Mining Cable Engineering Handbook

Mining Cable
Engineering Handbook
2nd Edition
Table of Contents
1. GENERAL PROPERTIES OF COPPER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 1
1.1 Resistance to Annealing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 1
1.1.1 Table 1: Solid Wire Breaking Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 1
1.2 Table 2: Properties of Annealed Copper Wire. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 1
1.3 The AWG. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 2
1.3.1 Rules of Thumb for AWG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 2
1.3.2 AWG Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 2
1.3.2.1Table 3: Wire Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 2
2. RESISTANCE AND RESISTIVITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 3
2.1
DC Resistance of Stranded Conductors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 3
2.1.1 Table 4: Factors for Determining DC Resistance of Uncoated and Coated Copper Strand . . . . . . . . . . . . . . . . . . . . . . . Pg. 3
2.1.2 Table 5: Copper Wire DC Resistance @ 20°C (68°F) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 4
2.2
2.2.1 Skin Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 4
AC Resistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 4
2.2.2 Proximity Effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 4
2.3 2.3.1 Table 6: Resistance and Inductance Ratios due to Skin Effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 5
Inter-Strand AC Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 5
3. AMPACITY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 6
3.1 3.1.1 Table 7: Ampacities for Portable Power Cables with 90°C Insulation, Amperes per Conductor . . . . . . . . . . . . . . . . . . . Pg. 6
Method of Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 6
3.1.2 Table 8: Ampacities for Mine Power Feeder Cables with 90°C Insulation, Three Conductor . . . . . . . . . . . . . . . . . . . . . Pg. 7
3.1.3. Table 9: Approximate Ampacity Correction Factors for Cables of all Voltages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 7
3.1.4. Table 10: Allowable Short Circuit Currents for Insulated Copper Conductors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 8
3.2
Warning: Hot Conductors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 9
4. IMPEDANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 10
4.1
Impedance Terms and Calculations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 10
4.2
Reactance Terms and Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 10
4.2.1 Table 11: Resistance and Reactance of Portable Power Cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 11
4.2.2 Table 12: Resistance and Reactance of Mine Power Feeder Cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 11
4.3
4.3.1 Table 13: Approximate Voltage Drop Factors at 90°C and 75°C Conductor Temperatures . . . . . . . . . . . . . . . . . . . . . Pg. 12
4.4
Voltage Regulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 12
4.5
Improving Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 12
Voltage Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 12
5. SHIELDING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 13
5.1
5.1.1 Figure 1: Cable as a Capacitor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 13
Cable as a Capacitor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 13
5.2
5.2.1 Figure 2: Conductor Shielding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 14
5.3
5.3.1 To Eliminate Non-Symmetrical Electrical Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 14
5.3.2 To Provide a Definite Capacitance to Ground for the Insulated Conductor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 15
5.3.3 To Reduce the Hazard of Both Shock and Danger to Life and Property. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 15
Shielding and Stress Relief in Insulated Cable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 14
Functions of Insulation Shielding Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 14
5.4
Insulation Stress Relief (Insulation Shielding). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 15
5.5
Stress-Relief Cones. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 16
5.5.1 Figure 3: Voltage Gradient vs. Distance along Dielectric from Shield. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 16
5.6
5.6.1 Figure 4: Stress Distribution at Edge of the Shielding System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 16
5.7
Stress-Relief Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 17
5.7.1
Figure 5: Conductor Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 17
5.8
Extruded Stress-Relief Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 17
5.9
Applications of Shields. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 17
5.10
Effects of Shield Loss on Ampacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 18
5.11
Dielectric Constant. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 18
5.11.1 Table 14: Shielding Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 19
Concentrated Stresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 16
6. INSULATION AND JACKET STABILITY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 20
6.1
Partial Discharge Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 20
6.2
The Major Prerequisite of Insulated Cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 20
6.3
Ozone Resistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 20
6.4
Jacket — Physical Toughness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 21
6.5
Jacket — Hardness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 21
6.6
Thermal Stability and Heat Resistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 21
6.7
Moisture Penetration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 22
6.7.1 Table 15: Moisture Transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 22
6.8
Sunlight Resistance of Cable Coverings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 22
6.9
ICEA Minimum Requirements for Mining Cable Jackets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 22
6.9.1 Table 16: ICEA Minimum Requirements for CPE and CSPE Jackets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 22
6.9.2 Table 17: ICEA Minimum Requirements for Thermoplastic Polyurethane Jackets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 22
7. FLEXIBILITY AND FLEX LIFE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 23
7.1
Low Temperature Flexibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 23
7.2
Flex Life as a Function of Stress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 23
7.3
Bending Radii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 24
7.3.1 Table 18: Flex Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 24
7.4
ICEA Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 24
8. STANDARD PRODUCT LINE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 25
8.1
Table 19: Product Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 25
8.2
Table 20: Mining Cable Product Constructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 26
8.3
Table 21: Mining Cable Application Guide. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 27
9. TECHNICAL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 28
9.1
Engineering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 28
9.1.1 Table 22: Ampacity Correction Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 28
9.1.2 Table 23: Voltage Drop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 28
9.1.3 Table 24: AWG-to-Metric Conversion Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 28
9.2
Why and How Mining Cables Fail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 29
9.3
Table 25: Unit Conversion Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 30
9.4
Table 26: Temperature Conversion Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pg. 31
The information contained herein is intended for evaluation by technically skilled persons. Any person relying on this document does so at their own independent discretion
and sole risk, assumes all risks and liability whatsoever in connection with such use, and General Cable will have no liability with respect thereto, whether the claim is based
in contract, tort or other legal theory. General Cable makes no representations or warranties, expressed or implied, with respect to the accuracy, completeness or reliability
of this document.
GENERAL PROPERTIES OF COPPER
1.1
Resistance to Annealing
Both hard-drawn and medium-hard tempered wire can
become annealed when used to conduct high current.
Because current heating causes wire to lose tensile
strength, it is imperative that hard-drawn and mediumhard tempers are designed to resist annealing.
Test values of tensile strength and elongation properties
of copper wire are used to determine its final temper.
See 1.1.1 Table 1 for specifics of solid wire breaking
strength.
1.1.1 Table 1: Solid Wire Breaking Strength
Approximate Tensile Strength
HARD-DRAWN1
Size
(AWG)
4/0
3/0
2/0
1/0
1
MEDIUM-HARD2
ANNEALED (SOFT) 3
lbs
kg
lbs
kg
lbs
kg
8143
6720
5519
4518
3688
3693
3048
2503
2049
1672
6980
5666
4599
3731
3024
3166
2570
2086
1692
1371
5983
4744
3763
2985
2432
2713
2151
1706
1354
1103
2
3
4
5
6
3002
2439
1970
1590
1280
1361
1106
893
721
580
2450
1984
1584
1265
1010
1111
899
718
573
458
1928
1529
1213
961
762
874
693
550
436
345
7
8
9
10
11
1030
826
660
529
423
467
374
299
240
191
806
644
513
410
327
365
292
233
186
148
605
479
380
314
249
274
217
172
142
112
12
13
14
15
16
337
268
214
170
135
152
121
97
77
61
262
209
167
133
106
118
94
75
60
48
197
157
124
98
78
89
71
56
44
35
1Hard-Drawn
wire has the highest tensile strength, lowest conductivity and lowest elongation of the tempers. The hot-roll
rod is cold-drawn without annealing, which work-hardens the wire.
2Medium-Hard
requires the hot-roll rod be briefly cold-worked to the desired diameter. The wire is then heated moderately.
The tensile strength, conductivity and elongation properties are mid-way between hard-drawn and annealed.
3Annealed
(Soft) wire is cold-drawn first to the desired diameter, then a high heat is applied to soften the copper.
This temper has the lowest tensile strength, highest conductivity and greatest elongation of the three tempers.
1.2 Table 2: Properties of Annealed Copper Wire
1
1
Atomic Weight
63.57
Atomic Number
29
Density at 20°C
8.89 g/cm³
Melting Point
1083°C - 1981.4°F
Boiling Point
2310°C - 4190°F
Specific Heat, 25°C
0.0918 cal per g per deg C
Latent Heat of Fusion
43.3 g-cal per gram
Linear Coefficient of Expansion
0.00001692 per deg C/0.0000094 per deg F
Electrical Resistivity at 20°C
0.15328 ohm (meter gram)
Temperature Coefficient of Resistivity at 20°C
0.00393 per deg C
Thermal Conductivity
0.93 cal/cm²/cm/sec/deg C
1.3 The AWG
1.3.2AWG Conversions
Copper conductor size conversion is determined by:
Circular mils = sq in. x 1,273,240 = sq mm x 1,973.5
For cross-sectional forms other than circular,
where S is the cross-sectional area in square inches,
the conversions are:
AWG sizes represent the successive steps in the process
of drawing wire. The AWG uses a simple mathematical
law to determine size, and its numbers are retrogressive
to wire size represented.
• Diameters are formed by geometrical progressions
based on two diameter specifications.
•
The basis of the AWG is the diameter of No. 4/0
defined as 0.0046 in. and No. 36 as 0.0050 in. The
38 sizes between these two diameters are specified
by the ratio of any diameter to the diameter of the
next greater number, as shown below:
39
39
0.4600
92
=
0.0050
X = 1.1229322
• The square of the ratio equals 1.26010.
• The sixth power of the ratio equals 2.0050 to the
next greater diameter.
• As the ratio is approximately 2, it applies a number of
useful relations and short cuts in wire computations.
1.3.1 Rules of Thumb for AWG
All rules are approximate.
1.An increase of three gauge numbers doubles the area
and weight and halves the dc resistance.
2.An increase of six gauge numbers doubles the
diameter.
3.An increase of ten gauge numbers
multiplies the area and weight by 10
and divides the resistance by 10.
4.For sizes 4/0 AWG to 29 AWG, the
maximum and minimum diameters
can be found by adding or subtracting
1% of the nominal diameters.
5.For sizes 30 AWG to 46 AWG, the
maximum and minimum diameters
can be found by adding or subtracting
.0001" of the nominal diameters.
6.The weight of 2 AWG copper wire is
very close to 200 lb per 1000 ft.
7. A 10 AWG wire has a diameter
of approximately 0.10 in., an area
of about 10,000 cir mils and a
resistance of approximately 1.0 ohm
per 1000 ft.
0.0081455
S
Feet per ohm at 20°C = 122770 x S
2.1135
Ohms per pound at 20°C = 2 6
S 10
Pounds per ohm at 20°C = 473160 x S2
Pounds per 1000 feet at 20°C = 3854.09 x S
Ohms per 1000 feet at 20°C =
Feet per pound at 20°C =
0.259465
S
Mil is the term used to express wire diameter
measurement and represents a unit of length equal
to 1/1000 of an inch.
Circular mil is used to define cross-sectional areas.
One circular mil equals 0.7854 square mil.
For actual wire conversions, see 1.3.2.1 Table 3.
1.3.2.1 Table 3: Wire Conversions
SIZE
AWG/
kcmil
500
350
300
250
4/0
3/0
2/0
1/0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
cir mils
500000
350000
300000
250000
211600
167800
133100
105600
83690
66360
52620
41740
33090
26240
20820
16510
13090
10380
8230
6530
5180
4110
3260
2580
CROSS-SECTIONAL AREA
sq inch
0.3927
0.2749
0.2356
0.1963
0.1662
0.1318
0.1045
0.0829
0.0657
0.0521
0.0413
0.0328
0.0260
0.0206
0.0164
0.0130
0.0103
0.0082
0.0065
0.0051
0.0041
0.0032
0.0026
0.0020
sq mm
253.4
177.3
152.0
126.7
107.2
85.0
67.4
53.5
42.4
33.6
26.7
21.1
16.8
13.3
10.5
8.4
6.6
5.3
4.2
3.3
2.6
2.1
1.7
1.3
WEIGHT
lb/1000 ft
1513.5
1059.5
908.0
756.6
640.5
507.8
402.8
319.5
253.3
200.9
159.3
126.3
100.2
79.4
63.0
50.0
39.6
31.4
24.9
19.8
15.7
12.4
9.9
7.8
kg/km
2252.1
1576.5
1351.1
1125.8
952.8
755.4
599.2
475.3
376.8
298.9
237.0
187.9
149.1
118.1
93.8
74.4
58.9
46.8
37.0
29.5
23.4
18.4
14.7
11.6
OVERALL DIAMETER
inch
0.707
0.592
0.548
0.500
0.460
0.410
0.365
0.325
0.289
0.258
0.229
0.204
0.182
0.162
0.144
0.128
0.114
0.102
0.091
0.081
0.072
0.064
0.057
0.051
mm
17.96
15.04
13.92
12.70
11.68
10.41
9.27
8.26
7.34
6.50
5.82
5.18
4.62
4.12
3.66
3.25
2.90
2.59
2.31
2.06
1.83
1.63
1.45
1.30
2
RESISTANCE AND RESISTIVITY
It is commonly held that electric current in stranded conductors
is confined to individual strands and does not transfer from
strand to strand parallel to the axis of the conductor. Using this
reasoning, dc resistance is calculated as follows:
2
• Compare the length of each strand to the axial
length of the conductor. Average the increased length
of the strands.
