Electric Shock Incident from Transformer Test .ppt

Electric Shock Incident from Transformer Test

1. Lawrence Livermore National Laboratory
Electric Shock Incident from Transformer Test
on January 2008
Sherman Chao, Facility Representative
at Livermore Site Office
Performance Measures x.x, x.x, and x.x

2. 2
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Summary of Events
1.New Transformerswere installed to replace old ones.
2.2 groups of Electricians workingon testing the sameTransformer
Circuit
1st group -“Megger” insulation teston Transformer
2nd group -continuity teston Transformer’s junction box at a
different floor.
3.2nd group electrician received a shockfrom Meggering by 1st
group via neutral wire.
4.LLNL Conducted Investigation with Fac Rep as
observer/participant

3. 3
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Electrician 1 activities
•Testing insulationon the new transformer on 1st floor.
•Using Hi DC voltage, Low current Instrument
Megger @ 1kV DC @ 1mA (2mA max.)
Note: GFI’s are set at 4 to 6mA AC.
•Presumed no else was workingon the system.
•Isolated the transformerby opening Circuit breakers but
not neutral
•Primary Power LOTO’d

4. 4
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Transformer Insulation Testing
To basement
switchgear
Transforme
r
Intended Current Path
Insulation
Unintended Current Path
1

5. 5
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Transformer and Name Tag
1500/2000 KVA 3 Phase
13,800 v to 480/277v
Transformer

6. 6
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Shock Source -Megger Instrument
To Test
Transformer
Insulation
Resistance

7. 7
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Electrician 2
Performing Continuity Testing on same system
Received shock to Electrician-2 while labeling
transformer busin Junction box.
Shock Source-Megger insulation resistance tester @
1,000 v. & 1mA.
Injury very minor

8. 8
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Continuity Testing wires at Buss Tap Junction Box
Switch Gear
Circuit Breaker
Buss Tap
Junction Box Switch Gear
Circuit Breaker
A
B
C
N
A
B
C
N
B151 Rm B137
Downstairs
Jumper
C to N
Electrician 2
From
Transformer
Conduit
Continuity Tester

9. 9
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Buss Junction Box in Basement
Buss Junction
Box (closed)
Continuity Tester

10. 10
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Continuity Test and Shock Site
Junction Box
Site of the shock
Buss Bars
Buss Bars C
phase

11. 11
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Current Path that shocked Electrician-2
1
1
2
Unintended Current Path

12. 12
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Direct Cause
Operation of the Megger instrument, by
Electrician-1 testing the transformer insulation,
shocking Electrician-2 working on the same
distribution system.

13. 13
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Root Cause
Failure of LLNL management to implement adequate
systems, procedures and controls
•Subcontractor management’s daily supervision was
poor

14. 14
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Contributing Causes
1.Work being performed concurrently.
2.Lack of Communication
3.Performing insulation test without isolating the
transformer
4.Lack of hazard understanding.
5.Lack of design drawings.

15. 15
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Contributing Causes (continued)
6.Incorrect Presumption of Open Breakers
7.Lack of any effective Work Controls
8.Lack of responsible person

16. 16
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Judgments of Need
1.Need Work Controlsformultiple buildings and systems
2.Need to use project drawings
3.Need to formalize daily tailgate meetings
4.Need a policy and enforcement of multi-team work.
5.Need to establish a process, for Megger tests
6.Need trainingonthe Meggertest process
7.Need training on new Work Control Procedures

17. 17
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Other Comments
1.A lack of technical inquisitiveness
2.Circuit Isolation with no LOTO.
3.Slow in reporting
4.LLNL Rigorous Work Control Process
5.Electrical Severity Calculation
6.Lessons Learn Video

18. 18
Option:UCRL# Option:Directorate/Department Additional Information
S&T Principal Directorate—Engineering
Questions?