However, since control, instrumentation and communication cables run in separate steel conduit which - if it will be well bonding could create, also, a grounding effective path for power cables in the same duct bank. However, in this case, grounding with individual cable ground conductors (see 5.5.3.2) should be considered to avoid installation and bonding complications." When the cable is run underground, this grounding conductor should be located in the same direct burial or duct bank run as the cable. It is important that the ground conductors be run as close as possible to the circuit conductors, since this reduces the reactance of the fault current return path. The separate grounding conductor is run in the same conduit or cable duct as the outgoing power cable and is also used to ground the conduit or cable duct. Where a single cable leaves the cable tray, a branch grounding conductor is added and connected to the common grounding conductor and to the equipment enclosure or motor terminal box. Direct buried ducts shall be grounded by insulated, stranded copper ground wires installed in each duct. It is usually a bare stranded copper conductor connected to the main ground bus and fastened to the cable tray. 4/0 AWG bare stranded copper ground wire that is run within the duct bank and is grounded at both ends. A common equipment grounding conductor could be used for all cables in the same tray (it may also be used to ground the cable tray). From this main ground bus, a grounding conductor is run within the same raceway as the circuit conductors. Ufer is the name of the engineer who created it as a solution to significant grounding problems discovered by the U.S. The term Ufer does not appear in the Code, but many in the industry use it. It should be noted that in systems with impedance grounding, the grounding conductors should be connected to the neutral ground and not to the transformer neutral. A Ufer ground is slang for what the National Electrical Code (NEC) addresses as a concrete-encased grounding electrode. This may be the switchgear or the motor control center ground bus to which the supply transformer neutral is connected (solidly or through impedance) and that is solidly connected to the grounding grid. "It is recommended that a main ground bus be provided. All electric and communication manholes shall have a minimum of two (2) 5/8' x 80' copper-clad steel ground rods, installed outside and. Pull-in irons will be by Advance Concrete or approved equal. I am sure it could be also in other standards however this is what I found in "my collection".įrom IEEE-665 GENERATING STATION GROUNDING 5.5.3.1 Grounding with common equipment grounding conductor run to the neutral ground. A pull-in irons shall be installed directly across from each set of duct bank terminators, and new and future duct bank openings.
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