• Multiply the effective cross-sectional area (the first
product) by the average strand length increase to get
the strand resistance.
• Multiply the number of individual strands by the
cross-section area of one wire. This product is the
effective cross-sectional area of the conductor.
2.1 DC Resistance of Stranded Conductors
In accordance with ASTM Specification B189-63,
Tables 4 and 5 show factors for determining the dc
resistance of uncoated and coated copper stranded
conductors.
2.1.1 Table 4: Factors for Determining DC Resistance of Uncoated and Coated Copper Strand
Uncoated
Coated
Diameter of Individual Coated Wires, Inch
All Sizes
0.460-0.290
0.289-0.103
0.102-0.201
0.0200-0.0111
0.0110-0.0030
94.16
93.15
Minimum Conductivity, Percent
100
98
97.66
97.16
96.16
Temperature, Degrees C
Conductor
25
20
25
20
25
20
25
20
25
20
25
20
25
20
Resistance Factors — Ohms per Circular Mil *
CONCENTRIC
To 2000 kcmil
10786 10579 10989
2001 to 3000
10892 10682 11097
3001 to 3400
10998 10786 11205
4001 to 5000
11104 10890 11313
ROPE-LAY — Concentric-Stranded Members
49 Wires
10892 10682 11097
133 Wires
10998 10786 11205
259 Wires
11051 10838 11259
427 Wires
11104 10890 11313
Over 427 Wires 11209 10993 11420
ROPE-LAY — Bunch-Stranded Members
7 Ropes
10998 10786 11205
19, 37, 61 Ropes 11104 10890 11313
7 x 7 Ropes
11209 10993 11420
19 x 7, 37 x 7 or
61 x 7 Ropes
10795
10900
11006
11112
11045
11153
11261
11370
10832
10938
11044
11150
11102
11210
11319
11428
10888
10994
11101
11208
11217
11327
11437
11547
11001
11109
11217
11325
11456
11568
11681
11793
11235
11345
11455
11566
11579
11693
11806
11920
11356
11647
11579
11690
10900
11006
11059
11112
11199
11153
11261
11315
11370
11478
10938
11044
11097
11150
11257
11210
11319
11374
11428
11537
10994
11101
11155
11208
11315
11327
11437
11492
11547
11657
11109
11217
11271
11325
11432
11568
11681
11737
11793
11905
11345
11455
11511
11566
11676
11693
11806
11863
11920
12033
11467
11579
11634
11690
11801
11006
11112
11199
11261
11370
11478
11044
11150
11257
11319
11428
11537
11101
11208
11315
11437
11547
11657
11217
11325
11432
11681
11793
11905
11455
11566
11676
11806
11920
12033
11579
11690
11801
11315
11097
11528
11305
11586
11363
11646
11421
11767
11540
12018
11786
12147
11913
BUNCHED STRAND
All sizes
10786
10579
10989
10795
11045
10832
11102
10888
11217
11001
11456
11235
11579
11356
*The direct current resistance in ohms per 1000 feet of the completed strand shall not exceed the value calculated by dividing the appropriate factor above by the nominal circular mil area of the conductor.
3
2.1.2 Table 5: Copper Wire DC Resistance at 20°C (68°F)
Solid
Conductor
Size
(AWG/kcmil)
ohms
per 1000 ft
ohms
per km
ohms
per 1000 ft
ohms
per km
ohms
per 1000 ft
ohms
per km
ohms
per 1000 ft
ohms
per km
4/0
3/0
2/0
1/0
1
0.0504
0.0636
0.0802
0.1022
0.1289
0.166
0.209
0.263
0.335
0.423
0.0502
0.0633
0.0798
0.1016
0.1282
0.165
0.206
0.262
0.334
0.421
0.0490
0.0618
0.0779
0.0983
0.1239
0.161
0.203
0.256
0.322
0.407
0.0502
0.0633
0.0798
0.1006
0.1275
0.165
0.208
0.262
0.330
0.419
2
3
4
5
6
0.1625
0.2050
0.2584
0.3260
0.4110
0.533
0.672
0.848
1.070
1.350
0.1617
0.2039
0.2571
0.3243
0.4088
0.531
0.669
0.843
1.060
1.340
0.1563
0.1971
0.2485
0.3135
0.3952
0.513
0.647
0.815
1.030
1.300
0.1609
0.2028
0.2557
0.3226
0.4067
0.528
0.667
0.839
1.060
1.330
7
8
9
10
11
0.5180
0.6538
0.8241
1.0390
1.3100
1.700
2.140
2.700
3.410
4.300
0.5153
0.6498
0.8199
1.0330
1.3000
1.690
2.130
2.690
3.390
4.280
0.4981
0.6281
0.7925
0.9988
1.2600
1.630
2.060
2.600
3.280
4.140
0.5126
0.6465
0.8156
1.0390
1.3100
1.680
2.120
2.680
3.410
4.300
12
13
14
15
16
1.6500
2.0800
2.6300
3.3140
4.1800
5.420
6.840
8.940
10.900
13.700
1.6400
2.0700
2.6100
3.2900
4.1600
5.390
6.770
8.580
10.800
13.700
1.5900
2.0000
2.5200
3.1800
4.0200
5.210
6.590
8.270
10.400
13.100
1.6500
2.0800
2.6300
3.3100
4.1800
5.420
6.840
8.640
10.900
13.700
BARE HARD-DRAWN
BARE MEDIUM-HARD
BARE ANNEALED (SOFT)
TINNED ANNEALED (SOFT)
2.2 AC Resistance
For conductors larger than 1,500,000 circular mils,
other calculation formulas must be used for accuracy.
The non-uniform cross-sectional distribution of current
also affects the inductance, the value of which is less
than if the current density were uniform. The table of
skin effect ratios, therefore, lists the inductance ratio
L/L0 where L is the inductance due to a non-uniform
current density and L0 is the inductance assuming
uniform current density.
A conductor offers a greater resistance to the flow of
alternating current than it does to direct current. The
magnitude of the increase is usually expressed as an
“ac/dc ratio”. The reasons for the increase are several:
1) skin effect, 2) proximity effect, 3) hysteresis and
eddy current losses in nearby ferromagnetic materials,
and 4) induced losses in short-circuited nearby
non-ferromagnetic materials.
2.2.1Skin Effect describes the phenomena of alternating
current flowing more densely near the surface of the
conductor. The net effect is a reduction in effective
area and an increase in the resistance. To calculate skin
effect in tubular conductors made of solid wire to an
infinitely thin tube, the curves of Ewan are used.
The parameter is:
X = 0.027678
f
R0
2.2.2Proximity Effect is the distortion of the crosssectional current distribution of the conductor due
to nearby currents. To calculate approximately the
proximity effect, use the following formula:
1-phase fp = 4
GMR
GMD
3-phase fp = 6 GMR
GMD
2
2
R -1
R0
R -1
R0
Where: f = frequency, Hz
R0 = dc resistance at operating temperature,
ohms per 1000 feet
Where: fp = the factor to account for proximity effect
When: f = 60 Hz, the formula becomes:
0.21439
x=
R0
GMD = the geometric mean spacing of the
conductors
Table 6 gives the factors for skin effect ratio R/R0 as a
function of x, where R is the ac resistance and R0 is the
dc resistance.
GMR = the geometric mean radius of the equal
conductors
R/R0 = the skin effect ratio
The resistance of a conductor based on skin- and
proximity-effect is expressed:
R = R0 R + f p
R0
4
2.3 Inter-Strand AC Resistance
The effect of inter-strand resistance is also significant to ac resistance. If the current is, or can be,
confined to the individual strands, skin effect will be materially reduced below that of an effectively
solid conductor. The difference may be 2 percent or more.
2.3.1 Table 6: Resistance and Inductance Ratios due to Skin Effect (when f = 60 Hz)
X
R/R0
L/L0
X
R/R0
L/L0
X
R/R0
L/L0
X
R/R0
L/L0
0.0
0.1
0.2
0.3
0.4
1.00000
1.00000
1.00001
1.00004
1.00013
1.00000
1.00000
1.00000
0.99998
0.99993
2.9
3.0
3.1
3.2
3.3
1.28644
1.31809
1.35102
1.38504
1.41999
0.86012
0.84517
0.82975
0.81397
0.79794
6.6
6.8
7.0
7.2
7.4
2.60313
2.67312
2.74319
2.81334
2.88355
0.42389
0.41171
0.40021
0.38933
0.37902
17.0
18.0
19.0
20.0
21.0
6.26817
6.62129
6.97446
7.32767
7.68091
0.16614
0.15694
0.14870
0.14128
0.13456
0.5
0.6
0.7
0.8
0.9
1.00032
1.00067
1.00124
1.00212
1.00340
0.99984
0.99966
0.99937
0.99894
0.99830
3.4
3.5
3.6
3.7
3.8
1.45570
1.49202
1.52879
1.56587
1.60314
0.78175
0.76550
0.74929
0.73320
0.71729
7.6
7.8
8.0
8.2
8.4
2.95380
3.02411
3.09445
3.16480
3.23518
0.36923
0.35992
0.35107
0.34263
0.33460
22.0
23.0
24.0
25.0
26.0
8.03418
8.38748
8.74079
9.09412
9.44748
0.12846
0.12288
0.11777
0.11307
0.10872
1.0
1.1
1.2
1.3
1.4
1.00519
1.00758
1.01071
1.01470
1.01969
0.99741
0.99621
0.99465
0.99266
0.99017
3.9
4.0
4.1
4.2
4.3
1.64051
1.67787
1.71516
1.75233
1.78933
0.70165
0.68632
0.67135
0.65677
0.64262
8.6
8.8
9.0
9.2
9.4
3.30557
3.37597
3.44638
3.51680
3.58723
0.32692
0.31958
0.31257
0.30585
0.29941
28.0
30.0
32.0
34.0
36.0
10.15422
10.86101
11.56785
12.27471
12.98160
0.10096
0.09424
0.08835
0.08316
0.07854
1.5
1.6
1.7
1.8
1.9
1.02582
1.03323
1.04205
1.05240
1.06440
0.98711
0.98342
0.97904
0.97390
0.96795
4.4
4.5
4.6
4.7
4.8
1.82614
1.86275
1.89914
1.93533
1.97131
0.62890
0.61563
0.60281
0.59044
0.57852
9.6
9.8
10.0
10.5
11.0
3.65766
3.72812
3.79857
3.97477
4.15100
0.29324
0.28731
0.28162
0.26832
0.25622
38.0
40.0
42.0
44.0
46.0
13.68852
14.39545
15.10240
15.80936
16.51634
0.07441
0.07069
0.06733
0.06427
0.06148
2.0
2.1
2.2
2.3
2.4
1.07816
1.09375
1.11126
1.13069
1.15207
0.96113
0.95343
0.94482
0.93527
0.92482
4.9
5.0
5.2
5.4
5.6
2.00710
2.04272
2.11353
2.18389
2.25393
0.56703
0.55597
0.53506
0.51566
0.49764
11.5
12.0
12.5
13.0
13.5
4.32727
4.50358
4.67993
4.85631
5.03272
0.24516
0.23501
0.22567
0.21703
0.20903
48.0
50.0
60.0
70.0
80.0
17.22333
17.93032
21.46541
25.00063
28.53593
0.05892
0.05656
0.04713
0.04040
0.03535
2.5
2.6
2.7
2.8
1.17538
1.20056
1.22753
1.25620
0.91347
0.90126
0.88825
0.87451
5.8
6.0
6.2
6.4
2.32380
2.39359
2.46338
2.53321
0.48086
0.46521
0.45056
0.43682
14.0
14.5
15.0
16.0
5.20915
5.38560
5.56208
5.91509
0.20160
0.19468
0.18822
0.17649
90.0
100.0
—
—
32.07127
35.60666
—
—
0.03142
0.02828
—
—
R/R0 = Resistance ratio due to skin effect
L/L0 = Inductance ratio due to skin effect
X=
0.21439
R0
Reproduced from National Bureau of Standards
5
AMPACITY
3
3.1 Method of Calculations
To calculate ampacity, a two-part relationship is used:
Ampacity (current-carrying capacity) calculation
should take into account natural variables such as solar
warming, wind and air density, viscosity, and thermal
conductivity. Ampacity is a temperature rating; mining
cables insulated with ethylene propylene are rated to
operate continuously at 90°C. Commonly used ICEA
ratings (Publication No. S-75-381/NEMA WC 58) are
for cables isolated in still air of 40°C with a conductor
temperature of 90°C.
