulation over a conductor. One one-thousandth of an inch
(.001”).
|
Multi-Conductor
|
More
than one conductor within a single cable complex.
|
Rated
Temperature
|
The maximum temperature at which an electric
component can operate for extended periods without undue degradation or
safety hazard.
|
Rated
Voltage
|
The
maximum voltage at which an electric component can operate for extended
periods without loss of its basic properties.
|
Rope
Strand
|
A conductor whose cross-section is substantially
circular.
|
Semi-Conducting
Tape
|
A
tape of such resistance that when applied between two elements of a cable,
the adjacent surfaces of the two elements will maintain substantially the
same potential.
|
Separator
|
A layer of insulating material such as textile,
paper, polyester, etc. Used to improve stripping qualities, flexibility, mechanical
or electrical protection to the components.
|
Sheath
|
The
outer covering or jacket of a multi-conductor cable.
|
Shield
|
A metallic layer placed around a conductor or group
of conductors to prevent electrostatic interference between the enclosed wires
and external fields.
|
Skin
Effect
|
The
tendency of alternating current, as its frequency increases, to travel only
on the surface of a conductor.
|
Solid
Conductor
|
A single unit not divided into parts.
|
Strand
|
A
single uninsulated wire.
|
Stranded
Conductor
|
A conductor composed of individual groups of wires
twisted together to form an entire unit.
|
Temperature
Rating
|
The
maximum temperature at which an insulating material may be used in continuous
operation without loss of its basic properties.
|
Tensile
Strength
|
The pull stress required to break a given specimen.
|
Test
Lead
|
A
flexible insulated lead wire used for making tests, connecting instruments to
a circuit temporarily or for making temporary electrical connections.
|
Thermal
Rating
|
The maximum and/or minimum temperature at which a
material will perform its function without undue degradation.
|
Tinned
Copper
|
Tin
coating added to copper to aid in soldering and inhibit corrosion.
|
Tray
Cable
|
A factory assembled multi-conductor or multi-pair control,
signal or power cable specifically approved under the National Electrical
Code for installation trays.
|
UF
|
Thermoplastic
underground feeder and branch circuit cable.
|
USE
|
Underground Service Entrance cable,
rubber-insulated, neoprene or XLP jacketed.
|
Voltage
Drop
|
The
amount of voltage loss from original input in a conductor of given size and
length or over a connection such as a termination.
|
Voltage
Levels
|
Power-limited 0-300 volts. Low voltage 600-2000
volts. Medium voltage 5000-69000 volts.
|
High
Voltage
|
Generally,
a wire or cable with an operating voltage of over 35,000 volts.
|
Voltage
Rating
|
The highest voltage that may be continuously applied
to a wire in conformance with standards or specifications.
|
VW-1
|
A
flammability rating established by Underwriters Laboratories for wires and
cables that pass a specially designated vertical flame test, formerly
designated FR-1. Multi-conductor flat or round portable power cables without
grounding conductor.
|
Water
Absorption
|
Water by percent weight absorbed by a material after
a given immersion period.
|
Wire
|
A
single conductor, typically with a covering of insulation.
|
Wire
Gauge
|
A
measure of the diameter or size of wires. The sizes are expressed by numbers.
|
Yield
Strength
|
The
minimum stress at which a material will start to physically deform without
further increase in load.
|
2- Insulation
Materials Terms
|
|
CPE
|
Jacketing
compound based on chlorinated polyethylene.
|
Ethylene
Propylene Rubber (EPR)
|
An ozone-resistant rubber consisting primarily of
ethylene propylene copolymer (EPM) or ethylene diene terpolymer (EPDM).
|
Flame
Retardant
|
A
chemical added in insulation materials to make them less combustible, such as
antimony oxide (to PVC) or alumna trihydrate.
|
Flame
Resistance
|
The ability of a material to restrict the spread of
combustion to a low rate of travel, so that the flame will not be conveyed.
|
MTW
|
Thermoplastic-insulated
machine tool wire. 90°C to 105°C, 600V.
|
Nylon
|
A group of polyimide polymers that are used for wire
and cable jacket.
|
Non-Contaminating
PVC
|
A
polyvinyl chloride formulation that does not produce electrical contamination
through plasticizer migration.
|
Plasticizer
|
A chemical agent added to plastics to make them
softer and more pliable.
|
Polyester
|
Polyethylene
terephtalate that is used extensively in the production of a high strength,
moisture resistant film used as a cable core wrap.
|
Polyethylene
|
A thermoplastic material having the chemical
identity of polymerized ethylene.
|
Polymer
|
A
substance made of many repeating chemical units or molecules. The term
polymer is often used in place or plastic, rubber or elastomer.
|
Polypropylene:
|
A thermoplastic polymer of propylene.
|
Polyvinyl
Chloride (PVC)
|
A
thermoplastic material composed of polymers of vinyl chloride, which may be
rigid or elastomeric, depending on specific formulation.
|
PPE
|
Portable Power Elastomer. Same as Type W, except
that it is a thermoplastic elastomer insulation and jacket, whereas Type W is
all thermostat.
|
Primary
Insulation
|
The
first layer of non-conductive material applied over a conductor, whose prime
function is to act as electrical insulation.
|
PVC
|
Polyvinyl chloride, a common thermoplastic
insulation and jacketing material for building wire and cable.
|
RH
|
Type
RH, a rubber or XLP-insulated conductor for use at 75°C in dry locations.
