1. CHREID 2008 ELECTRICAL SAFETY Introduction and Overview of Safety Clayton H. Reid September, 2010

2. CHREID 2008 2 ELECTRICAL HAZARDS Electrical shock Electrical arc-flash Electrical arc-blast

3. CHREID 2008 3 ELECTRICAL SHOCK (part one of two) Body resistance Wet or dry skins are major factors of resistance Circuit voltage Amount of current flowing through the body Current through the body Area of contact Duration of contact

4. CHREID 2008 4 ELECTRICAL ARC-FLASH Arco electric-flash Body Burn

5. CHREID 2008 5 What is an Arc Flash?

6. CHREID 2008 6 ELECTRICAL Arc-Blast Rapid expansion of the air caused by an electrical arc, referred to as an electrical arc-blast or explosion

7. CHREID 2008 7 CONTRIBUTING FACTORS TO ELECTRICAL ACCIDENTS Faulty Insulation Improper grounding Loose connections Defective Parts Ground faults in equipment Unguarded live parts Failure to de-energize electrical equipment when it is being repaired or inspected Intentional use of obviously defective and unsafe tools Use of tools or equipment too close to energized parts Tools left in electrical cubicle

8. CHREID 2008 8 PREVENTING ELECTRICAL ACCIDENTS Largely preventable through safe work practices Examples of some safe work practices –De-energizing electrical equipment for inspection and repair –Keeping electrical and equipment properly maintained –Exercising caution when working near exposed energized lines or equipment –Using appropriate personal protective equipment and insulated tools

9. CHREID 2008 9 ELECTRICAL SAFETY ENVIRONMENT, SAFETY AND HEALTH PRINCIPLES (used by DOE) Plan Work Analyze Hazards Control Hazards Perform Work Feedback and improve

10. CHREID 2008 10 ELECTRICAL ACCIDENTS CAUSED BY ONE OF THE FOLLOWING Unsafe work practices Unsafe equipment or installation Unsafe environment

11. CHREID 2008 11 REQUIREMENTS Knowledge/Familiarity Mechanical Interlocks Electrical Interlocks Bus Transfer Procedures Lock, Tag and Try Procedures

12. CHREID 2008 12 REQUIREMENTS Workers: Trained and Qualified One Line Diagrams: Up- to- date and attached to procedures Test Equipment: Good working condition and calibrated PPE( Personal Protective Equipment) Good Working Condition and tested per standards

13. CHREID 2008 13 SAFETY INTERLOCKS IN MEDIUM VOLTAGE STARTERS Protective Barriers for Safe Operation of MV Starter Isolating Switches Design And Function Of Safety Interlocks Maintenance of Safety Interlocks in MV Starters

14. Copyright © 2007 Rockwell Automation, Inc. All rights reserved. 14 3 Pole, Non-Load Break Isolation Switch 3 Current Limiting Power Fuses (Clip-On or Bolted Type) 3 Phase Vacuum Contactor 3 Bar Type Current Transformers 1 High MV Cell Control Power Transformer is located behind the contactor Power Cell Compartment

15. Copyright © 2007 Rockwell Automation, Inc. All rights reserved. 15 1 High MV Cell Power Cell Compartment The power cell is designed to allow easy access without the need to remove components.

16. Copyright © 2007 Rockwell Automation, Inc. All rights reserved. 16 Two High MV Cell Power Cell Compartment The power cell in a Two High structure includes, as standard, a swing-out Low Voltage panel, allowing for increased working area.

17. Copyright © 2007 Rockwell Automation, Inc. All rights reserved. 17 l The standard components housed in the panel are: l Normal-Off-Test selector switch l Male test power receptacle l Rectifier Bridge l CR1 and CR2 control relays l Motor protection relay(s) Low Voltage Compartment

18. Copyright © 2007 Rockwell Automation, Inc. All rights reserved. 18 When in the “OFF” position the isolation switch is connected to “Ground Potential” via grounding pins. Non-load Break Isolation Switch

19. Copyright © 2007 Rockwell Automation, Inc. All rights reserved. 19 Non-load Break Isolation Switch It is mechanically and electrically interlocked with the contactor to ensure it can’t open or close when the contactor is closed. It is also mechanically interlocked with the power cell door.

20. CHREID 2008 20 Maintenance Aids Voltage detectors Viewing windows Infrared sight glass Grounding balls

21. Voltage Checking Devices Non Contact Voltage Detectors (NCVD) Voltage Indicator (low and high voltage) Voltmeters CHREID 2008 21

22. CHREID 2008 22 Voltage Detectors

23. CHREID 2008 23 Voltage Detectors

24. CHREID 2008 24 Voltage Detectors

25. CHREID 2008 25 Voltage Detectors

26. Grounding Balls CHREID 2008 26

27. CHREID 2008 27 Grounding Cable

28. CHREID 2008 28 Infrared Sight glass

29. CHREID 2008 29 Infrared Scanning

30. Copyright © 2007 Rockwell Automation, Inc. All rights reserved. 30 The higher voltage does not effect the function of the product it only affects the form of the product: –size –electrical clearances –interlocking –components Medium Voltage and Low Voltage

31. CHREID 2008 31 ArcShield Two-High: Top Cable Entry/Exit New plenum design enables top cable/conduit connections! 1512B 1512A 1591A

32. 32 Arc vent on the unit roof –Aluminum plate designed to open under high pressure associated with arc flash conditions –Offset to rear of structure (allows use of LV wireways) –Installers must not step on this area (suitable warning label is provided) ArcShield Overview

33. Unusual Electrical Events CHREID 2008 33

34. CHREID 2008 34 CASE HISTORY #1 MCC starter unit

35. CHREID 2008 35 CASE HISTORY #2 The Reluctant Skip

36. CHREID 2008 36 CASE HISTORY #3 Incorrect testing with a multimeter

37. CHREID 2008 37 CASE HISTORY #4 Travelling arc and amperes gone beserk

38. CHREID 2008 38 CASE HISTORY #5 Mystery of the missing fishtape