Title The Wire and Cable Technical Information Handbook Electric Current Volt Wire Electrical Conductor Polyethylene 2.2 MB 313
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##### Document Text Contents
Page 1

1. BASIC PRINCIPLES
OF ELECTRICITY
1.1 Electricity 2

1.2 The Volt 2

1.3 The Ampere 2

1.4 The Ohm 2

1.5 Ohm’s Law 2

1.6 Ampacity 3

1.7 Electrical Systems 3

1. Basic Principles of Electricity|

| 1

Page 2

2 |

1.1 ELECTRICITY

Electricity, simply put, is the flow of electric current along a conductor. This electric current takes the form of free electrons that transfer from one atom to
the next. Thus, the more free electrons a material has, the better it conducts. There are three parameters involved in the electrical equation: the volt, the
ampere and the ohm.

1.2 THE VOLT

The pressure that is put on free electrons that causes them to flow is known as electromotive force (EMF). The volt is the unit of pressure, i.e., the volt is the
amount of electromotive force required to push a current of one ampere through a conductor with a resistance of one ohm.

1.3 THE AMPERE

The ampere defines the flow rate of electric current. For instance, when one coulomb (or 6 � 10
18

electrons) flows past a given point on a conductor in
one second, it is defined as a current of one ampere.

1.4 THE OHM

The ohm is the unit of resistance in a conductor. Three things determine the amount of resistance in a conductor: its size, its material, e.g., copper or
aluminum, and its temperature. A conductor’s resistance increases as its length increases or diameter decreases. The more conductive the materials used,
the lower the conductor resistance becomes. Conversely, a rise in temperature will generally increase resistance in a conductor.

1.5 OHM’S LAW

Ohm’s Law defines the correlation between electric current (I), voltage (V), and resistance (R) in a conductor. Ohm’s Law can be expressed as:

V = I � R

Where: V � volts
I � amps
R � ohms

|1. Basic Principles of Electricity

Page 156

10. Packaging of Wire and Cable|

| 165

40 42 48 54 60 66 72 78 84 90 96

30 26 36 32 28 36 36 48 54 54 54

16 24 24 24 28 36 36 42 48 48 56

2 2 2 3 3 3 3 3 3 3 3

32,698 23,651
22,707 16,424 35,632 40,243 43,445
16,682 12,067 26,179 29,566 31,919 44,350

12,773 9,239 20,043 22,637 24,438 33,955 45,097
10,092 7,300 15,836 17,886 19,309 26,829 35,632
8,174 5,913 12,828 14,488 15,640 21,731 28,862 43,010

6,756 4,887 10,601 11,973 12,926 17,960 23,853 35,545 44,198
5,677 4,106 8,908 10,061 10,861 15,091 20,043 29,868 37,139 46,688 48,771
4,837 3,499 7,590 8,573 9,255 12,859 17,078 25,450 31,645 39,782 41,557

4,171 3,017 6,545 7,392 7,980 11,087 14,725 21,944 27,285 34,302 35,832
3,633 2,628 5,701 6,439 6,951 9,658 12,828 19,116 23,769 29,881 31,214
3,193 2,310 5,011 5,659 6,110 8,489 11,274 16,801 20,890 26,262 27,434

2,829 2,046 4,439 5,013 5,412 7,519 9,987 14,882 18,505 23,263 24,301
2,523 1,825 3,959 4,471 4,827 6,707 8,908 13,275 16,506 20,750 21,676
2,264 1,638 3,553 4,013 4,333 6,020 7,995 11,914 14,814 18,624 19,454

2,044 1,478 3,207 3,622 3,910 5,433 7,215 10,752 13,370 16,808 17,558
1,341 2,909 3,285 3,547 4,928 6,545 9,753 12,127 15,245 15,925
1,222 2,650 2,993 3,231 4,490 5,963 8,886 11,049 13,891 14,510

1,118 2,425 2,739 2,957 4,108 5,456 8,130 10,110 12,709 13,276
1,027 2,227 2,515 2,715 3,773 5,011 7,467 9,285 11,672 12,193
946 2,052 2,318 2,502 3,477 4,618 6,882 8,557 10,757 11,237

875 1,898 2,143 2,314 3,215 4,270 6,362 7,911 9,945 10,389
811 1,760 1,987 2,145 2,981 3,959 5,900 7,336 9,222 9,634
754 1,636 1,848 1,995 2,772 3,681 5,486 6,821 8,575 8,958

703 1,525 1,723 1,860 2,584 3,432 5,114 6,359 7,994 8,351
657 1,425 1,610 1,738 2,415 3,207 4,779 5,942 7,470 7,803

1,628 2,261 3,003 4,476 5,565 6,996 7,308

1,527 2,122 2,819 4,200 5,223 6,566 6,858
1,436 1,996 2,650 3,949 4,911 6,174 6,449
1,353 1,880 2,497 3,721 4,626 5,816 6,075

