HomeMy WebLinkAbout05.b. Receive update on a recent ArcFlash incident at Substation 33 Page 1 of 6
Item 5.b.
CENTRAL SAN
Y-109-ITMEN ME
April 20, 2021
TO: ENGINEERING AND OPERATIONS COMMITTEE
FROM: NATE MORALES, SENIOR ENGINEER
REVIEWED BY: NEIL MEYER, PLANT MAINTENANCE DIVISION MANAGER
STEVE MCDONALD, DIRECTOR OF OPERATIONS
ROGER S. BAILEY, GENERAL MANAGER
SUBJECT: RECEIVE UPDATE ONARECENTARCFLASH INCIDENTAT SUBSTATION
33
Attached is a staff presentation to summarize an ArcFlash incident that occurred at Substation 33 on
March 8, 2021 at the wastewater treatment plant. There were no personnel injuries and no significant
equipment or property damage resulting from this incident. District Treatment Plant Safety and
Maintenance staff are developing new work requirements. These include changes to the Contractor Safety
Plan requirements and new work precautions for the Standard Maintenance Workflow Procedures to help
prevent any future ArcFlash occurrences. This is an informational update only and no Board or Committee
action is required.
Strategic Plan Tie-In
GOAL FOUR: Workforce Development
Strategy 2—Foster relationships across all levels of Central San, Strategy 3— Inspire employee engagement, Strategy
4—Meet or exceed industry safety standards
GOAL FIVE:Infrastructure Reliability
Strategy 1—Manage assets optimally to prolong their useful life, Strategy 3—Protect personnel and assets from
threats and emergencies
ATTACHMENTS:
1. Presentation
April 20, 2021 EOPS Regular Committee Meeting Agenda Packet- Page 30 of 46 *Amended Agenda, including meeting ti
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REVIEW OF ARCH FLASH
INCIDENT AT SUBSTATION 33
AND RECOMMENDATIONS
April 20, 2021
_- Engineering & Operations Committee
Nate Morales, Senior Engineer
OUTLINE OF PRESENTATION
• What is an "arc flash" and common causes
• Description of the March 8, 2021 incident
• Consequences
• Overview ; lullll
• Actions Taken
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April 20, 2021 EOPS Regular Committee Meeting Agenda Packet- Page 31 of 46 *Amended Agenda, including meeting ti
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WHAT IS AN "ARC FLASH"
• An arc flash is an unplanned electrical discharge that
passes through air from one conductor to another, or to
the ground
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COMMON CAUSES OF ARC FLASH INCIDENTS
• Touching a live, exposed electrical conductor
with a metal tool or part
• Exposed live parts, loose connections
• Insulation damaged gaps, or wear and tear
• Dust, debris, and corrosion on electrical conductors
April 20, 2021 EOPS Regular Committee Meeting Agenda Packet- Page 32 of 46 *Amended Agenda, including meeting ti
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DESCRIPTION OF INCIDENT
• On March 8, an electrical contractor was replacing a
variable frequency drive (VFD) in Substation 33
• While working, a small panel of the motor control cabinet
(MCC)fell onto the 480V electrical busbar and caused an
arc flash
• District Controls, Operations & Maintenance staff were
present
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CONSEQUENCES OF INCIDENT
• No personnel injuries
• No significant process impact, equipment or
facilities damage
• After a brief North Clarifier power outage, the MCC
was safely reenergized
April 20, 2021 EOPS Regular Committee Meeting Agenda Packet- Page 33 of 46 *Amended Agenda, including meeting ti
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LOCATION
Substation 33
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OVERVIEW OF INCIDENT
MCC 3361 in Sub 33 Point of
contact with
MCC frame
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•, Point of
{� contact with
busbar
Outline of bus barrier
n its installed position
Damaged busbar Bus Barrier that separates
480V busbars from wireway.
This plate should have been
fastened to MCC.
In this instance it was loose
4 and fell back onto the busbar.
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April 20, 2021 EOPS Regular Committee Meeting Agenda Packet- Page 34 of 46 *Amended Agenda, including meeting ti
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CORRECTIVE ACTION
• A consultant Electrical Engineer determined the busbar does not need
to be replaced.
• Contractor instructed to confirm bus barriers are secure before working
on MCCs
• Safety&Maintenance staff completed an Incident Root Cause Analysis
Report with corrective actions
• CMMS work orders will be used to track follow up action including PMs
for electrical staff to visually inspect wireways and bus barriers.
• Proposed new electrical work procedures for contractors and District
staff
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QUESTIONS
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April 20, 2021 EOPS Regular Committee Meeting Agenda Packet- Page 35 of 46 *Amended Agenda, including meeting ti