40 Technical Information Mining 40 Proper Splices While it is true that no splice is as good as a new cable, the use of quality materials and proven techniques can dramatically improve the service life of the cable splice. A well-made splice has the following characteristics: 1. High tensile strength — the splice cannot be easily pulled in two 2. Balanced conductors — equal tension on each conductor 3. Small outside diameter — the splice can be passed easily through existing cable guides 4. Low electrical resistance 5. Adequate insulation 6. High resistance to fatigue 7. A covering that is capable of keeping moisture from entering the cable interior Shielding Remember that an ungrounded shield is dangerous and should be treated as an energized conductor. The shield must be grounded at least at one end and preferably at two or more locations. It is recommended that shields be grounded at all cable terminations and splices. Stress cones should be installed at all high- voltage shield terminations. 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 (in 2 ) by 30,000 psi. Bending Radius The recommended Insulated Cable Engineers Association (ICEA) minimum bending radii are as follows: • Braid-shielded portable cables ? 5000 V — 6 times the cable diameter • Braid-shielded portable cables > 5000 V — 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 AMPACITY CORRECTION FACTORS APPROXIMATE FOR ALL CABLE VOLTAGES Correction factors are listed below for various ambient temperatures. When cables are used with one or more layers wound on a reel, the ampacities should be derated as follows: VOLTAGE DROP Approximate for all cable voltages — three conductor cables A MB I EN T T E MP ER A T U RE C OR R E C T I ON F A C T OR S F OR I N S U L AT I O N S R AT E D AT : ? C 9 0? C 10 1.26 20 1.18 30 1.10 40 1.00 50 0.90 N U MB ER O F L A Y ER S M U L T I P L Y A M P A C I T I E S B Y 1 0.85 2 0.65 3 0.45 4 0.35 90 ?C 6 0 - C Y C L E P H A SE - TO -P H A SE V O L T A G E D R O P P ER A MP ERE P E R 1 , 0 0 0 F T A T P O W E R F A C T O R S O F : C O N DU C T O R S I Z E ( A W G o r k c m i l ) 80 % 90 % 10 0 % 6 0.82 0.90 0.95 4 0.54 0.58 0.60 2 0.35 0.38 0.38 1 0.29 0.31 0.30 1/0 0.24 0.25 0.24 2/0 0.20 0.20 0.19 3/0 0.16 0.17 0.15 4/0 0.14 0.14 0.12 250 0.12 0.12 0.10 300 0.11 0.11 0.08 350 0. 10 0.09 0.07 400 0.09 0.08 0.06 500 0.0 8 0.07 0.05 Installation and Engineering Information