A closer look at bonding grounding electrodes (NEC 2011, article 250 requirements)

Author

PE, Dev Paul

Author_Institution

AECOM, Oakland, CA, USA

fYear

2011

fDate

9-13 Oct. 2011

Firstpage

1

Lastpage

7

Abstract

This paper describes the grounding design of a 480V, 3-phase, 4-wire power distribution system for a rail transit facility consisting of a passenger station and two separate parking garages. The authority having jurisdiction (AHJ) made an interpretation of NEC Section 250.50 that the grounding electrodes of the power panels at three different locations should be bonded to the main switchboard grounding electrodes by installing underground bonding conductors. Designers disagreed with AHJ and were opposed to such installation. Due to physical locations of the panels and the switchboard within the facility, such installation was impractical. To meet NEC requirements and to satisfy AHJ, a discussion of bonding of facility grounding electrodes is included in this paper. At locations where underground bonding conductors were not practical to install, bonding of structural steel members with metallic conduits for feeder cables that carry equipment grounding conductors between the main switchboard and various power panels act as bonding conductors.

Keywords

earth electrodes; electric conduits; overhead line conductors; power cables; power distribution; railway electrification; underground cables; 3-phase 4-wire power distribution system; NEC Section 250.50; bonding grounding electrodes; equipment grounding conductors; feeder cables; grounding design; metallic conduits; power panels; rail transit facility; structural steel members; switchboard grounding electrodes; underground bonding conductors; voltage 480 V; Bonding; Conductors; Electrodes; Elevators; Lighting; Switches; Authority Having Jurisdiction (AHJ); bonding conductor; critical loads; dc traction power; emergency loads; equipment grounding conductors (EGCs); grounding electrode conductors (GECs); passenger station; rail transit facility; standby generator; utility power transformer;

fLanguage

English

Publisher

ieee

Conference_Titel

Industry Applications Society Annual Meeting (IAS), 2011 IEEE

Conference_Location

Orlando, FL

ISSN

0197-2618

Print_ISBN

978-1-4244-9498-9

Type

conf

DOI

10.1109/IAS.2011.6074262

Filename

6074262