Copyright AIST Reprinted with Permission. Presented at the 2013 Iron and Steel Technology Conference and Exposition (AISTech 2013). Maintenance grounding is a traditional and proven method for protecting electrical workers during medium voltage switchgear maintenance. When properly applied, it eliminates dangerous differences in electric potential, and can redirect harmful current during events such as unforeseen induced voltage from motors and generators, accidental bus contact with adjacent live parts, or human error that causes equipment to be re-energized.

1. New Approaches for Maintenance
Grounding in Medium Voltage Switchgear
Joe Richard
Senior Marketing Specialist
Schneider Electric
David Mabius
Engineering Manager
Schneider Electric

2. Electrical Maintenance Standards
OSHA 1910. 269 - Electric Power Generation,
Transmission, and Distribution
 OSHA Standard governing maintenance of Electrical Generation, Transmission,
and Distribution Equipment.
 States the conditions that must be met for a reasonably safe work environment.
NFPA 70E – Handbook for Electrical Safety in the
Workplace, 2012
 Industry Standard for meeting the requirements of OSHA 1910.269.
 Article 120 lays out six steps for creating an Electrically Safe Work Condition
According to both standards, current carrying portions of electrical
equipment must be considered live until they have been grounded and
verified.

3. Hazards of Electrical Maintenance
Human Error:
 Misread/Outdated Drawings
 Not following Lock Out/Tag Out Procedures
 Improper Grounding
 Dropped Tools
 Original Installation Errors
External Sources of Energy:
 UPS
 Renewable Energy (Solar, Wind)
 Generators and Microturbines
 Capacitor Banks

4. Traditional Methods
Manual Grounding
 Cable Clamps
 Bus Bar Clamps
 Ground Ball and Socket Clamps
 Exposed to Live Conductors
 Full PPE
Ground and Test Device
 Most are never maintained
 Most users are untrained

5. Integral Grounding Switches
Benefits
 Allows for the grounding of
conductors before switchgear
panels are removed
 Easy to use when designed with
safety interlocks
 Easy to secure
 Time saved in Grounding
Procedure
 Reduced probability of human
error

6. Integral Grounding Switches
Quality Requirements
 Tested and approved for available fault current
 Effective bonding of switch to ground bus
 Robust construction to withstand mechanical fault forces
 Source of voltage indication (LLIs)
 Safety interlocking

7. 52
52 52 52
Applications: Example
52
52
525252
O CC
C C C C C C
Fully Energized
Utility 1 Utility 2

8. 5252
52
52 52 52
Applications: Example
52
52
52
O OC
C C C O O O
Open Circuit Breakers
Utility 1 Utility 2

9. 5252
52
52 52 52
Applications: Example
52
52
52
O OC
C C C O O O
Open Disconnect Switches
Utility 1 Utility 2

10. 52 52 52
52
52 52 52
Applications: Example
52
52O OC
C C C O O O
Close Grounding Switches
Utility 1 Utility 2

11. 52 52 52
52
52 52 52
Applications: Example
52
52O CC
C C C C C C
Close Circuit Breakers
Equipotential Zone
Utility 1 Utility 2

12. Thank You
Joe Richard
Senior Marketing Specialist
Schneider Electric
David Mabius
Engineering Manager
Schneider Electric