Continued on next page >>

Page 157

Table 10.2–Capacities of Typical Shipping Reels per NEMA WC 26 (Continued)

C
ab

le
O

D
(

in
.)

|10. Packaging of Wire and Cable

166 |

The following formula from NEMA WC 26 can be used to
calculate approximate cable capacity per reel:

Footage =
0.262 � T � (H � C) � (D � H � C)

(Wire OD)
2

Flange Dia. (in.) 16 16 20 24 24 24 28 30 32 36

Traverse (in.) 10 12 12 12 12 16 18 18 24 24

Drum Dia. (in.) 12 6 8 10 12 10 12 12 16 16

Clearance (in.) 1 1 1 1 1 1 1 2 2 2

1.75
1.80
1.85

1.90
1.95
2.00

2.05
2.10
2.15

2.20
2.25
2.30

2.35
2.40
2.45

2.50
2.55
2.60

2.65
2.70
2.75

2.80
2.85
2.90

2.95
3.00
3.05

3.10
3.15
3.20

3.25
3.30
3.35

3.40
3.45
3.50

Page 312

|Glossary

330 |

UNIDIRECTIONAL STRANDING – A term denoting that in a stranded conductor all
layers have the same direction of lay.

UNILAY – More than one layer of helically laid wires with the direction of lay and
length of lay the same for all layers. See Concentric-lay Conductor.

USE – A UL cable type. Underground service entrance cable, XLP or rubber-insulated,
Hypalon or XLP jacketed.

UTP – Unshielded Twisted Pair. Two wires, usually twisted around each other to help
cancel out induced noise in adjacent circuits. An unshielded twisted-pair cable usually
contains four pairs in a single cable jacket.

V

V – Volts. The SI unit of electrical potential difference. One volt is the difference in
potential between two points of a conducting wire carrying a constant current of one
ampere when the power dissipated between these two points is equal to one watt.

VA – Volt-ampere. A designation of power in terms of volts and amperes.

VAR – A unit of reactive power that means volt-amperes, reactive.

VAR METER – An instrument used by power companies to measure the
kvar consumption.

V BAND – A band of frequencies between 46 and 56 gigahertz.

VC – Varnished-cambric insulation.

VCSEL – Vertical-cavity surface-emitting laser is a type of semiconductor laser
diode operating in the 850 nm wavelength window that is commonly used in
Ethernet-based networks.

VDE – Association of German Electrical Engineers.

VELOCITY OF PROPAGATION – The transmission speed of an electrical signal down a
length of cable compared to its speed in free space. Usually expressed as a percentage.

VG – Varnished-glass or nylon braid, 600 V or 3,000 V, 130°C.

VHF – Very high frequency, the band extending from 30 to 300 MHz
(television channels 2 to 13 and most FM radio) as designated by the Federal
Communications Commission.

VIDEO PAIR CABLE – A transmission cable containing low-loss pairs with an
impedance of 125 ohms. Used for TV pick ups, closed-circuit TV, telephone carrier
circuits, etc.

VISCOSITY – Internal friction or resistance to flow of a liquid: the constant ratio of
shearing stress to rate of shear.

VLF – Very low frequencies, the band extending from 10 to 30 kHz, as designated by
the Federal Communications Commission.

VOICE FREQUENCY (VF) – Describes an analog signal within the range of transmitted
speech, typically supported by an analog telecommunications circuit.

VOLT – A unit of electrical “pressure.” One volt is the amount of pressure that will
cause one ampere of current to flow through one ohm of resistance.

VOLTAGE – Electrical potential or electromotive force expressed in volts.

VOLTAGE BREAKDOWN – A test to determine the maximum voltage insulated wire can
withstand before failure.

VOLTAGE, CORONA EXTINCTION – The minimum voltage that sustains corona
(partial discharge), determined by applying a corona producing voltage, then decreasing
the voltage until corona is extinct.

VOLTAGE DIVIDER – A network consisting of impedance elements connected in series
to which a voltage is applied and from which one or more voltages can be obtained
across any portion of the network.

VOLTAGE DROP – The voltage developed across a conductor by the current and the
resistance or impedance of the conductor.

VOLTAGE, INDUCED – A voltage produced in a conductor by a change in magnetic flux
from an outside source.

VOLTAGE RATING – The highest voltage that may be continuously applied to a wire
or cable in conformance with standards or specifications.

VOLTAGE STANDING WAVE RATIO (VSWR) – The ratio of the maximum effective
voltage to the minimum effective voltage measured along the length of a mismatched

VOLTAGE TO GROUND – The voltage between an energized conductor and earth.

VOLUME RESISTIVITY – The resistance in ohms of a body of unit length and unit
cross-sectional area.

VULCANIZATION – A chemical reaction in which the physical properties of a polymer
are changed by reacting it with cross-linking agents.

