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Section 16 Technical Information and Glossary

Conductors..................................................................................................................................................16.1?16.7 Insulation and Jacket Materials....................................................................................................................16.8?16.25 Shields.........................................................................................................................................................16.26?16.28 Maximum Short Circuit Current.....................................................................................................................16.29?16.30 Installation and Testing................................................................................................................................16.31?16.44 Packaging of Wire and Cable.........................................................................................................................16.45?16.48 Conversion Tables.........................................................................................................................................16.49?16.50 Glossary.......................................................................................................................................................16.51?16.80

Technical Information and Glossary

Technical Information

Technical Information

Conductors

CONDUCTORS

The conductor is the metallic component of cables through which electrical power or electrical signals are transmitted. Conductor size is usually specified by American Wire Gauge (AWG), circular mil area or in square millimeters.

AWG The American Wire Gauge (sometimes called Brown and Sharpe or B and S) is used almost exclusively in the USA for copper and aluminum wire. The Birmingham Wire Gauge (BWG) is used for steel armor wire.

The diameters according to the AWG are defined as follows: the diameter of size 4/0 (sometimes written 0000) equals 0.4600 inch and that of size #36 equals 0.0050 inch; the intermediate sizes are found by geometric progression. That is, the ratio of the diameter of one size to that of the next smaller size (larger gauge number) is:

39

_0_.4_6_00_ 0.0050

=

1.122932

Circular Mil Siz_4es larger than 4/0 are specified in terms of the total area of a cross-section of the copper in circular mils (cmil). A circular mil is a unit of area equal to the area of a circle one mil in diameter. It is p/4 (equal to 0.7854) of a square mil (one mil 5 0.001 inch). The area of a circle in circular mils is therefore equal to the square of its diameter in mils. A solid wire one inch in diameter has an area of 1,000,000 cmils, whereas one square inch equals 4/p 3 1,000,000 cmils (equal to 1,273,200 cmils).

Square Millimeters Metric sizes are given in terms of square millimeters (mm2).

Conductor Characteristics Relative electrical and thermal conductivities of common metal conductors are as follows:

Table 1?Relative electrical and thermal conductivities of common conductor materials

Metal

Relative Electrical Conductivity at 20?C

Relative Thermal Conductivity at 20?C

Silver

106

108

Copper (annealed)

100

100

Copper (hard drawn)

97

?

Gold

72

76

Aluminum

62

56

Magnesium

39

41

Zinc

29

29

Nickel

25

15

Cadmium

23

24

Cobalt

18

17

Iron

17

17

Platinum

16

18

Tin

15

17

Steel

12

?

Lead

8

9

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Technical Information

Conductors

Strand Types

Concentric Strand

A concentric stranded conductor consists of a central wire or core surrounded by one or more layers of helically-laid wires. Each layer after the first has six more wires than the preceding layer. Except in compact stranding, each layer is usually applied in a direction opposite to that of the layer under it. If the core is a single wire and if it and all of the outer strands have the same diameter, the first layer will contain six wires; the second, twelve; the third, eighteen; etc.

Bunch Strand

The term bunch stranding is applied to a collection of strands twisted together in the same direction without regard to the geometric arrangement.

Rope Strand

A rope stranded conductor is a concentric stranded conductor each of whose component strands is itself stranded. A rope stranded conductor is described by giving the number of groups laid together to form the rope and the number of wires in each group.

Sector Conductor

A sector conductor is a stranded conductor whose cross-section is approximately the shape of a sector of a circle. A multiple-conductor insulated cable with sector conductors has a smaller diameter than the corresponding cable with round conductors.

Segmental Conductor

A segmental conductor is a round, stranded conductor composed of three or four sectors slightly insulated from one another. This construction has the advantage of lower AC resistance (less skin effect).

Annular Conductor

An annular conductor is a round, stranded conductor whose strands are laid around a suitable core. The core is usually made wholly or mostly of nonconducting material. This construction has the advantage of lower total AC resistance for a given cross-sectional area of conducting material by eliminating the greater skin effect at the center.

Compact Strand

A compact stranded conductor is a round or sector conductor having all layers stranded in the same direction and rolled to a predetermined ideal shape. The finished conductor is smooth on the surface and contains practically no interstices or air spaces. This results in a smaller diameter.

Figure 1?Concentric strand Figure 2?Bunch strand Figure 3?Rope strand

Figure 4?Sector conductor Figure 5?Segmental conductor Figure 6?Annular conductor

Figure 7?Compact strand

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Technical Information

Technical Information

Conductors

Compressed Strand

Compressed conductors are intermediate in size between standard concentric conductors and compact conductors. A comparison is shown below:

Solid

Compact

Compressed

Concentric

Figure 8?Comparative sizes and shapes of 1,000 kcmil conductors

In a concentric stranded conductor, each individual wire is round and considerable space exists between wires. In a compressed conductor, the conductor has been put through a die that "squeezes out" some of the space between wires. In a compact conductor each wire is preformed into a trapezoidal shape before the wires are stranded together into a finished conductor. This results in even less space between wires. A compact conductor is, therefore, the smallest in diameter (except for a solid conductor, of course). Diameters for common conductor sizes are given in the table below.