|
RHH
|
Type RHH, a rubber or XLP- insulated conductor for
use at 90°C in dry locations.
|
RHW
|
Type
RHW, a rubber or XLP-insulated conductor for use at 75°C in dry and wet
locations.
|
RHW-2
|
Type RHW-2, a rubber or XLP-insulated conductor for
use at 90°C in dry and wet locations.
|
Secondary
Insulation
|
A
high-resistance dielectric material whose flame is placed over primary
insulation to protect it from abrasion.
|
Self-Extinguishing
|
The characteristic of a material whose flame is
extinguished after the igniting flame is removed.
|
SIS
|
Indicates
single conductor having synthetic thermosetting insulation of heat resistant,
moisture resistant, flame retarding grade. Also made with chemically
cross-linked polyethylene insulation. Used for switchboard wiring only, 90°C.
|
SJ-SJE
|
Junior hard service, rubber insulated pendant or
portable cord. Same construction as type S, but 300B. Jacket thickness
different.
|
SJO-SJEO
|
Same
as SJ, but neoprene, oil resistant compound outer jacket, 300V, 60°C
|
SJOOW-SJEOOW
|
Same as type SJO, except oil resistant insulation
and oil and weather resistant jacket.
|
SJT
|
Junior
hard service, thermoplastic or rubber insulated conductors with overall thermoplastic
jacket. 300V, 60C to 105C.
|
SJTO
|
Same as SJT, but oil resistant thermoplastic outer
jacket. 60C
|
SO-SEO
|
Hard
service cord, same construction as type S, except oil resistant neoprene
jacket, 600V, 60°C to 90C
|
SOOW
|
Service cord with oil resistant jacket, oil
resistant and insulation and weather resistant. Also is water resistant.
600V.
|
ST
|
Hard
service, jacketed, same as type S, except all plastic construction. 600V,
60°C to 105°C.
|
Stabilizer
|
A metallic compound added to PVC to maintain the
integrity of the insulation compound during processing and use.
|
STO
|
Same
as ST, but with oil resistant, thermoplastic outer jacket. 600V, 60°C.
|
STOW/STOW
|
Service cord with oil resistant, thermoplastic
jacket and weather resistant. STOW meets CSA approval for outdoor use. Can be
water resistant. UL 600V.
|
STW/STW
|
Service
cord with thermoplastic and weather resistant jacket, but not oil resistant.
Can be UL water resistant. STW meets CSA approval for outdoor use. 600V.
|
Sunlight
Resistance
|
The ability of a conductor or cable insulation to
resist degradation caused by exposure to ultraviolet rays.
|
TEW
|
Canadian
Standards Association type appliance wires. Solid or stranded single
conductor, plastic insulated. 600V, 105C.
|
TFFN
|
Fixture wire; thermoplastic covered, stranded with a
nylon sheath. 90C.
|
THHN
|
90C,
600V, nylon-jacketed building wire for dry and damp locations.
|
THHN-2
|
Incorrect reference, commonly misapplied when THWN-2
is called out.
|
THW
|
Thermoplastic,
vinyl insulated building wire. Flame retardant, moisture and heat resistant.
75°C. Dry and wet locations.
|
THWN
|
75°C, 600V, nylon jacketed building wire for dry or
wet locations.
|
THWN-2
|
90°C,
600V, nylon-jacketed building wire for dry or wet locations.
|
XHHW-2
|
High temperature (90°C), chemically cross-linked,
polyethylene jacketed, small diameter building wire.
|
XLP
|
Cross-linked
polyethylene.
|
3- Conductor/Cable Tests Terms
|
|
Continuity
Check
|
A
test to determine whether electrical current flows continuously throughout
the length of a single wire or individual wires in a cable.
|
Dielectric
Test
|
A test in which a voltage higher than the rated
voltage is applied for a specified time to determine the adequacy of the
insulation under normal conditions.
|
Flammability
Test
|
A
test to determine the ability of a cable to resist ignition when placed near
a source of heat or flame and to self extinguish when removed from this
source.
|
Heat
Shock
|
A test to determine stability of a material by
sudden exposure to a high temperature for a short period of time.
|
Hi
Pot
|
A
test designed to determine the highest voltage that can be applied to a
conductor without electrically breaking down the insulation.
|
Life
Cycle
|
A test to determine the length of time before
failure in a controlled, usually, accelerated environment.
|
Megohommeter
|
A
testing device that applied a DC voltage to a conductor and measures the
resistance (in millions of ohms) offered by the conductors insulation.
|
Spark
Test
|
A test designed to locate imperfections (usually
pin-holes) in the insulation of a wire or cable by application of a voltage
for a very short period of time while the wire is being drawn through the
electrode field.
|
Tank
Test
|
A
voltage dielectric test in which the test sample is submerged in water and
voltage is applied between the conductor and water as ground.
|
4- Manufacturing
Process Terms
|
|
Anneal
|
The
process of controlled heating and cooling of a metal to achieve predetermined
characteristics as to tensile strength and elongation. . Annealing copper
renders it less brittle.
|
Drawing
|
In wire manufacturing, pulling the metal through a
die or series of dies to reduce diameter to a specified size.
|
Extrusion
|
The
process of continuously forcing both a plastic or elastomer and a conductor
core through a die, thereby applying a continuous coating of insulation or
jacket to the core or conductor.
|
Oxidation
|
The process of uniting a compound with oxygen,
usually resulting in an unwanted surface degradation of the material or compound.
|
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