RISK MANAGEMENT TECHNIQUES FOR ELECTRICAL ARC FLASH RISKS. Steve Williams Engineers Australia Gladstone Local Group 30 January 2014

Transcription

1 RISK MANAGEMENT TECHNIQUES FOR ELECTRICAL ARC FLASH RISKS Steve Williams Engineers Australia Gladstone Local Group 30 January

2 SOME STATISTICS TO PONDER There are 10 reportable Arc Flash incidents involving more than one fatality every day in the USA. Studies indicate that up to 80% of all Electrical Worker injuries are not due to electric shock. They are due to external burn injuries created by the intense radiant heat energy of an electrical arc explosion. Are we any better in Australia at protecting our Electrical Workers? 2

3 SESSION OUTLINE 1. Arc Flash Refresher 2. Applicable Standards 3. Calculations & Studies 4. Assessing the Real Risks 5. Risk Mitigation Solutions 6. Labelling 7. Risk Management Plan 3

4 SESSION OUTLINE 1. Arc Flash Refresher 2. Applicable Standards 3. Calculations & Studies 4. Assessing the Real Risks 5. Risk Mitigation Solutions 6. Labelling 7. Risk Management Plan 4

5 SO WHAT IS AN ARC FLASH? Simply... An arc flash is a short circuit through the air. This electric arc releases an enormous amount of concentrated radiant energy which explodes outwards from energised electrical equipment. This creates an extreme hazard for anyone working on or near the energized equipment. In many instances, the arc is initiated by the actions of a person! 5

6 ARC FLASH WHY NOW? Higher Safety Awareness Statistics Less Electrocutions; More Burns Larger Systems & Higher Fault Currents Ageing Switchgear still in service Less Maintenance Staff Increased Litigation & Insurance Costs Software Technology Legislation 6

7 FIGURES ARE FRIGHTENING! Arc temperatures can reach up to ~20,000 C (4 times the temperature on sun s surface!) Gaseous copper is 44,000 times solid metal Pressure Waves can snap the heads off 10mm bolts (and burst ear drums!) Metal shrapnel 1,100 km per hour A 10,000 Amp arc blast at 480 volts is equivalent to approx. 8 sticks of dynamite. Clothing can be ignited several meters away 7

8 415V ARC FLASH EXAMPLE 8

9 415V ARC FLASH EXAMPLE 9

10 CAUSES OF ARC FLASH Accidental contact Dropped tools Faulty / Inappropriate Test Equipment Careless device removal / operation Corrosion / Conductive dust particles Deteriorating or poor insulation Misalignment of moving contacts Entry of foreign body (rodent, snake) 10

11 CAUSES OF ARC FLASH Accidental contact Dropped tools Faulty / Inappropriate Test Equipment Careless device removal / operation Corrosion / Conductive dust particles Deteriorating or poor insulation Misalignment of moving contacts Entry of foreign body (rodent, snake) 12

12 CAUSES OF ARC FLASH Accidental contact Dropped tools Faulty / Inappropriate Test Equipment Careless device removal / operation Corrosion / Conductive dust particles Deteriorating or poor insulation Misalignment of moving contacts Entry of foreign body (rodent, snake) 13

13 ARC FLASH CONSEQUENCES? Death of Victim Permanent Disfigurement Expensive Treatment Skin Grafts Hearing Loss Legal & Insurance Costs Loss of Production Costs Government Fines Company Reputation 14

14 SESSION OUTLINE 1. Arc Flash Refresher 2. Applicable Standards 3. Calculations & Studies 4. Assessing the Real Risks 5. Risk Mitigation Solutions 6. Labelling 7. Risk Management Plan 15

15 BUT FIRST... TERMINOLOGY Arc Flash Incident Energy The amount of energy a surface (or person) is exposed to at a set distance from an arc, typically the working distance. Units used are cal/cm 2 (!?) Arc Flash Boundary This is the distance from electrical equipment at which the incident energy equals 1.2 cal/cm 2. Within this distance, a person may experience second degree burns. Arc Flash Hazard Category A number (from 0 to 4) that aligns with defined Incident Energy ratings and identifies a corresponding level of PPE 16

16 HAZARD RISK CATEGORY 17

17 ARC FLASH STANDARDS No Australian Standard currently exists for Calculation Method IEEE 1584 Guide for Performing Arc Flash Hazard Calculations NFPA 70E Edition Standard for Electrical Safety in the Workplace CSA Z462 - Canadian Workplace Electrical Safety Standard (based on NFPA 70E) AS/NZS 4836: Safe working on or near low-voltage electrical installations and equipment 18

18 IEEE Provides most accepted method for calculating Incident Energy (cal/cm 2 ) and Flash Protection Boundary Equations based on extensive practical experiments As close to actual as possible (at the time) Applies up to 15kV, 106kA Applies to for different enclosure types Background physics now being challenged 19