I2 Rac = QC – QS
Where: QC = heat dissipated through conduction,
convection and radiation
QS = heat absorbed from solar radiation
T = I2 Rac Rth
Where: Rth = thermal resistance of the insulation
Rac = effective electrical resistance
I = current
T = temperature difference of conductor and
jacket surface
When the two equations are solved simultaneously,
it defines the ampacity for a set of given parameters.
See 3.1.1 and 3.1.2 Tables 7 and 8.
3.1.1 Table 7: Ampacities for Portable Power Cables with 90°C Insulation,
Amperes per Conductor
Single Conductor
Power
Conductor
2001800115001Size
0-2000
8000
15000
25000
(AWG or
Volts
Volts*
Volts*
Volts*
kcmil)
Nonshielded Shielded Shielded Shielded
8
83
—
—
—
6
109
112
—
—
4
145
148
—
—
3
167
171
—
—
2
192
195
195
—
1
223
225
225
222
Two
Conductor
Round
and Flat
0-2000
Volts
72
95
127
145
167
191
Three
Conductor
Round
and Flat
Three Conductor Round
8001150010-8000
15000
25000
0-5000 Volts Volts*
Volts*
Volts*
Nonshielded Shielded Shielded Shielded
59
—
—
—
79
93
—
—
104
122
—
—
120
140
—
—
138
159
164
178
161
184
187
191
Four
Five
Six
Conductor Conductor Conductor
0-2000
Volts
54
72
93
106
122
143
0-2000
Volts
50
68
88
100
116
136
0-2000
Volts
48
64
83
95
110
129
1/0
2/0
3/0
4/0
258
298
345
400
260
299
345
400
259
298
343
397
255
293
337
389
217
250
286
328
186
215
249
287
211
243
279
321
215
246
283
325
218
249
286
327
165
192
221
255
—
—
—
—
—
—
—
—
250
300
350
400
450
500
550
600
650
700
750
800
900
1000
445
500
552
600
650
695
737
780
820
855
898
925
1010
1076
444
496
549
596
640
688
732
779
817
845
889
925
998
1061
440
491
543
590
633
678
—
—
—
—
—
—
—
—
430
480
529
572
615
659
—
—
—
—
—
—
—
—
363
400
436
470
497
524
—
—
—
—
—
—
—
—
320
357
394
430
460
487
—
—
—
—
—
—
—
—
355
398
435
470
503
536
—
—
—
—
—
—
—
—
359
—
—
—
—
—
—
—
—
—
—
—
—
—
360
—
—
—
—
—
—
—
—
—
—
—
—
—
280
310
335
356
377
395
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
*These ampacities are based on single isolated cable in air operated with open-circuited shield.
NOTE — these ampacities are based on a conductor temperature of 90°C and an ambient air temperature of 40°C.
Permission has been granted by ICEA to reproduce this material.
6
3.1.2 Table 8: Ampacities for Mine Power Feeder Cables with 90°C
Insulation, Three Conductor
5000 to 25,000 Volts Copper
Ampacities*
Conductor Size
(AWG or kcmil)
5000 & 8000 Volts
15000 Volts
25000 Volts
6
4
2
1
93
122
159
184
—
125
164
187
—
—
—
189
1/0
2/0
3/0
4/0
211
243
279
321
215
246
283
325
216
247
284
325
250
300
350
400
500
355
398
435
470
536
359
401
438
473
536
359
401
438
473
536
*These ampacities are based on single isolated cable in air operated with open-circuited shield.
NOTE — these ampacities are based on a conductor temperature of 90°C and an ambient air temperature of 40°C.
Permission has been granted by ICEA to reproduce this material.
3.1.3 Table 9: Approximate Ampacity Correction Factors for
Cables of all Voltages
Correction factors are listed below for various ambient temperatures.
Ambient Temperature
Correction Factors for Insulations Rated At:
°C
90°C
75°C
10
20
30
40
50
1.26
1.18
1.10
1.00
0.90
1.36
1.25
1.13
1.00
0.85
When cables are used with one or more layers wound on a reel, the ampacities should be derated as follows:
No. of Layers
Multiply Ampacities By:
1
2
3
4
0.85
0.65
0.45
0.35
Permission has been granted by ICEA to reproduce this material.
7
3.1.4 Table 10: Allowable Short Circuit Currents for Insulated Copper Conductors
Allowable Short Circuit Currents for Insulated Copper Conductors
Rated for 90°C Continuous Operation
1000000
100000
Short Circuit Current—Amperes
10000
Curves Based on the Formula
1000
2
[ ] t = 0.0297 log [ TT ++ 234
234 ]
I
A
2
10
1
I =Short Circuit Current–Amperes
A =Conductor Area–Circular Mils
t =Time of Short Circuit–Seconds
T1=Maximum Operating Temperature–90°C
T2=Maximum Short Circuit Temperature–250°C
100
10
8
6
4
2
1 1/0 2/0 3/0 4/0250
350
500
750 1000
Conductor Size (AWG/kcmil)
1 Cycles
16 Cycles
2 Cycles
30 Cycles
4 Cycles
60 Cycles
8 Cycles
100 Cycles
Reprinted with permission from ICEA P-32-382 Short Circuit characteristics of Insulated Conductors,
Copyright 2006, Insulated Cable Engineers Association, Carrollton, GA 30112. This reprint is not the
referenced subject, which is represented only by the standard in its entirety.
8
3.2 Warning: Hot Conductors
9
A primary goal in the development of rubber or
plastic compounds for cable insulations and jackets is
to obtain physical and electrical characteristics that
are stable at elevated temperatures in either wet or
dry environments. From an engineering and design
viewpoint, high temperature resistance is highly
desirable and increases the safety factor during periods
of emergency. Insulation stability during an emergency
overload is of extreme importance. As noted in ICEA
Standards covering emergency overload ratings,
“Operation at these emergency overload temperatures
shall not exceed 100 hrs. per year. Such 100-hr.
overload periods shall not exceed five over the life of
the cable.”
Operating temperatures must be kept in the correct,
and safe, perspective. As the current load increases,
the following phenomena occur:
• Conductor resistance increases
• Voltage drop increases and causes conductor
inefficiency
• Increased conductor temperature becomes an
electric furnace
• Degradation of insulations and coverings is
accelerated
IMPEDANCE
4.1 Impedance Terms and Calculations
4
4.2 Reactance Terms and Calculations
Impedance (Z) of a circuit to a specified periodic
current, and potential difference, is the ratio of effective
value of the potential difference between terminals to
the effective value of the current, there being no source
of power in the portion of circuit under consideration,
is expressed:
Z = E (ohms) or
I
Z=
2
R +X
2
Reactance of a portion of a circuit for a sinusoidal
current, and potential difference of the same frequency,
is the product of the sine of the angular phase
difference between the current and potential difference
times the ratio of the effective potential difference to
the effective current, when there is no source of power
in the portion of the circuit under consideration.
Inductive Reactance (XL) is calculated from the
relationship:
(ohms)
Admittance (Y) is the reciprocal of impedance.
Ohm’s Law applies to all metallic circuits and to others
containing electrolytic resistance. It states that current
in a circuit is directly proportional to the electromotive
force in the circuit. In a direct-current circuit:
Where: L = inductance (henries)
I = E = Electromotive Force (volts) (amperes)
R
Resistance (ohms)
f = frequency (Hertz)
Also from the above formula:
XL = 0.05292 log10 GMR (ohms to neutral per
GMD
1000 feet at 60 Hz)
In an alternating current circuit:
XL = 2f L (ohms)
For other frequencies, multiply X L by:
Reff = Rdc x Rac /Rdc
f
60
Capacitive Reactance (XC) is calculated from:
Where: Rac /Rdc = ratio of alternating-current
resistance to direct-current resistance
of the circuit conductor
XC = –
1 (ohms)
2fC
Where: C = capacitance (farads)
For resistance and reactance of portable power and
feeder cables, see 4.1.1 and 4.1.2 Tables 11 and 12.
Total Reactance (X) of a circuit is the sum of the
inductive and capacitive reactance:
X = 2fL + -
1
= XL + XC
2fC
• If there is no capacitance in the circuit, the total
reactance is equal to the inductive reactance.
• If there is no inductance in the circuit, the total
reactance is equal to the capacitance reactance.
10
4.2.1 Table 11: Resistance and Reactance of Portable Power Cables
Conductor Size
(AWG or kcmil)
8
7
6
5
4
3
2
1
1/0
2/0
3/0
4/0
250
300
350
400
500
600
700
800
900
1000
R[ac]1
Ohms/1000 Ft.
XL [60HZ] 2
Ohms/1000 Ft.
75°C
90°C
.838
.665
.528
.418
.332
.263
.209
.165
.128
.102
.081
.065
.055
.046
.039
.035
.028
.023
.020
.018
.016
.014
.878
.696
.552
.438
.347
.275
.218
.173
.134
.107
.085
.068
.057
.048
.041
.036
.029
.024
.021
.019
.017
.015
2 kV3
G-GC,
G + GC
.034
.033
.032
.031
.031
.031
.029
.0303
.029
.029
.028
.027
.0283
.027
.027
.027
.026
.026
.026
.025
.025
.025
2 kV3
SHD-GC
5 kV
SHD-GC
8 kV
SHD-GC
15 kV
SHD-GC
25 kV
SHD-GC
—
—
.038
.036
.035
.034
.033
.033
.032
.031
.030
.029
.0303
.029
.029
.028
.028
.027
.027
.026
.026
.026
—
—
.043
.042
.040
.039
.038
.036
.035
.034
.033
.032
.031
.031
.030
.030
.029
.028
.028
.028
.027
.027
—
—
—
—
.043
.042
.040
.039
.037
.036
.035
.034
.033
.032
.032
.031
.030
.030
.029
.029
.028
.028
—
—
—
—
—
—
.044
.042
.040
.039
.038
.036
.036
.035
.034
.033
.032
.032
.031
.030
.030
.030
—
—
—
—
—
—
—
.046
.044
.043
.041
.040
.039
.038
.037
.036
.035
.034
.033
.033
.032
.032
1 a.Sizes
8 AWG - 1 AWG based on tinned copper 94.16% conductivity.
b.Sizes 1/0 AWG and larger based on tinned copper 96.16% conductivity.
c.Resistance increased per ASTM B-172, Note 7, to compensate for stranding factor.
d.Skin effect calculated according to Arnold’s Table, National Bureau of Standards.
e.Nominal cross-sectional areas.
2 a.Based
on conductor dimensions given for Class H Rope Lay conductors in ICEA S-75-381/NEMA WC 58.
b.Extruded strand thickness .015".
c.Insulation thickness according to nominals given in ICEA S-75-381/NEMA WC 58.
3 a.Deviations
from normal progression due to changes in insulation thickness for same voltage rating.
4.2.2 Table 12: Resistance and Reactance of Mine Power Feeder Cables
Conductor Size
(AWG or kcmil)
6
5
4
3
2
1
1/0
2/0
3/0
4/0
250
300
350
400
500
600
700
800
900
1000
R[ac]1
Ohms/1000 Ft.
90°C
.510
.404
.321
.254
.201
.160
.127
.101
.080
.063
.054
.045
.039
.034
.027
.023
.020
.017
.016
.014
XL [60HZ] 2
Ohms/1000 Ft.