Table 2?Diameters for copper and aluminum conductors

Conductor Size

(AWG)

(kcmil)

Solid

8

16.51

6

26.24

4

41.74

0.1285 0.1620 0.2043

3

52.62

2

66.36

1

83.69

0.2294 0.2576 0.2893

1/0

105.6

2/0

133.1

3/0

167.8

0.3249 0.3648 0.4096

4/0

211.6

?

250

?

300

0.4600 0.5000 0.5477

?

350

?

400

?

450

?

500

?

550

?

600

?

650

?

700

?

750

0.5916 0.6325 0.6708

0.7071 0.7416 0.7746

0.8062 0.8367 0.8660

?

800

?

900

?

1,000

0.8944 0.9487 1.0000

Sources: ASTM B8 and B496 ICEA S-95-658 (NEMA WC-70)

Nominal Diameters (in.)

Class B Compact

Class B Compressed

0.134

0.141

0.169

0.178

0.213

0.225

0.238

0.252

0.268

0.283

0.299

0.322

0.336

0.361

0.376

0.406

0.423

0.456

0.475

0.512

0.520

0.558

0.570

0.611

0.616

0.661

0.659

0.706

0.700

0.749

0.736

0.789

0.775

0.829

0.813

0.866

0.845

0.901

0.877

0.935

0.908

0.968

0.938

1.000

0.999

1.061

1.060

1.117

Class B Concentric

0.146 0.184 0.232

0.260 0.292 0.332

0.373 0.419 0.470

0.528 0.575 0.630

0.681 0.728 0.772

0.813 0.855 0.893

0.929 0.964 0.998

1.031 1.093 1.152

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Conductors

Coatings

There are three materials commonly used for coating a copper conductor. These are tin, silver and nickel.

Tin is the most common and is used for improved corrosion resistance and solderability.

Silver plated conductors are used in high-temperature environments (150?C?200?C). It is also used for high-frequency applications where silver's high conductivity (better than copper) and the "skin effect" work together to reduce attenuation at high frequencies.

Nickel coatings are used for conductors that operate between 200?C and 450?C. At these high temperatures, copper oxidizes rapidly if not nickel plated. One drawback of nickel, however, is its poor solderability.

Class B, C and D Copper Strand

Technical Information

Table 3?Class B concentric-lay-stranded copper conductors

Size

Number of Wires

(AWG or kcmil)

5,000

217

4,500

217

4,000

217

3,500

169

3,000

169

2,500

127

2,000

127

1,900

127

1,800

127

1,750

127

1,700

127

1,600

127

1,500

91

1,400

91

1,300

91

1,250

91

1,200

91

1,100

91

1,000

61

900

61

800

61

750

61

700

61

650

61

600

61

550

61

500

37

450

37

400

37

350

37

300

37

250

37

4/0

19

Diameter

of Each Strand

Weight

(mils)

(lb. /1,000 ft.)

151.8

15,890

144

14,300

135.8

12,590

143.9

11,020

133.2

9,353

140.3

7,794

125.5

6,175

122.3

5,866

119.1

5,558

117.4

5,402

115.7

5,249

112.2

4,940

128.4

4,631

124.0

4,323

119.5

4,014

117.2

3,859

114.8

3,705

109.9

3,396

128.0

3,088

121.5

2,779

114.5

2,470

110.9

2,316

107.1

2,161

103.2

2,007

99.2

1,853

95.0

1,698

116.2

1,544

110.3

1,389

104.0

1,235

97.3

1,081

90.0

926.3

82.2

711.9

105.5

653.3

Nominal Overall Diameter

(in.)

2.58 2.45 2.31

2.16 2.00 1.82

1.63 1.59 1.55

1.53 1.50 1.46

1.41 1.36 1.32

1.30 1.26 1.21

1.15 1.09 1.03

1.00 0.964 0.929

0.893 0.855 0.813

0.772 0.728 0.681

0.630 0.575 0.528

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Table 3?Class B concentric-lay-stranded copper conductors (continued)

Size

Number of Wires

(AWG or kcmil)

3/0

19

2/0

19

1/0

19

1

19

2

7

3

7

4

7

5

7

6

7

7

7

8

7

9

7

10

7

12

7

14

7

16

7

18

7

20

7

Diameter

of Each Strand

Weight

(mils)

(lb. /1,000 ft.)

94.0

518.1

83.7

410.9

74.5

325.8

66.4

258.4

97.4

204.9

86.7

162.5

77.2

128.9

68.8

102.2

61.2

81.05

54.5

64.28

48.6

50.97

43.2

40.42

38.5

32.06

30.5

20.16

24.2

12.68

19.2

7.974

15.2

5.015

12.1

3.154

Source: ASTM B8 Specification for Concentric-Lay-Stranded Copper Conductors, Hard, Medium-Hard, or Soft

Technical Information

Conductors

Nominal Overall Diameter

(in.)

