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.
Strategize a Smooth Tenant-to-tenant Migration and Copilot Takeoff
New Approaches for Maintenance Grounding in Medium Voltage Switchgear
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Misread/Outdated Drawings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