5 kV
MP-GC
.041
.040
.038
.037
.036
.035
.034
.033
.032
.031
.030
.029
.029
.029
.028
.028
.027
.027
.027
.026
8 kV
MP-GC
.044
.042
.041
.039
.038
.037
.035
.034
.033
.032
.031
.031
.030
.030
.029
.029
.028
.028
.027
.027
15 kV
MP-GC
—
—
—
—
.042
.041
.039
.038
.036
.035
.034
.034
.033
.032
.031
.031
.030
.030
.029
.029
1 a.Based
on bare copper 100% conductivity.
b.Nominal cross-sectional areas.
c.Resistance increased by increments per ASTM B-8 to compensate for stranding factor.
d.Skin effect calculated according to Arnold’s Table, National Bureau of Standards.
2 a.Based
on conductor dimensions given for Class B Concentric Stranded conductors in ICEA S-75-381/NEMA WC 58.
b.Extruded strand shield thickness .015".
c.Insulation thickness according to nominals given in ICEA S-75-381/NEMA WC 58.
11
25 kV
MP-GC
—
—
—
—
—
.044
.043
.042
.040
.039
.038
.037
.036
.035
.034
.033
.032
.031
.031
—
4.3 Voltage Drop
Load current, power factor and impedance of
the conductor all affect voltage drop. Generally,
capacitance can be neglected in distribution circuits
because its effect on voltage drop is negligible for the
circuit lengths and operating voltages used. A major
point in circuit design is to determine the proper size
of conductor that will carry the current load without
exceeding a specified voltage drop.
In a balanced 3-phase circuit, the drop in phase voltage
is 1.73 times the drop in each conductor when they are
treated as a single-phase circuit with no return wire.
V drop = 1.73 IZ cos ( – )
Where: I = amperes in each conductor
Z= ohmic impedance of one conductor
= impedance angle
= power factor angle
See 4.2.1 Table 13.
4.3.1 Table 13: Approximate Voltage Drop Factors at 90°C and 75°C
Conductor Temperatures
Three Conductor Cables at 90°C Conductor Temperature
60 Hertz Phase-To-Phase Voltage Drop Per Ampere Per 1000 ft at Power Factors of:
Conductor Size
80%
90%
(AWG/kcmil)
6
0.82
0.90
4
0.54
0.58
2
0.35
0.38
1
0.29
0.31
1/0
0.24
0.25
2/0
0.20
0.20
3/0
0.16
0.17
4/0
0.14
0.14
250
0.12
0.12
300
0.11
0.11
350
0.10
0.09
400
0.09
0.08
500
0.08
0.07
Three Conductor Cables at 75°C Conductor Temperature
60 Hertz Phase-To-Phase Voltage Drop Per Ampere Per 1000 ft at Power Factors of:
Conductor Size
80%
90%
(AWG/kcmil)
6
0.76
0.83
4
0.50
0.54
2
0.33
0.35
1
0.27
0.28
1/0
0.22
0.23
2/0
0.18
0.19
3/0
0.15
0.15
4/0
0.13
0.13
250
0.11
0.11
300
0.10
0.09
350
0.09
0.08
400
0.08
0.08
500
0.07
0.06
4.4 Voltage Regulation
Where: VR = voltage regulation in percent
Es = sending-end voltage to neutral in volts
Er = receiving-end voltage to neutral in volts
The permissible variation in voltage depends to a
considerable extent on the kind of service being
supplied. It must be kept within practical limits in order
0.95
0.60
0.38
0.30
0.24
0.19
0.15
0.12
0.10
0.08
0.07
0.06
0.05
100%
0.85
0.55
0.35
0.28
0.22
0.17
0.14
0.11
0.09
0.08
0.07
0.06
0.05
to obtain proper candle power and life from lamps and
proper efficiency, torque, power factor, etc., from motor
loads. Voltage regulation may usually be kept within
desirable limits normally not over 5 percent by insuring
low resistance and reactance of the lines and feeders. If
this is impractical, special apparatus must be installed
to regulate voltage.
Voltage regulations are expressed as follows:
E -E
VR = s r x 100, percent
Er
The relationship between Es and Er is expressed by:
Es = Er + IrZ (vectorially)
Es = as above
Er = as above
Ir = receiving-end current per conductor, amperes
Z = total series impedance per conductor, ohms
100%
The National Electrical Code (NEC) recommends
maximum voltage drops of 3% for power loads and 1%
for lighting loads.
4.5 Improving Voltage Regulation
•
•
•
•
Use a larger conductor size
Reduce conductor spacing
Paralleling circuits
Improve power factor
12
SHIELDING 5
5.1 Cable as a Capacitor
A capacitor is an electrical device consisting of two
conducting surfaces separated by insulating material
(dielectric) such as air, paper, oil or rubber. A shielded
cable operates as a capacitor with the insulation as
the dielectric and the shield as the other conducting
surface. This must be taken into consideration during
cable design and application.
5.1.1 Figure 1: Cable as a Capacitor
Jacket
Shield
Air
Insulation
Cable
The following characteristics of a capacitor are related
to shielded cable:
• A capacitor stores electrical energy. The SIC
(specific inductive capacity) of insulation is
determined by comparing the amount of energy an
insulated cable (capacitor) can store to the amount
of energy stored by a capacitor using air
(in a vacuum) as the insulator.
For example, if a certain air capacitor has a
measured capacitance of one F (microfarad), but
the measured capacitance is 3 F when the air is
replaced with insulation, then the insulating material
has a SIC of about 3. SIC is also referred to as
dielectric constant and permittivity. For a capacitor
designed to store energy, a high SIC is desirable.
For a cable that transports electricity, a low SIC is
needed. For 600 Volt cables, the SIC is generally kept
below 7. For 15kV cable, the SIC should be below 4.
Cable above 15kV should have the SIC value kept as
low as possible.
13
Copper Plate
Copper Plate
Capacitator
• A capacitor permits the flow of alternating current.
The amount of ac flow is dependent on the SIC of
the insulation and the frequency of the current. In
cable design, ac flow should be kept in mind when
determining whether or not to shield, the type of
grounding method, the cable size, the conductor
spacing and the geometry of cable.
5.2 Shielding and Stress Relief in
Insulated Cable
Shielding systems work to confine the dielectric field to
the insulation. Without proper shielding, the electrical
stress can cause deterioration of the insulation and
danger of electrical shock.
There are three principal functions of a shielding
system:
5.3.1To Eliminate Non-Symmetrical
Electrical Stresses
CONDUCTOR SHIELDING
Conductor stress relief (conductor shielding) functions
to eliminate stress between the conductor and the
insulation. To be effective, the conducting layer must
adhere to, or remain in intimate contact with, the
insulation. 5.2.1 Figure 2A shows an air gap between
the conductor and the insulation. The voltage stress
across the air gap can cause ionization of the air and
result in deterioration of the insulation. 5.2.1 Figure 2B
shows extruded shielding around the conductor. This
layer presents a smooth round electrode (precluding
excessive gradients due to physical irregularities) that
has the same electrical potential as the conductor and
is bonded to the insulation so there is no ionization
within the cable.
5.3 Functions of Insulation Shielding
Systems
5.2.1 Figure 2: Conductor Shielding
Power cables are subjected to radial tangential or
longitudinal voltage stresses. Radial stresses are always
present in cable insulation when the cable is energized.
Insulation is most efficient when the electrical field is
uniformly distributed around the conductor and within
the envelope of the cable insulation. Non-uniform
distribution of the dielectric field results in increased
radial stress in portions of the insulation and less
efficient usage of the insulation as a whole.
Shielding systems applied over the insulation of the
individual conductors remove the fillers from the
dielectric field, leaving a symmetrically distributed
radial stress. This utilizes the insulation to its greatest
efficiency and in the direction of its greatest strength.
AIR VOID
A
CONDUCTOR SHIELD
B
One of the basic laws of electric fields states that
voltage applied across dielectrics in series will divide
in inverse proportion to the dielectric constant on the
material. Thus, when an air gap is in series with the
cable insulation, a portion of the voltage will appear
across the gap. The surface of the insulation or cable
will then have a voltage to ground equal to the voltage
across the gap. This voltage can approach the full
conductor potential when the air gap is large and
will approach ground potential when the surface is in
contact with a grounded surface. This phenomenon
gives rise to tangential and longitudinal stresses.
Tangential stresses are always associated with nonuniform radial stress. They occur in multi-conductor
cables when the individual conductors are not shielded
and in all single conductor non-shielded cables installed
so that non-symmetrical relations exist between
conductor and adjacent grounded surfaces.
Longitudinal stresses are not necessarily associated
with non-uniform radial stress but are always apparent
with radial stresses of different magnitude along the
length of the cable. These stresses occur in non-shielded
cable installed so that intermittent contacts or variable
spacings exist between the cable surface and grounded
objects. Examples include metal conduits, steel
supports or cable brackets, local conducting areas and
wet spots in ducts.
The proper application of an external shielding system
will eliminate tangential and longitudinal stresses by
bringing the entire surface to ground potential.
14
5.3.2To Provide a Definite Capacitance to
Ground for the Insulated Conductor
cable, a considerable potential difference may exist
between the covering and the ground. This may create
a hazard for the following reasons:
Cables which are laid in ducts or directly in the earth
will often run through sections of dry and wet soil or
ducts having varying electrical characteristics. This
results in varying electrostatic capacity to ground,
hence a change in the surge impedance of the cable. In
addition, cables entering metallic ducts or risers will
have a change in impedance due to varying capacitance
to ground.
In cables connected to overhead lines, traveling waves
caused by lightning or induction from charged clouds
or fog drifts will be partially reflected at points of
change in the surge impedance. This will result in
further build-up of the surge voltage in the cable,
which may cause breakdown of the insulation. In
some cases where cables run through very dry ground,
traveling waves may be induced by direct induction
from the clouds.
a. Contact with the covering may induce panic or fear,
resulting in hazards to life such as falls, or other
secondary factors, even though the electrical shock
may not be lethal.
b. Contact with the covering under unusual conditions
may be a hazard to life by electrical shock if the
charging current from a considerable length of cable
is carried by the covering to the point of contact.
This might occur, for instance, with a heavily
contaminated damp cable surface.
c. The potential difference may cause sparking, which
could result in the ignition of explosive gas mixtures
in tunnels or duct systems.
A properly grounded shielding system will confine the
dielectric field to the insulation and eliminate these
hazards. To obtain full benefit, the shield should be
applied over the insulation of individual conductors.
An additional safety factor is derived from shielding by
providing a path to ground; this reduces the hazard to
workmen who may accidently drive a pick or other tool
into the energized conductor of the cable.
See 5.11.1 Table 14 for different types of shielding
systems.
The application of a shielding system over the
insulation of individual conductors or the assembly of
a multi-conductor cable reduces these surge potentials.
A shield over the insulation of individual conductors
functions by:
a. creating a uniform capacitance from conductor to
ground, resulting in a uniform surge impedance
along the cable, thus preventing partial reflections
and the consequent build-up of the surge voltages
within the cable.
b. providing maximum capacitance from conductor to
ground, thereby effecting the maximum reduction of
the incoming surge potential.
5.4 Insulation Stress Relief
(Insulation Shielding)
Shielding systems consist of a semi-conducting layer or
an extruded layer of electrically conducting material
over the insulation in conjunction with a metallic,
non-magnetic tape, wire, or braid. The stress-relief
portion (inner layer) of the system must adhere to the
insulation under all conditions. It and the metallic
portion serve as a current-carrying medium for charging
and leakage currents.
The shielding system should operate at or near ground
potential at all times. Shielding which does not have
adequate ground connection is more hazardous from a
safety standpoint than non-shielded cable. An undergrounded or “floating” shield can cause electrical
failure of the cable, and if the potential on such a shield
penetrates the outer jacket, the resultant discharge can
result in an extreme shock hazard. To minimize the
possibility of open sections in the shielding system, use
a trailing cable design that has the grounding conductor
laid in intimate contact with the insulation shielding
throughout the length of the cable.
c. absorbing surge energy in the same manner as
the conductor by reason of the current induced
magnetically in the shield.
d. reducing stress on the insulation under many
circuit arrangements, because surge potential will
momentarily exist on both conductors and shield.
A shielding system applied over the multi-conductor
cable assembly is somewhat less effective with respect
to points (a) and (c). Although it does not provide
the maximum capacitance (b), it is an improvement
upon non-shielded, non-metallic-covered cables and is
probably equal to individual shield for (d).
5.3.3To Reduce the Hazard of Both Shock
and Danger to Life and Property
15
As explained in 5.3.2, when the outer surface of the
insulation or covering of insulated cables is not in
contact with ground throughout the entire length of the
A stress-relief cone is important in relieving the area
of concentrated stress at the end of a grounded shield.
