GE Mark VIe System Manual page 135

The control system has no special or non-standard installation requirements, if installed in compliance with all of the
following:
• The NEC or local codes
• With SRS designed to meet IEEE Std 1100
• Interconnected with signal/power-level separation as defined later
This section provides equipment grounding and bonding guidelines for control and I/O cabinets. These guidelines also apply
to motors, transformers, brakes, and reactors. Each of these devices should have its own grounding conductor going directly
to the building ground grid.
• Ground each cabinet or cabinet lineup to the equipment ground at the source of power feeding it.
− See NEC Article 250 for sizing and other requirements for the equipment-grounding conductor.
− For dc circuits only, the NEC allows the equipment-grounding conductor to be run separate from the circuit
conductors.
• With certain restrictions, the NEC allows the metallic raceways or cable trays containing the circuit conductors to serve
as the equipment grounding conductor:
− This use requires that they form a continuous, low-impedance path capable of conducting anticipated fault current.
− This use requires bonding across loose-fitting joints and discontinuities. See NEC Article 250 for specific bonding
requirements. This chapter includes recommendations for high-frequency bonding methods.
− If metallic raceways or cable trays are not used as the primary equipment- grounding conductor, they should be used
as a supplementary equipment grounding conductor. This enhances the safety of the installation and improves the
performance of the SRS.
• The equipment-grounding connection for the control cabinets is plated copper bus or stub bus. This connection is bonded
to the cabinet enclosure using bolting that keeps the conducting path's resistance at 1 ohm or less.
• There should be a bonding jumper across the ground bus or floor sill between all shipping splits. The jumper may be a
plated metal plate.
• The non-current carrying metal parts of the equipment covered by this section should be bonded to the metallic support
structure or building structure supporting this equipment. The equipment mounting method may satisfy this requirement.
If supplementary bonding conductors are required, size them the same as equipment-grounding conductors.
6.5.2 Building Grounding System
This section provides guidelines for the building grounding system requirements. For specific requirements, refer to NEC
article 250 under the heading Grounding Electrode System.
The guidelines below are for metal-framed buildings. For non-metal framed buildings, consult the GE factory.
The ground electrode system should be composed of steel reinforcing bars in building column piers bonded to the major
building columns.
• A buried ground ring should encircle the building. This ring should be interconnected with the bonding conductor
running between the steel reinforcing bars and the building columns.
• All underground, metal water piping should be bonded to the building system at the point where the piping crosses the
ground ring.
• NEC Article 250 requires that separately derived systems (transformers) be grounded to the nearest effectively grounded
metal building structural member.
• Braze or exothermically weld all electrical joints and connections to the building structure, where practical. This type of
connection keeps the required good electrical and mechanical properties from deteriorating over time.
Installation Guidelines
Public Information
GEH-6721_Vol_I_BP System Guide 135