Do not exceed pulling tension of 1000 pounds per grip. “Use basket weave cable grip for cable runs less than 200 feet, for cables less than 2 inches in diameter, and for cables between switchgears and transformers. Manufacturer’s Instructions) (NFPA 70, NEC 110.3(B)) Pull cable at constant velocity not less than 15 feet per minute and not greater than 50 feet per minute. Use power-assisted cable pulling equipment for long or difficult pull or pulls with several transitions. Manufacturer’s Instructions) (NFPA 70, NEC 110.3(B))Ĭable may be pulled manually for short, easy runs. For large conductors or long pulls, assist reel rotation manually or use a power out reel. Carefully control the rate of cable reel rotation. Ensure cable reels are level to reduce drag. Support cable reels with adequately sized reel jacks and reel axle. Use guides adequately sized for the cable being pulled and for the duct, along with properly sized bell and duct adapters. Provide physical protection of cables, such as flexible cable guides or feed-in tubes, at the entrance of manholes, underground ducts, and conduits. “Avoid abrasion and other damage to cables during installation. (Manufacturer’s Instructions) (NFPA 70, NEC 110.3(B))” “Use a torque-balance pulling line or an adequately sized swivel joint between pulling line and the cable pulling attachment to prevent cable rotation during pulling operations. Minimum bending radius for all cables with metallic shield is 12 times the diameter of the individually shielded conductors or 7 times the overall diameter, whichever is greater.( IEEE 576, 7.3)Ĭonduit shall be sized in accordance with Table 1 in Chapter 9 of the NEC. ![]() “Avoid sharp bending of the cable at the first pulley in overhead installations by locating the pay-off reel far enough away from the first pulley that the lead-in angle is kept relatively flat. Use adequate lubrication of the proper type to reduce friction in conduit and duct pulls. The percent fill requirement shall not be exceeded. Table 3 (IEEE 576, 5.1) See Attachment.īending radius of cables without metallic shielding or armor: Table 4 (IEEE 576, 7.1) See Attachment.īending radius of cables with metallic armor: Table 5 (IEEE 576, 7.1) See Attachment.Įnsure adequate clearance between duct or conduit diameter and cable diameter. (IEEE 576, 4.1.1)Ĭable sidewall pressure limitation – The ratio of pulling tension out of the bend to the radius of the bend of the cable shall be limited to minimized cable damage. The maximum pulling tension for copper conductor should not exceed 0.008 times circular-mil area. When the calculated pulling tension is close to (or within 10% of) the maximum pulling tension, use tension gauge during pulling. (NFPA 70, NEC 300.18)Ĭonsult the cable manufacturer for cable maximum allowable / recommended pulling tension. The raceway systems shall be installed complete prior to installation of MV power cables. Duct banks in loose back fill or low strength CDF/FTB may flex instead of fracturing.Medium Voltage Cable Installation and Commissioning (Rated 5KV through 35KV) ![]() There seemed to be some concern that inadequately reinforced concrete duct banks could facture during earth movements. I have heard various discussions from civil engineers about which duct protection approach is best for handling movement from earthquakes. In some applications red dye is also added as an attempt to discourage dig-ins. Sand and pea gravel have horrible thermal properties, so these materials are only used for conduits carrying instrumentation cables or power cables with negligible thermal loading.įTB and CDF both provide some protection again accidental dig-ins, while still allowing some ability to expose conduits if needed. FTB is very similar to CDF but is specifically designed to have good thermal transfer. Depending on the thermal properties of the native soil, we may require the use of Fluidized Thermal Backfill (FTB) for installations with thermal constraints. For large power cables, thermal considerations are really important. ![]() One important distinction is thermal constraints.
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