0.470 0.419 0.373

0.332 0.292 0.260

0.232 0.206 0.184

0.164 0.146 0.130

0.116 0.0915 0.0726

0.0576 0.0456 0.0363

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Conductors

Stranding, Diameter, Area, DC Resistance and Weight (20 AWG Through 2,000 kcmil)

Table 4?Copper conductor stranding, diameter, area, weight and DC resistance

Number/Diameter

Nominal Area

Size

of Individual Wires

(mm2)

(cmils)

(AWG)

(in.)

(mm)

0.50

987

? 1/0.032 1/0.613

?

1,020

20 7/0.0121 7/0.307

0.75

1,480

? 1/0.036 1/0.991

?

1,620

18 1/0.403 1/1.02

?

1,620

18 7/0.0152 7/0.386

1.0

1,970

? 1/0.045 1/1.14

1.0

1,970

? 7/0.017 7/0.432

?

2,580

16 1/0.0508 1/1.29

?

2,580

16 7/0.0192 7/0.488

1.5

2,960

? 1/0.055 1/1.40

1.5

2,960

? 7/0.021 7/0.533

?

4,110

14 1/0.641 1/1.63

?

4,110

14 7/0.0242 7/0.615

2.5

4,930

? 1/0.071 1/1.80

2.5

4,930

? 7/0.027 7/0.686

?

6,530

12 1/0.0808 1/2.05

?

6,530

12 7/0.0305 7/0.755

4

7,890

? 1/0.089 1/2.26

4

7,890

? 7/0.034 7/0.864

?

10,380

10 1/0.1019 1/2.59

?

10,380

10 7/0.0385 7/0.978

6

11,800

? 1/0.109 1/2.77

6

11,800

? 7/0.042 7/0.107

?

13,090

?

13,090

?

16,510

9 1/0.1144 7/2.91 9 7/0.0432 7/1.10 8 1/0.1285 1/3.26

?

16,510

10

19,700

8 7/0.0486 7/1.23 ? 1/0.141 1/3.58

10

19,700

?

20,820

?

20,820

? 7/0.054 7/1.37 7 1/0.1443 1/3.67 7 7/0.0545 7/1.38

?

26,240

?

26,240

16

31,600

6 1/0.162 1/4.11 6 7/0.0612 7/1.55 ? 7/0.068 7/1.73

?

33,090

?

41,740

25

49,300

6 7/0.0688 7/1.75 4 7/0.0772 7/1.96 ? 7/0.065 7/2.16

?

52,620

35

69,100

35

69,100

3 7/0.0867 7/2.20 ? 7/0.100 7/2.54 ? 19/0.061 19/1.55

Overall

Diameter

Nominal Weight

(in.) (mm) (lb./1,000 ft.) (kg/km)

0.032 0.81 3.100

4.613

0.036 0.91 3.157

4.098

0.039 0.99 4.603

6.851

0.040 1.02 4.917

7.316

0.046 1.16 4.980

7.410

0.045 1.14 6.130

9.122

0.051 1.30 6.293 0.061 1.29 7.810 0.058 1.46 7.877

9.266 11.63 11.82

0.055 1.40 9.157 13.63

0.063 1.60 8.837 14.14

0.064 1.63 12.44

18.51

0.073 1.84 12.62

18.78

0.071 1.80 15.26

22.71

0.081 2.06 15.71

23.38

0.081 2.05 19.76

29.41

0.092 2.32 20.05

29.84

0.089 2.26 23.98

35.68

0.102 2.59 24.91

37.08

0.102 2.59 31.43

46.77

0.116 2.93 31.94

47.54

0.109 2.77 35.97

53.52

0.126 3.21 38.00

56.55

0.1144 2.91 39.60

58.93

0.130 3.30 40.23

59.86

0.128 3.26 50.17

74.36

0.146 3.70 50.90

75.75

0.141 3.58 60.17

89.54

0.162 4.12 62.83

93.51

0.144 3.67 63.03

93.80

0.164 4.15 64.00

95.24

0.162 4.11 79.43 118.2 0.184 4.66 80.73 120.1 0.204 5.18 99.67 148.3

0.206 5.24 102.0

151.8

0.232 5.88 128.4

191.1

0.255 6.48 155.7

231.7

0.260 6.61 162.0

241.1

0.300 7.62 215.5

320.7

0.305 7.75 218.1

324.5

DC Resistance at 20?C (68?F)

(ohms/1,000 ft.) (ohms/km)

10.13

32.33

10.22

33.77

6.820

22.37

6.387

20.95

6.523

21.40

5.127

16.80

5.213

17.11

4.020

13.19

4.087

13.41

3.430

11.25

3.417

11.21

2.524

8.281

2.573

8.442

2.057

6.750

2.067

6.782

1.589

5.212

1.620

5.315

1.309

4.296

1.304

4.277

0.999

3.277

1.017

3.335

0.8730

2.864

0.8543

2.803

0.7923

2.600

0.8073

2.649

0.6147

2.061

0.6380

2.093

0.5217

1.711

0.5167

1.695

0.4980

1.634

0.5073

1.664

0.3950

1.296

0.4023

1.320

0.3259

1.069

0.3183 0.2528 0.2176

1.044 0.8295 0.6843

0.2005 0.1507 0.1495

0.6577 0.4944 0.4909

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