This stress occurs because of the potential difference
between the surface of the insulation without shielding
and the surface, which is still shielded.
A stress-relief cone relieves the stress, but it does not
eliminate it. Even a well-designed stress cone has areas
of stress concentration, but the conditions will be
tolerable.
The shielding system must be removed completely
and proper stress-relief cones made at all shield
terminations. If all elements of the shield are not
removed, excessive leakage current, tracking and
flashover may result.
When determining the removal distance of grounded
external shielding, remember that the voltage gradient
between the end of the conductor and the shield
terminus is extremely non-linear. The longitudinal and
radial stress concentration at the edge of the shield
diminishes only slightly as the axial length of shielding
system removal is increased. 5.5.1 Figure 3 clearly
illustrates that the voltage gradient at the shield edge is
the same (for graphing purposes) for three terminations
with different removal distances.
5.6 Concentrated Stresses
The voltage gradient between the end of the conductor
and the edge of the shielding system is non-linear and,
for all practical purposes, independent of removal
distance. One of the primary purposes of shielding in
cables is to achieve uniform radial stress distribution
so that all flux lines extend from the conductor to the
grounded metallic shield.
5.6.1 Figure 4 shows the stress distribution at the
edge of the shielding. For the portion of the conductor
beyond the edge of the shield, the shielding tape is
still the nearest component at ground potential, and
all electrical flux lines concentrate at this shield edge.
Under such conditions, this is the weakest point
in the cable circuit and electrical failure can result
either radially or longitudinally at this location unless
measures are taken to reduce these electrical stresses.
5.5.1 Figure 3: Voltage Gradient vs.
Distance along Dielectric from Shield
100
VOLTAGE
IN PERCENT
5.5 Stress-Relief Cones
0
DISTANCE ALONG
DIELECTRIC
FROM SHIELD
5.6.1 Figure 4: Stress Distribution at Edge
of the Shielding System
INSULATION
CONDUCTOR
FLUX LINES
SHIELDING SYSTEM
16
5.7 Stress-Relief Mechanism
5.7.1 Figure 5: Conductor Stresses
5.7.1 Figure 5 illustrates a conventional stressrelief cone made of hand-applied insulating tapes
and shielding braid. This simple mechanism
relieves the high concentration of stress at the
cable shield terminus by providing a gradual
transition. The cone does not completely
eliminate the stress but reduces it below the limits
of trouble-free cable operation.
FLUX LINES
CABLE SHIELDING
SYSTEM
CONDUCTOR
INSULATION
HAND-APPLIED INSULATING TAPES
HAND-APPLIED SHIELDING BRAID
5.8 Extruded Stress-Relief Layer
Following
are some factors that characterize
both types:
The use of conducting extruded layer as part of the
shielding system has gained acceptance through three
contributing factors:
Thermoplastic Conducting Compounds
• Deforms at elevated temperatures
• Sharp increase in resistance at higher temperatures
1. Cable Acceptance
• Not inherently flame resistant
Extruded conducting compounds used over the
insulation have proved to have distinct advantages
over tape bedding. Conducting compounds are not
susceptible to the deterioration of fabric tapes and
are not limited to the decreased physical protection
of tape. Conducting compounds have also had an
excellent performance record over a wide range of
cable environments and locations.
• Does not subject insulation to vulcanization or
cross-linking
• Adhesion control is possible for easy stripping
• Good performance record in a variety of applications
Thermosetting Conducting Compounds
• Excellent deformation characteristics
• Consistent in resistant characteristics over
temperature range
2. Rigorous Requirements for Corona Levels
Corona level testing determines voids in conductor/
insulation interface and insulation surface/shielding
system interface. Because fabric tapes have a wide
range of limitations in conductivity, splices, fiber
ends, uneven tensions and tape laps, there is a
difficulty in obtaining a consistent, smooth interface
which reduces voids. Conducting compounds suffer
from none of these variables and have proven to be
far less likely to develop voids.
3. Intimate Contact With Insulation Surface
Conducting insulation shield or extruded stress-relief
layers provide smooth round electrodes and intimate
contact with the insulation. It is able to match the
expansion characteristics of the insulation, which
prevents the formation of voids.
Extruded conducting compounds are available in
thermoplastic and thermosetting types. The choice is
dependent on cable type, thermal rating, emergency
and short-circuit ratings.
17
• Not inherently flame resistant
• Requires heat for cross-linking, can cause conductor
drift and very tight bond with insulation
5.9 Applications of Shields
Association of Edison Illuminating Companies (AEIC)
and Insulated Cable Engineers Association (ICEA)
offer shielding guidelines and recommendations.
It may be difficult to determine when a shield is
absolutely required, but a properly installed shielded
cable will always offer the maximum in safety and
reliability. The shielding system must always operate
at or near ground potential.
5.10 Effects of Shield Loss on Ampacity
The purpose of a cable insulation shield is to confine
electrostatic stresses to a definite pattern and provide
a fixed path of grounding for cable charging and
leakage currents. When a cable carries current, there is
an electrostatic and a magnetic field. The cable shield
confines the electrostatic field but not the magnetic field.
The magnetic field affects the current density in adjacent
conductors and induces voltage in nearby metallic
objects. If metallic circuits in the cable, or metal nearby,
form a closed electrical path, there will be I 2R losses.
The losses that occur in these “external” circuits are felt
in the electrical characteristics of the cable, particularly
if the object is made of magnetic material which will
increase power loss by hysteresis effects.
Three single conductor cables laid in an equilateral
triangular configuration will experience losses based
on this formula:
S
Xm = 52.92 Log
r
Where: Xm = micro-ohms per foot of cable
S = spacing between centers of cables
in inches
r = radius of cable shield in inches
The Dielectric Constant of a material is defined as the
ratio of the amount of energy that a given capacitor
with insulating material between its plates can store to
the amount of energy that the same capacitor can store
when it has air between its plates. In the cable industry,
the Dielectric Constant of a material is referred to as
Specific Inductive Capacity (SIC).
If one plate of a capacitor is bent into a circle and the
other plate is stretched and then wrapped concentrically
around the first, it is a capacitor and the cross-section of
a shielded cable. Obviously, whenever a shielded cable is
made, a capacitor is also made.
In the case of a shielded, single conductor cable, the size
of this capacitor is:
If cable shields are grounded at both ends, the electrical
circuit is complete, and a current flows as a result of VS.
The power loss due to this current is:
Xm2
Ws = I2Rs
Rs2/ Xm2
Where:
Inductive losses make the use of large single conductor
leaded or armored cables impractical. The low
resistance of these coverings causes excessive losses
that reflect back to the conductor as an increase in
impedance. This results in an excessive voltage drop in
the cable circuit.
7.354Le
C=
Where:
C = picofarads
L = length of cable in feet
e = SIC of insulation
D = outside diameter of insulation
d = inside diameter of insulation
Log (D/d)
Whenever an ac voltage is applied across a capacitor, a
current will flow. In a power cable, this is referred to as
the charging current. The magnitude of this current per
thousand feet of cable is:
I=
2,772.46(kV)e
1,000,000Log (D/d)
Where: I = amperes
kV = kilovolts between conductor and shield
e = SIC of insulation
D = outside diameter of insulation
d = inside diameter of insulation
Ws = micro-watts per foot per cable
Rs = shield resistance in micro-ohms per foot
I = current in conductor, amperes
Xm = micro-ohms per foot of cable
On a three-phase system, the total shield loss is
approximately three times the above value.
Vs = IXm
Where: Vs = micro-volts per foot, to neutral
I = current in conductor, amperes
Xm = micro-ohms per foot of cable
One advantage of a three conductor cable is the
120-degree phase difference between the conductor
currents, which results in a partial cancellation of
the magnetic field around the three conductor cable.
This reduces the losses in the shield to a tolerable level.
The impedance of a three conductor cable is less than
the impedance of three single conductor cables of a
corresponding size.
5.11 Dielectric Constant
If the cable shields are open circuited (i.e., they are
grounded at only one place and they are not in contact
with each other at any one point), the voltage induced in
one of them is:
There are two sources of current in the shield of a cable:
1) the current that is due to the inductive coupling
with the conductor and is a function of the conductor
current, and 2) the current which results from the
capacitive coupling between the conductor and the
shield, which is dependent upon the voltage that exists
between the conductor and the shield.
The current flowing in the shield and the shield
resistance losses show up as heat, similar to losses and
heat due to current in the phase conductor.
18
The ampacity of a cable is dependent on the amount of
heat generated in a cable and the dissipation rate of the
heat to the cable surroundings. Once the surroundings
have been chosen, the amount of heat dissipation is
fixed, as is the amount that the cable can be allowed
to generate. Any heat that the shield generates must be
subtracted from the amount that would otherwise be
allotted to the phase conductor. This reduces ampacity.
The greater the shield losses, the higher the economic
loss. In essence, excessive shield loss translates into
paying a premium to obtain less cable capacity.
5.11.1 Table 14: Shielding Systems
Solid Dielectric Cables
Shielding System
19
Advantages
Disadvantages
Non-Magnetic Copper Tape
Shield
(1) Effective electrostatic shield
(2)Consistent and controlled
electrical properties
(3)Universally accepted – reliable
standard for comparison
(1) Difficult to apply tapes without
wrinkling
(2)Requires semi-con bedding
layer to insure intimate contact
and high corona resistance
(3)Vulnerable to damage during
installation
(4)Relatively high cost
(5)Cutting of tapes during
splicing and termination
requires considerable skill and
careful handling
Semi-Conducting Extruded
Layer With Concentric Metallic
Drain
(1) Effective electrostatic shield
(2)Combination of semi-con layer
with drain wires insures both
intimate contact with insulation
and controllable electrical
properties
(3)Easy to add capacity with
extra or larger wires
(1) Requires caution during
installation to prevent
displacement of wires
(2)Should not be used in contact
with oil
(3)External wires vulnerable to
corrosion
(4)Design balance to control
shield losses critical for top
efficiency in three-phase
operation
Flexible Nylon/Copper Braid
Over Semi-Conducting Tape
(1) Effective electrostatic shield
(2)Provides additional grounding
conductor capacity in type
SHD cables
(3)Good shock hazard protection
(1) Extensive flexing lowers
corona extinction levels
(2)Shield losses relatively high
Flexible Full Copper Braid Over
Semi-Conducting Tape
(1) Effective electrostatic shield
(2) Provides additional grounding
conductor capacity in type
SHD cables
(3) Good shock hazard protection
(1) Extensive flexing lowers corona
extinction levels
(2) Shield losses higher than
nylon/copper
(3) Broken shield wires buttonhook, producing possible
insulation penetration
INSULATION AND JACKET STABILITY
6.1 Partial Discharge Resistance
Partial discharge is the name given to the corona
phenomenon by power cable engineers. Corona, or
partial discharge, is a very complicated phenomenon
and not easily defined. Below are a few accepted facts
that outline the characteristics of partial discharge:
• Ozone resistance is not synonymous with partial
discharge resistance; they are separate phenomena.
• Extinction level is the voltage point where partial
discharge disappears.
• Voids within the insulation, between insulation and
the conductor shield, or between insulation and the
insulation shield can cause partial discharges.
• Extruded strand shields with smooth surfaces and a
bond to the insulation will virtually eliminate partial
discharge at the interface.
• Keeping insulation voids to a minimum will
drastically reduce partial discharge.
• Choose insulation with a high degree of resistance to
partial discharge.
• Design the cable to incorporate features that facilitate
the partial discharge extinction level.
• Use processing techniques that minimize voids.
An insulated cable has one purpose – to transmit
power. To achieve this at the highest possible levels,
the characteristics of the insulated cable must remain
stable and predictable. The environments that affect
performance levels can be divided into four areas:
• Physical environment affects cable installation and
its actual operation. Severe bending, compression,
cutting abrasion, and excessive tension can all
contribute to damage which reduces the reliability of
a cable installation.
• Chemical environment affects the cable components.
Chemical environments such as free chlorine, oil,
ozone, etc., can influence the choice of materials for
insulations and jackets.
• Thermal environment can affect the degradation
of insulation and jackets at elevated levels since the
speed of a chemical reaction is doubled with a 10°C
rise in temperature.
• Electrical environment that causes magnetic and
static fields can result in data logging control cable
interference.
The environments should be taken into consideration
whenever specifying material and cable design.