VW-1 – Vertical wire flame test. Formerly designated as FR1. A UL fire rating for single
conductor cables. The test is described in UL Standard 1581.

W

W – (1) Symbol for watt or wattage, (2) A UL cable type. Heavy duty portable power
cable, one to six conductors. 600 V, without grounds.

WALL THICKNESS – The thickness of the applied insulation or jacket.

WATER ABSORPTION – A test to determine the amount of water absorbed by a
material after a given immersion period.

WATER BLOCKED CABLE – A multiconductor cable having interstices filled with
a water-blocking compound to prevent water flow or wicking.

WATER COOLED LEADS – Furnace Cables. High Energy Cables. Usually welding cable
strands cabled with a hose core for carrying coolant – used in heavy duty welding
equipment, electric furnace applications, plating and various chemical processes.

WATER TREEING – A type of insulation deterioration that can occur after long term
immersion in water with an electrical stress applied.

WATERFALL – The point at which cables installed horizontally in a tray transition
to a vertical section of tray.

WATT – A unit of electrical power. One watt is equivalent to the power represented
by one ampere of current under a pressure of one volt in a DC circuit.

Page 313

Glossary|

| 331

WAVEFORM – A graphical representation of a varying quantity. Usually, time is
represented on the horizontal axis and the current or voltage value is represented
on the vertical axis.

WAVE FRONT – (1) That portion of an impulse (in time or distance) between the
10 percent point and the point at which the impulse reaches 90 percent of crest value,
(2) the rising part of an impulse wave.

WAVELENGTH – The distance between the nodes of a wave. The ratio of the velocity
of the wave to the frequency of the wave.

WAVESHAPE REPRESENTATION – The designation of current or voltage by a
combination of two numbers. For other than rectangular impulses: (a) virtual duration
of the wave front in microseconds, (b) time in microseconds from virtual zero to the
instant at which one-half of the crest value is reached on the tail. For rectangular
impulses: (a) minimum value of current or voltage, (b) duration in microseconds.

WEEE – Waste Electrical and Electronic Equipment. A European requirement that
promotes the recycling of obsolete electrical equipment. Also see RoHS.

WEIGHT RESISTIVITY – The resistance in ohms at a specified temperature of a copper
wire of uniform cross section and of unit weight and unit length.

WELDING – Joining the ends of two wires, rods, or groups of wires (a) by fusing, using
the application of heat or pressure or both, by means of a flame torch, electric arc, or
electric current or (b) by cold pressure.

WHEATSTONE BRIDGE – A device used to measure DC resistance. See Bridge.

WICKING – The longitudinal flow of a liquid in a wire or cable due to capillary action.

WIRE – A rod or filament of drawn or rolled metal whose length is great in comparison
with the major axis of its cross section.

WIRE BRAID – Flexible wire constructed of small size strands in tubular form. Used for
shielding or connections where constant flexing is required.

WIRE GAUGE (AWG) – The American Wire Gauge, originally called Brown & Sharpe
Gauge. A system of numerical wire sizes starting with the lowest numbers for the largest
sizes. Gauge sizes are each 20.6 percent apart based on the cross-sectional area.

WIRE NUT – A closed-end splice that is screwed on instead of crimped.

WIRE-WRAPPED CONNECTION – A solderless connection made by wrapping bare
wire around a square or rectangular terminal with a power or hand tool.

WIRE WRAPPING TOOLS – Portable electric tools and automatic stationary machines
used to make solderless wrapped connections of wires to terminals.

WITHSTAND TEST VOLTAGE – The voltage that the device must withstand without
flashover, disruptive discharge, puncture, or other electric failure when voltage is applied
under specified conditions.

WP – Weatherproof construction for overhead wires.

WORKSTATION – (1) Input/Output equipment at which an operator works; (2) a station
at which a user can send data to, or receive data from, a computer or other workstation
for the purpose of performing a job.

WRAPPER – An insulating barrier applied as a sheet of tape wrapped around a
coil periphery.

X

X – Symbol for reactance.

X BAND – A band of frequencies between 5,200 and 10,000 megahertz.

XHHW – A UL cable type. Cross-linked polyethylene insulated small diameter building
wire rated 75°C wet and 90°C dry.

XHHW-2 – A UL cable type. Cross-linked polyethylene insulated small diameter
building wire rated 90°C wet and dry.

XLP – Cross-linked polyethylene. Also written XLPE.

Y

YIELD STRENGTH – The point at which a substance changes from elastic to viscous.

Z

Z – Symbol for impedance.

ZETABON – Dow’s trade name for an acrylic acid copolymer coated aluminum tape.

ZIPPER TUBING – Alpha’s trade name for harnessing/jacketing material containing
a zipper-track type closure. The zipper arrangement allows installation with no need
to disconnect installed wire. See Loc-Trac.

ZYTEL – DuPont’s trademark for nylon resins.