Thought-out choices allow a balance between economy
and sound engineering.
Similar to an oxygen molecule (O2) in chemical
structure but containing one more atom of oxygen
(O3), ozone is a gas with a pungent characteristic odor.
Ozone can be produced anywhere a combination of
air and an electrical discharge is present and is usually
encountered in diluted form mixed with air.
Cable problems related to ozone are most likely to
occur at voltages above 5kV; however, 2kV cables can
also be attacked if they are in an environment where
ozone is being generated. Ozone and cable coverings
share an interesting history. The chemical nature of
ozone is such that it is capable of deteriorating virtually
every extruded type of cable covering used in the
industry. For many years, the most practical method
of obtaining some degree of ozone resistance in cable
insulation was to incorporate a substantial quantity
of polymerized oil or factice into the compound. The
disadvantage of obtaining ozone resistance in this
fashion is a significant sacrifice of heat aging resistance,
low-temperature flexibility and physical strength.
Ozone attack of cable covering is more easily
understood if the basic polymer is considered as
a discrete and identifiable chemical. The major
component in polymers is a chain of carbon atoms.
How these carbon atoms are linked is the determining
factor in predicting ozone resistance.
6.2 The Major Prerequisite of Insulated
Cables
6.3 Ozone Resistance
• Intimate contact between the outer surface of the
insulation and the shielding system will reduce
partial discharges.
A few factors can minimize partial discharge. Consider
these when specifying insulated cable:
6
20
In some polymers like polyethylene and the ethylenepropylene types, the carbon-to-carbon link or bond in
the main chain looks something like the following:
This arrangement provides excellent ozone resistance.
Many polymers like SBR, Neoprene and natural rubber
have a carbon-to-carbon linkage or bond that looks
like this:
(-C-C = C-C-)
Notice there is a double bond between two of the
carbons. This is the location where ozone attacks and
reacts, splitting the carbon chain and resulting in radial
cracks in the cable covering. The more of these double
bonds present, the more quickly the deterioration in the
presence of ozone, limiting polymers of this type to 600
Volt service.
EPR and XLPE are the leaders in medium-voltage
insulations with inherent or built-in ozone resistance.
EPR and XLPE contain a limited number of double
bonds, virtually all of which are used up in the
vulcanizing process. The resulting compound has a
high degree of ozone resistance without sacrificing
important properties.
The hardness of the cable jacket can be indicative of the
health of the insulation and jacket. Hardness is usually
measured with a Shore Durometer; for example, a
mining-grade synthetic rubber jacket in good condition
would show a Shore A hardness of 65-75. If the jacket
goes to 90, it’s a good indication that it has been
exposed to elevated temperatures and is becoming
brittle.
Elevated temperatures or a loss of plasticizer increase
hardness, while a decrease in hardness signals cable
deterioration. An excessive hardness increase or
decrease is a sign that a problem is occurring.
(-C-C-C-C-)
6.5 Jacket — Hardness
General Cable’s Technology Center monitors polymer
innovations and the development of built-in ozone
resistance. Some of the better ozone-resistant jackets
on the market include CSPE and CPE.
6.6 Thermal Stability and Heat Resistance
Heat resistance is a major component of thermal
stability, cable longevity and reliability. By reviewing
the properties of insulation that affect heat resistance, it
is easier to make cable specifications that will offer true
thermal stability and facilitate service life predictions.
• Heat aging is tested by exposing insulation to
air oven, oxygen bomb and air pressure heat test
(APHT). Noting whether a material gets brittle
or softens during these tests gives good insight to
polymer choice and compounding ingredient control.
• Deformation of the insulation under stress or high
loads should not occur to an excessive degree. In
general, thermoplastic insulations deform more
readily than thermosetting compounds at high
temperatures. At temperatures over 100°C, even
thermosetting compounds will show differing
degrees of deformation. The polymer insulation that
shows the least deformation should be considered the
most stable.
• Creep is the dimensional change of a material under
load over a given time. In vertical riser cable and
terminations, creep could be a very serious problem.
Insulation with zero creep is considered to be
extremely stable.
• Thermal expansion is the fractional change in length
or volume of a material related to a unit change
in temperature. Cables used for alternating heavy
and light current loads will be subject to expansion
and contraction. If the expansion is excessive, the
integrity of the overall design can be disrupted,
and cable failure is accelerated. Thermal expansion
stability is measured by cyclic aging tests.
• Physical properties of insulation, such as tensile
strength and cut resistance, can be reduced
dramatically by repeated exposure to elevated
temperatures. The insulating compound that
retains the greatest degree of its properties after
high temperature aging should be considered the
most stable.
6.4 Jacket — Physical Toughness
For most industrial power cables, the durability of
protective sheaths or jackets is secondary to electrical
stability but still an important part of a cable system.
However, for mining cables, the jacket durability is
more important than electrical stability. Over 90%
of cable failure can be traced to physical damage to
the cable in handling, installation or service. Cable is
laboratory- and field-tested for the following factors of
physical toughness:
• Compression-cut is the result of a crushing load that
ruptures the insulation and/or jacket. The conductor
can act as a cutting tool.
• Impact damage occurs upon impingement. The
degree of damage is dependent upon the foot-pounds
of force and the size of the area impinged.
• Tearing is caused in cables that are pulled over rough
terrain having sharp rocks or other obstructions.
• Abrasion is rare in industrial power cables but occurs
readily in mining applications.
• Deformation is caused by excessive shearing stress
and will be accelerated by high temperatures. Cable
used in fill with large rocks is subject to the natural
shearing stress of the earth’s movements.
21
• Electrical EP rubber properties are also affected
by high temperatures. However, most insulations
are designed to remain stable through a variety of
temperatures.
6.8 Sunlight Resistance of Cable
Coverings
The continuous exposure of cable to weather is a
major concern for cable engineers. All polymer-type
coverings undergo degradation over time. Environment,
installation and chemical composition of the polymer
significantly influence longevity.
Sunlight is a serious and potent threat to wire covering.
The ultraviolet band of sunlight promotes the oxidation
of polymers and results in cracking, chalking and
crazing. Cable coverings that incorporate 2-3% channel
black dispersed in the polymer have proven to provide
the best protection against sunlight deterioration.
6.7 Moisture Penetration
Cables absorb water at a rate determined by the
ambient water temperature, conductor temperature,
cable insulation temperature, and the permeabilities
of the cable jacket and insulation. The usual method
for determining moisture resistance properties is a
gravimetric measurement of the moisture absorbed by
an insulation after seven days in hot water. The value is
reported in mg/in2.
While gravimetric measurements show the amount
of moisture absorbed, there is only one factor
when determining the correct insulation for wet
environments. Some insulations, such as EPR, will
show a high moisture gain but actually have a higher
probability of wet environment survival when voltage
is applied.
Measurements of the maximum flow rate into unloaded
15kV cables in various water temperatures are shown
below:
6.7.1 Table 15: Moisture Transmission
Milligrams Per Foot Per Day
Insulation
PE
XLPE
EPR
50°C
75°C
90°C
3
6
11
10
14
25
42
63
110
The best insulation in a wet environment is the one that
demonstrates intrinsic resistance to moisture-induced
deterioration, as does EPR insulation in the Electrical
Moisture Absorption test. In this test, insulated
conductors are immersed in a 90°C water bath with
continuous voltage stress applied. The cables are tested
until dielectric breakdown occurs. In this test, which
more closely resembles actual field service, EPR outlasts
polyethylenes by a wide margin.
6.9 ICEA Minimum Requirements for
Mining Cable Jackets
6.9.1 Table 16: ICEA Minimum Requirements
for CPE and CSPE Jackets
Physical Requirements
Tensile Strength, lbs. per
square inch
(The pull stress required to
break a specimen)
Elongation, percent
(The percentage increase in
length of a material stressed
in tension before rupture)
Tensile Stress @ 200%, psi
(The tensile force needed to
stretch a material to 200% of
its original length)
Tear Resistance, lbs/in
(The force required to initiate
a tear in a material under
specified conditions)
Heavy-Duty
Extra-HeavyDuty
1,800
2,400
300
300
500
700
N/A
40
6.9.2 Table 17: ICEA Minimum Requirements
for Thermoplastic Polyurethane
Jackets
Physical Requirements
Tensile Strength, lbs. per
square inch
(The pull stress required to
break a specimen)
Elongation, percent
(The percentage increase in
length of a material stressed
in tension before rupture)
Tensile Stress @ 200%, psi
(The tensile force needed to
stretch a material to 200% of
its original length)
Tear Resistance, lbs/in
(The force required to initiate
a tear in a material under
specified conditions)
TPU
3,700
400
800
80
22
FLEXIBILITY AND FLEX LIFE
Cable flexibility is a relative term; there are no real
standards of comparison. In the past, cable coverings
were manufactured from natural rubber (a material
that is inherently flexible) and had to be specially
processed to achieve rigidity. Today, cable coverings
are made of polymer compounds that are by nature
semi-rigid. This major difference in cable-covering
technology has led to new ways to judge cable
flexibility — but the best guide is still personal
judgment and choice.
The flexibility of the copper wires is often offset by
the flexibility of the cable insulation and jacket. Even
reducing the size of individual wires may not mean
the cable becomes more flexible, especially if the
cable covering is harder to bend than the wires it is
protecting.
The primary advantage of a flexible cable is its ease
in handling. Rarely is cable faulted because it is too
flexible, so the judgment becomes how flexible does
it need to be? By taking the following advantages of
flexibility into consideration, you should be able to
weigh that against your rigidity needs to make a sound
judgment.
The more flexible the cable:
• the easier to handle during reeling and the less likely
to sustain damage
• the easier to train into position, which subsequently
saves space
• the easier for craftsmen to work with, which leads to
timesaving and safe working practices
23
7
7.1 Low Temperature Flexibility
All polymers have a tendency to become progressively
stiffer as they are cooled. Cable difficulty occurs when
two conditions are reached:
• Cable coverings become too stiff to be functional.
• Cable coverings become brittle or will shatter under
impact.
The ability of a cable to withstand impact at a low
temperature is a prime factor to consider during
application or installation in northern areas. A cable
which can be bent successfully under a low temperature
may shatter under impact at a significantly higher
temperature.
In general, XLPE, EPR, and CPE all have excellent
low-temperature resistance properties rated to -50°F.
General purpose CSPE and PVC compounds have
passed cold bend tests in the -22°F to -40°F range.
The overall choice for a range of temperature
applications is CPE. In laboratory tests, it showed
superiority in respect to physical properties at elevated,
room and sub-zero temperatures.
7.2 Flex Life as a Function of Stress
The elastic limit of soft copper is safely figured at
10% of its breaking strength. The magnitude of stress
applied to copper above the elastic limit decreases its
flex life at an exponential rate. This is the basis for
manufacturers’ recommendations that portable cables
not be subjected to tensile stresses above this limit.
7.3 Bending Radii
7.4 ICEA Recommendations
Cables are exposed to both electrical and physical
environments. In a physical environment, a cable can
be considered a machine and amenable to the laws
of mechanics. The laws of torsion, shear, tension
and compression forces can all be applied to cable
technology and bending radius.
Mining cable conductors are composed of many wires.
The number of wires in an AWG size is dependent on
the ultimate application and is usually designated as
Class A, B, C, G, H, K, etc. Note that the nearer the
end of the alphabet, the greater the number of wires.
The recommended bending radius for a specific cable
construction is related to, and dependent upon, the
length of lay of individual components making up
the construction. Maximum efficiency in a conductor
composed of a number of wires is obtained only when
all of these wires work together during bending, flexing
or tension.
ICEA minimum recommended bending radii are
standardized at a level to assure that working cable will
not exceed a critical level, resulting in a non-uniform
distribution of individual wire stress.
In the following chart, flex life data is shown for a 4
AWG conductor utilizing one bending radius less than
the critical diameter (A) and one safely above (B).
The ICEA minimum bending radius recommendations
for portable cable are:
• Braid-shielded portable cables — 8 times the cable
diameter
• Non-shielded portable cables — 6 times the cable
diameter
• Flat non-shielded cables — 6 times the minor
dimension
• Copper tape shielded cables — 12 times the cable
diameter
7.3.1 Table 18: Flex Life
No. of Strands
2" Sheave
7
37
133
259
420
1064
203
726
3055
6118
13820
20925
4" Sheave
415
2008
13844
47987
187237
500778
Ratio [A/B]
.489
.362
.221
.127
.074
.042
Notice that even though the ratio of A to B decreases as
the number of strands increases, the flex life increases
significantly with the number of strands.
24
STANDARD PRODUCT LINE
8
8.1 Table 19: Product Matrix
Type
Type
Type
Type
Type
Type
Type
Type
Type
Type
Type
Product Range
Portable Cables
Anaconda® Brand
Lead-Cured Mining-Grade
Cable Types
Carol® Brand
CV-Cured Industrial-Grade
Cable Types
W Flat
G Flat
G-GC Flat
SHD Flat
W Round
G Round
G-GC Round
G plus GC
SHD-GC
SHD plus GC
SHD-PCG Longwall
2kV
2kV
2kV
2kV
2kV
—
2kV
2 & 5kV
2, 5, 8, 15 & 25kV
2 & 5kV
2 & 5kV
—
—
—
—
2kV
2kV
2kV
—
—
—
—
Mine Power Feeder
Type MP-GC (XLPE/PVC)
Type MP-GC (EPR/CPE)
25
8 & 15kV
5, 8, 15 & 25kV
—
—
8.2 Table 20: Mining Cable Product Constructions
General Cable offers the broadest line of mining- and industrial-grade flexible power cables.
Carol®
Brand
IndustrialGrade
Cables
Construction
Anaconda®
Brand
Mining-Grade
Cables
Conductors:
• Fully Annealed Bare Copper
• Fully Annealed Tinned Copper
X
X
Type MP-GC:
• Fully Annealed Bare Copper
X
Insulation:
• Premium-Grade EPR
X
Type MP-GC:
• Premium-Grade EPR
• Premium-Grade XLPE
X
X
X
Shielding:
Type SHD-GC and SHD Plus GC:
• Copper/Textile Braid
X
Type MP-GC:
• EIS/Copper Tape
X
Features and Benefits
Bare Copper Conductor
• Flexible conductor for industrial and static applications
• Cost-effective conductor designs where cable is not being
subjected to repetitive movement
Tinned Copper Conductor
• Enhanced flex life and increased resistance to wire breakage
during repeated movement
• Additional corrosion resistance adds to service life
EPR Insulation
• Outstanding dielectric properties
• Long life at temperatures rated from -40˚C to +90˚C
• Excellent moisture and corona resistance
• Flexible for ease of handling
Tinned Copper/Textile Composite Braid Shielding
• Provides maximum shield flex life
Copper Tape Shielding (EIS)
• 100% coverage and added corona protection
(EIS - Extruded Insulation Shield)
Grounding Conductors:
Type G:
• Covered Bare Copper
• Covered Tinned Copper
X
X (Flat)
Bare Copper Grounding Conductor
• Flexible conductor for industrial applications
• Cost-effective conductor designs where cable is not being
subjected to repetitive movement
Type G-GC:
• Covered Bare Copper
• Covered Tinned Copper
• Tinned Copper
X
X (Flat)
X
Tinned Copper Grounding Conductor
• Enhanced flex life and increased resistance to wire breakage
during repeated movement
• Additional corrosion resistance adds to service life
Type W:
• Covered Bare Copper
• Covered Tinned Copper
X
X
Type SHD-GC:
• Tinned Copper
X
Type MP-GC:
• Tinned Copper
X
Ground-Check Conductors:
• Insulated Bare Copper
• Insulated Tinned Copper
X
Ground-Check Conductor
X (Round) • Provides maximum reliability of the ground-check circuit in
all round constructions
X (Flat)
• Insulated with high-strength polypropylene (Anaconda)
Jackets:
Round Constructions:
• CV-Cured, Single-Layer, Reinforced X
Chlorinated Polyethylene (CPE)
• Lead-Cured, Two-Layer, Reinforced Chlorinated Polyethylene (CPE)
Heavy-Duty, Single-Layer Jacket
• Heavy-duty construction for non-critical applications and
distribution cable
• Good physical characteristics with high degree of resistance
X (Round) to cutting, abrasion and medium-duty flexing
• Excellent general purpose industrial performance
Flat Constructions:
• Lead-Cured, Chlorinated
Polyethylene (CPE)
X (Flat)
Type MP-GC:
• Premium-Grade PVC
• Lead-Cured, Chlorinated
Polyethylene (CPE)
X
X
Extra-Heavy-Duty, Two-Layer Reinforced Jacket
• Increased jacket tensile strength
• Increased mechanical strength for high flex applications
• Maximum mechanical protection against crushing and tearing
• Maximum abrasion resistance
• Preferred construction for mining machines
*Anaconda® Brand Flat and Type MP-GC cables have an extra-heavy-duty, single-layer jacket.
26
8.3 Table 21: Mining Cable Application Guide
APPLICATION
CAROL® BRAND
INDUSTRIAL GRADE
CABLES
ANACONDA®
BRAND
MINING-GRADE
CABLES
UNDERGROUND MINING APPLICATIONS
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Longwall Shearers
Shuttle Cars
Bridge Conveyors
High-Voltage Distribution
Cutting Machines
Loading Machines
Continuous Miners
Drills
Roof Bolters
Locomotives
Hydraulic Pumps
Sectionalized Portable Power
Borehole Cables
Pumps
Accessory Equipment
Two-Conductor Welding
Belt Drives
Hydraulic Power Packs
Belt Take-Ups
Battery Changers
Conveyor Feeder/Breakers
SURFACE MINING APPLICATIONS
Drills
Stripping Shovels
Loading Shovels
Drag Lines
Pumps
Accessory Equipment
General Cable mining cables are manufactured in accordance with:
• ICEA S-75-381 Portable and Power Feeder Cables for Use in Mines and Similar Applications.
• CAN/CSA-C22.2 No. 96 Portable Power Cables, and certified by Natural Resources Canada.
• CAN/CSA-C22.2 No 96.1 Mine Power Feeder Cables.
• Mine Safety and Health Administration flame test requirements and accepted for listing by MSHA.
27
TECHNICAL
9
9.1.2 Table 23: Voltage Drop
9.1 Engineering Information
Working Tension
The maximum working tension per conductor should
not exceed 10 percent of the rated conductor strength.
To determine the approximate tensile strength of the
cable, multiply the total power conductor area (in2) by
30,000 psi.
Bending Radius
The recommended Insulated Cable Engineers
Association (ICEA) minimum bending radii are as
follows:
• Braid-shielded portable cables — 8 times the cable
diameter
• Non-shielded portable cables — 6 times the cable
diameter
• Flat non-shielded cables — 6 times the minor
dimension
• Copper tape shielded cables — 12 times the cable
diameter
9.1.1 Table 22: Ampacity Correction Factors
Approximate for all cable voltages
Correction factors are listed below for various ambiant temperatures.
AMBIENT
TEMPERATURE
CORRECTION FACTORS FOR
INSULATIONS RATED AT:
˚C
10
20
30
40
50
90˚C
1.26
1.18
1.10
1.00
0.90
When cables are used with one or more layers wound on a reel,
the ampacities should be derated as follows:
NUMBER OF LAYERS
MULTIPLY AMPACITIES BY
1
2
3
4
0.85
0.65
0.45
0.35
Approximate for all cable voltages—
Three Conductor Cables
90˚C
60-CYCLE PHASE-TO-PHASE VOLTAGE DROP PER AMPERE
PER 1,000 FT AT POWER FACTORS OF:
SIZE
(AWG or kcmil)
80%
90%
100%
6
4
2
1
1/0
2/0
3/0
4/0
250
300
350
400
500
0.82
0.54
0.35
0.29
0.24
0.20
0.16
0.14
0.12
0.11
0.10
0.09
0.08
0.90
0.58
0.38
0.31
0.25
0.20
0.17
0.14
0.12
0.11
0.09
0.08
0.07
0.95
0.60
0.38
0.30
0.24
0.19
0.15
0.12
0.10
0.08
0.07
0.06
0.05
9.1.3 Table 24: AWG-to-Metric
Conversion Chart
SIZE
(AWG)
18
16
14
12
10
9
8
6
4
2
1
mm2
SIZE
(AWG or
kcmil)
mm2
0.82
1.31
2.08
3.31
5.26
6.63
8.37
13.30
21.15
33.62
42.40
1/0
2/0
3/0
4/0
250
300
350
500
600
750
1000
53.5
64.4
85.0
107.2
126.7
152.0
177.3
253.4
304.0
380.0
506.7
28
9.2 Why and How Mining Cables Fail
Cable breakdowns are neither mysterious nor
unaccountable and almost without exception can be
traced to one or more of the following causes:
1.Excessive tension
2.Mechanical damage
3.Current overload
4.Improper splicing and termination techniques
Excessive Tension
Many cable failures are the direct result of excessive
tension. A cable that has been “stretched” no longer has
the balanced construction that is so vital to long life.
Tension on the conductors subjects the individual wires
in the strand to compression and shear. These thin
wires are damaged and will break more easily when
bent or flexed.
Tension also elongates the conductor insulation. The
elongated insulation is then vulnerable to compression
cutting. It will rupture more easily when it is crushed
against the stranded conductor during runovers. The
insulation will also have a tendency to creep over the
conductor at a splice.
Jackets under tension lose a considerable part of their
resistance to mechanical damage. A jacket under
tension is much more likely to be cut or torn. Stretching
also causes the copper conductors to take a permanent
set. Of course, the insulation and jacket are stretched as
well, but they will return to their original length when
the tension is removed. This difference in the properties
of rubber and copper when subjected to tension will
cause the conductors to be wavy and fail prematurely.
Current Overload
The temperatures of the conductors, insulation
and jacket are, of course, elevated when cables are
subjected to an electrical load. The resistance of
the copper is increased, voltage drop in the cable is
increased, and therefore, a reduced voltage is supplied
to the machine. As a result, the machine calls for
more current, which adds further to cable heating. A
trailing cable’s insulation and jacket materials exhibit
maximum resistance to physical abuse at the rated
conductor temperature of 90°C or less. The ability of
these components to withstand damage decreases as
the temperature increases. Conditions which normally
cause few cable failures suddenly become a problem.
At elevated temperatures, the jacket has lost much of
its resistance to cutting, crushing, tearing and abrasion.
The section of the cable that remains on the reel is most
likely to be damaged by electrical overload. Layering
on the reel hinders ventilation and heat dissipation.
Continued exposure to elevated temperatures will
age the jacket, making it hard and brittle and causing
crazing or cracking upon subsequent reeling.
Improper Splicing and Termination Techniques
Over the years, much work has been done to improve
both splicing materials and techniques.
The following items have been found to be primarily
responsible for unsatisfactory splice service:
To reduce tension on the cable:
1.Avoid backspooling, if possible.
2.If backspooling is unavoidable, locate the tie point as
far back from the haulageway as possible.
3.Tram slowly when passing the tie point.
4.Set hydraulic tension on the cable reel so that
approximately 12-15 feet of cable is picked up off the
mine bottom when starting to tram.
Mechanical Damage
This is one of the most prevalent sources of trailing
cable failures. Factors initiating mechanical damage
include cutting, compression (crushing), punctures and
abrasion. In extreme cases of mechanical damage, the
failure is instant, and the cause can be assigned on the
spot. Many times, however, the cable components are
merely “injured” and become latent failures. At that
point, it may be more difficult to pinpoint the exact
cause and to take remedial action.
29
1.Ending up with a grounding or ground-check
conductor which is shorter than the power
conductors.
2.Semi-conducting residue on the insulation surface
was not removed.
3.Gaps, voids or soft spots in insulating tape build-up.
4.Improper termination of shielding system, leaving
inward-pointing projections.
5.Damage to factory insulation by improper removal of
shielding systems.
6. Excessive slack in one or more individual conductors.
7. Splice has low tensile strength and is easily pulled in
two.
8.Individual wires are damaged during application of
connector.
9.Splice is too bulky — will not pass through cable
guides or over sheaves.
10.Improper application of the outer covering, allowing
water to enter the cable interior.
By choosing a cable with an adequate current rating,
avoiding excessive tension and mechanical damage, and
using proper splicing techniques, it is not unreasonable
to reduce cable-related downtime by 50 percent or
more. This will, of course, translate into increased
production and profits.
9.3 Table 25: Unit Conversion Table
UNIT CONVERSION FACTORS
UNIT
X CONSTANT
= UNIT
UNIT
X CONSTANT
= UNIT
BTU
778.0
foot-pound (ft-lb)
gallons
3.785332
liters (l)
BTU
1054.8
joules
gallons
0.13368
cubic foot (ft3)
BTU
0.293
watt-hours (w-hr)
gallons
231.0
cubic inch (in3)
centimeters (cm)
0.032808
feet (ft)
gallons
3785.332
cubic centimeter (cm3)
centimeters (cm)
0.3937
inches (in)
grams (g)
15.432
grains
centimeters (cm)
0.00001
kilometers (km)
gram/centimeter3 (g/cm3)
0.0361275
pounds/in3 (lb/in3)
centimeters (cm)
0.010
meters (m)
horsepower (hp)
33000.0
ft-lb/min
centimeters (cm)
10.0
millimeters (mm)
horsepower (hp)
550.0
ft-lb/sec
circular mils
0.00064516
circular millimeters
horsepower (hp)
745.7
watts (w)
circular mils
0.0000007854
inches (in )
inch (in)
0.027178
yards (yd)
circular mils
0.00050671
square millimeters (mm2)
inch (in)
0.083333
feet (ft)
0.7854
mils2
inch (in)
0.00002540
kilometer (km)
meter (m)
circular mils
2
2
cubic centimeter (cm )
0.000035314
cubic foot (ft )
inch (in)
0.025400
cubic centimeter (cm3)
0.061023
cubic inch (in3)
inch (in)
2.54000514
centimeter (cm)
cubic centimeter (cm3)
0.000001
cubic meter (m3)
inch (in)
25.4000514
millimeter (mm)
cubic centimeter (cm3)
0.0026417
gallons
inch (in)
1000.0
mils
cubic foot (ft3)
1728.0
cubic inch (in3)
joules
0.000948
BTU
cubic foot (ft3)
28317.016
cubic centimeter (cm3)
joules
107
ergs
cubic inch (in )
0.00057870
cubic feet (ft )
liters (l)
61.0250
cubic inch (in3)
cubic inch (in3)
0.000016387
cubic meter (m3)
meters (m)
1.093611
yards (yd)
feet (ft)
3
3
3
3
cubic inch (in )
16.387162
cubic centimeter (cm )
meters (m)
3.2808333
cubic meter (m3)
1000000.0
centimeter (cm)
meters (m)
39.37
inch (in)
cubic meter (m3)
35.314456
cubic foot (ft3)
meters (m)
100.0
centimeter (cm)
cubic meter (m3)
264.17
gallons
miles
1760.0
yards (yd)
feet (ft)
0.00018939
miles
miles
5280.0
feet (ft)
feet (ft)
0.33333
yards (yd)
miles
1.6093
kilometer (km)
feet (ft)
12
inches (in)
millimeters (mm)
0.0032808
feet (ft)
feet (ft)
0.00030480
kilometers (km)
millimeters (mm)
0.03937
inch (in)
feet (ft)
0.30480
meters (m)
millimeters (mm)
0.001
meters (m)
feet (ft)
30.480
centimeters (cm)
millimeters (mm)
0.01
centimeters (cm)
feet (ft)
304.80
millimeters (mm)
millimeters (mm)
39.3701
mils
feet/pound (ft/lb)
0.00067197
meters/grams (m/g)
millimeters (mm)
1000.0
microns (u)
foot-pound (ft-lb)
0.001285
BTU
watts (w)
44.25
ft-lb/minute
foot-pound (ft-lb)
1.356
joules
watts (w)
0.737562
ft-lb/sec
foot-pound (ft-lb)
0.1383
kilogram/meter (kg/m)
watts (w)
0.001341
horsepower (hp)
3
3
30
9.4 Table 26: Temperature Conversion Chart
To use this chart, find your known temperature (˚F or ˚C) in the shaded column. If the known temperature
is in ˚C and you wish to know its value in ˚F, move to the adjacent right-hand column. If the known
temperature is in ˚F and you wish to know its value in ˚C, move to the adjacent left-hand column.
°C
KNOWN
TEMP
°F
°C
KNOWN
TEMP
°F
°C
KNOWN
TEMP
°F
°C
KNOWN
TEMP
°F
°C
KNOWN
TEMP
Temperature Conversion Formulas
°F
-45.0 -49.0 -56.2 -17.2
1.0
33.8 10.6
51.0 123.8 38.3 101.0 213.8 66.1 151.0 303.8
-44.4 -48.0 -54.4 -16.7
2.0
35.6 11.1
52.0 125.6 38.9 102.0 215.6 66.7 152.0 305.6
-43.9 -47.0 -52.6 -16.1
3.0
37.4 11.7
53.0 127.4 39.4 103.0 217.4 67.2 153.0 307.4
-43.3 -46.0 -50.8 -15.6
4.0
39.2 12.2
54.0 129.2 40.0 104.0 219.2 67.8 154.0 309.2
-42.8 -45.0 -49.0 -15.0
5.0
41.0 12.8
55.0 131.0 40.6 105.0 221.0 68.3 155.0 311.0
-42.2 -44.0 -47.2 -14.4
6.0
42.8 13.3
56.0 132.8 41.1 106.0 222.8 68.9 156.0 312.8
-41.7 -43.0 -45.4 -13.9
7.0
44.6 13.9
57.0 134.6 41.7 107.0 224.6 69.4 157.0 314.6
-41.1 -42.0 -43.6 -13.3
8.0
46.4 14.4
58.0 136.4 42.2 108.0 226.4 70.0 158.0 316.4
-40.6 -41.0 -41.8 -12.8
9.0
48.2 15.0
59.0 138.2 42.8 109.0 228.2 70.6 159.0 318.2
-40.0 -40.0 -40.0 -12.2 10.0
50.0 15.6
60.0 140.0 43.3 110.0 230.0 71.1 160.0 320.0
-39.4 -39.0 -38.2 -11.7 11.0
51.8 16.1
61.0 141.8 43.9 111.0 231.8 71.7 161.0 321.8
-38.9 -38.0 -36.4 -11.1 12.0
53.6 16.7
62.0 143.6 44.4 112.0 233.6 72.2 162.0 323.6
-38.3 -37.0 -34.6 -10.6 13.0
55.4 17.2
63.0 145.4 45.0 113.0 235.4 72.8 163.0 325.4
-37.8 -36.0 -32.8 -10.0 14.0
57.2 17.8
64.0 147.2 45.6 114.0 237.2 73.3 164.0 327.2
-37.2 -35.0 -31.0
-9.4 15.0
59.0 18.3
65.0 149.0 46.1 115.0 239.0 73.9 165.0 329.0
-36.7 -34.0 -29.2
-8.9 16.0
60.8 18.9
66.0 150.8 46.7 116.0 240.8 74.4 166.0 330.8
-36.1 -33.0 -27.4
-8.3
17.0
62.6 19.4
67.0 152.6 47.2 117.0 242.6 75.0 167.0 332.6
-35.6 -32.0 -25.6
-7.8 18.0
64.4 20.0
68.0 154.4 47.8 118.0 244.4 75.6 168.0 334.4
-35.0 -31.0 -23.8
-7.2 19.0
66.2 20.6
69.0 156.2 48.3 119.0 246.2 76.1 169.0 336.2
-34.4 -30.0 -22.0
-6.7 20.0
68.0 21.1
70.0 158.0 48.9 120.0 248.0 76.7 170.0 338.0
-33.9 -29.0 -20.2
-6.1 21.0
69.8 21.7
71.0 159.8 49.4 121.0 249.8 77.2 171.0 339.8
-33.3 -28.0 -18.4
-5.6 22.0
71.6 22.2
72.0 161.6 50.0 122.0 251.6 77.8 172.0 341.6
73.0 163.4 50.6 123.0 253.4 78.3 173.0 343.4
-32.8 -27.0 -16.6
-5.0 23.0
73.4 22.8
-32.2 -26.0 -14.8
-4.4 24.0
75.2 23.3
74.0 165.2 51.1 124.0 255.2 78.9 174.0 345.2
-31.7 -25.0 -13.0
-3.9 25.0
77.0 23.9
75.0 167.0 51.7 125.0 257.0 79.4 175.0 347.0
76.0 168.8 52.2 126.0 258.8 80.0 176.0 348.8
-31.1 -24.0 -11.2
-3.3 26.0
78.8 24.4
-30.6 -23.0
-9.4
-2.8 27.0
80.6 25.0
77.0 170.6 52.8 127.0 260.6 80.6 177.0 350.6
-30.0 -22.0
-7.6
-2.2 28.0
82.4 25.6
78.0 172.4 53.3 128.0 262.4 81.1 178.0 352.4
-29.4 -21.0
-5.8
-1.7 29.0
84.2 26.1
79.0 174.2 53.9 129.0 264.2 81.7 179.0 354.2
-28.9 -20.0
-4.0
-1.1 30.0
86.0 26.7
80.0 176.0 54.4 130.0 266.0 82.2 180.0 356.0
-28.3 -19.0
-2.2
-0.6 31.0
87.8 27.2
81.0 177.8 55.0 131.0 256.8 82.8 181.0 357.8
-27.8 -18.0
-0.4
0.0 32.0
89.6 27.8
82.0 179.6 55.6 132.0 269.6 83.3 182.0 359.6
-27.2 -17.0
1.4
0.6 33.0
91.4 28.3
83.0 181.4 56.1 133.0 271.4 83.9 183.0 361.4
-26.7 -16.0
3.2
1.1 34.0
93.2 28.9
84.0 183.2 56.7 134.0 273.2 84.4 184.0 363.2
-26.1 -15.0
5.0
1.7 35.0
95.0 29.4
85.0 185.0 57.2 135.0 275.0 85.0 185.0 365.0
-25.6 -14.0
6.8
2.2 36.0
96.8 30.0
86.0 186.8 57.8 136.0 276.8 85.6 186.0 366.8
-25.0 -13.0
8.6
2.8 37.0
98.6 30.6
87.0 188.6 58.3 137.0 278.6 86.1 187.0 368.6
-24.4 -12.0
10.4
3.3 38.0 100.4 31.1
88.0 190.4 58.9 138.0 280.4 86.7 188.0 370.4
-23.9 -11.0
12.2
3.9 39.0 102.2 31.7
89.0 192.2 59.4 139.0 282.2 87.2 189.0 372.2
-23.3 -10.0
14.0
4.4 40.0 104.0 32.2
90.0 194.0 60.0 140.0 284.0 87.8 190.0 374.0
-22.8
-9.0
15.8
5.0 41.0 105.8 32.8
91.0 195.8 60.6 141.0 285.8 88.3 191.0 375.8
-22.2
-8.0
17.6
5.6 42.0 107.6 33.3
92.0 197.6 61.1 142.0 287.6 88.9 192.0 377.6
-21.7
-7.0
19.4
6.1 43.0 109.4 33.9
93.0 199.4 61.7 143.0 289.4 89.4 193.0 379.4
-21.1
-6.0
21.2
6.7 44.0 111.2 34.4
94.0 201.2 62.2 144.0 291.2 90.0 194.0 381.2
-20.6
-5.0
23.0
7.2 45.0 113.0 35.0
95.0 203.0 62.8 145.0 293.0 90.6 195.0 383.0
-20.0
-4.0
24.8
7.8 46.0 114.8 35.6
96.0 204.8 63.3 146.0 294.8 91.1 196.0 384.8
-19.4
-3.0
26.6
8.3 47.0 116.6 36.1
97.0 206.6 63.9 147.0 296.6 91.7 197.0 386.6
-18.9
-2.0
28.4
8.9 48.0 118.4 36.7
98.0 208.4 64.4 148.0 289.4 92.2 198.0 388.4
-18.3
-1.0
30.2
9.4 49.0 120.2 37.2
99.0 210.2 65.0 149.0 300.2 92.8 199.0 390.2
-17.8
0.0
32.0
31
10.0 50.0 122.0 37.8 100.0 212.0 65.6 150.0 302.0 93.3 200.0 392.0
°C =
°F =
5
9
(°F - 32)
9
( x
°C) + 32
5
NOTES
32
4 Tesseneer Drive,
Highland Heights,
Kentucky 41076-9753
GENERAL CABLE, ANACONDA
and CAROL are trademarks of
General Cable Technologies Corporation.
©2008.
General Cable Technologies Corporation.
Highland Heights, KY 41076
All rights reserved.
Printed in USA
Phone:
1.888.593.3355
Fax: 1.800.335.1270
International Tel.: +1.859.572.8000
International Fax: +1.859.572.8058
www.generalcable.com
Form No. INS-0084-0908
35013