19 NFPA70E US Standard for Electrical Safety in the Workplace Very USA-centric Specifies compulsory (in the USA) Arc Flash mitigation steps below: Electrical safety procedures Arc Flash Safety procedures Definitions of Hazard Risk Category (HRC) Use of Personal Protective Equipment (PPE) 2009 Edition well known 2012 Edition released Risks and Hazards 20

20 HRC RATED CLOTHING Hazard Risk Category (HRC) Clothing Description (as per NFPA70E-2009) 0 Non-melting material (Untreated Cotton) Min Arc Rating Cal/cm 2 NA (<1.2) 1 Arc-rated FR Shirt & Pants or FR Coverall 4 2 Arc-rated FR Shirt & Pants or FR Coverall 8 3 Arc-rated FR Shirt & Pants or FR coverall and arc flash suit with minimum required arc rating 25 4 Arc-rated FR Shirt & Pants or FR coverall and arc flash suit with minimum required arc rating 40 21

21 FACE, EYE & HAND PROTECTION Category 1 & 2 Arc rated face shield Leather Gloves Safety Glasses & Hard Hat Category 3 & 4 Arc rated flash suit hood Arc Rated Gloves Safety Glasses & Hard Hat 22

22 EXAMPLES OF PPE PPE Categories 1 & 2 PPE Categories 3 & 4 23

23 NFPA70E 2012: CHANGES Hand protection: Protector gloves shall be worn over rubberinsulating gloves for protection against arc flash and shock protection. Face Shield: Arc Rated face shield with Arc Rated balaclava for Cat 2 (alternatively, Arc Rated suit hood) AR not FR : Arc Rated clothing is now specified not Flame Resistant rated. Number of layers is no longer relevant!! Simplified Two Category PPE table can be used, after Arc Flash analysis is done! Changes to Equipment Labeling in USA DC Arc Flash: Separate tables are now provided for AC and DC Systems. 24

24 AS/NZS 4836:2011 Safe working on or near LV installations Revised in May 2011 to include Arc Flash Safety Emphasises Risk Assessment & Risk Management Competent person must identify risk for work within 3m of exposed energised conductors Assess and reduce risk, e.g. Establish Policy & Procedures, Switch off, Isolate/Tag, Erect Barriers, etc Lists suitable Safety Equipment and Tools (but FR not AR) PPE is not first line of defence, but to be used as a precautionary measure Does not utilise Incident Energies to select HRC & PPE 25

25 AS/NZS 4836:2011 TABLE 9.2 GUIDE TO THE SELECTION OF PERSONAL PROTECTIVE EQUIPMENT CURRENT EXCEEDING 100 CURRENTS UP TO AND CURRENTS EXCEEDING TASK A AND UP TO AND INCLUDING 100 A 400 A INCLUDING 400 A Work (isolated and verified) Switching, isolating, removing fuses or links Isolation verification, testing or fault finding Live electrical work Footwear Protective clothing (if required) Eye protection (if required) Gloves (if required) Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Footwear Protective clothing Eye protection Gloves (if required) Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Footwear Protective clothing Eye protection Gloves Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Footwear Protective clothing* Eye protection Insulating gloves Arc flash suit and hood (if required) Flame-resistant gloves (if required) Face shield (if required) Safety helmet (if required) Hearing protection (if required) Respiratory protection (if required) Footwear Protective clothing (if required) Eye protection (if required) Gloves (if required) Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Footwear Protective clothing Eye protection Gloves Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Footwear Protective clothing* Eye protection Gloves Arc flash suit and hood (if required) Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Face shield (if required) Footwear Protective clothing * Eye protection Safety helmet Insulating gloves Arc flash suit and hood (if required) Flame-resistant gloves (if required) Face shield (if required) Hearing protection (if required) Respiratory protection (if required) Footwear Protective clothing (if required) Eye protection (if required) Gloves (if required) Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Footwear Protective clothing Eye protection Gloves Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Footwear Protective clothing* Eye protection Gloves Face shield Arc flash suit and hood (if required) Hearing protection (if required) Safety helmet (if required) Respiratory protection (if required) Footwear Protective clothing * Eye protection Insulating gloves Flameresistant gloves Arc flash suit and hood Hearing protection Respiratory protection (if required) 26

26 SESSION OUTLINE 1. Arc Flash Refresher 2. Applicable Standards 3. Calculations & Studies 4. Assessing the Real Risks 5. Risk Mitigation Solutions 6. Labelling 7. Risk Management Plan 27

27 IEEE ENERGY CALCULATIONS Fault Levels Assumes 3 phase fault currents Arc Flash Currents are less Protection Clearing Time Accurate Protection device details Especially Instantaneous Settings Working Distance Depends on Voltage and Switchgear Busbar Gap & Type of Switchgear Depends on Voltage and Switchboard Grounding Method Grounded, Ungrounded, Resistance Grounded 28

28 CALCULATING... ARC CURRENTS 29

29 CALCULATING... INCIDENT ENERGY 30

30 CALCULATING... APPROACH BOUNDARY 31

31 CALCULATION ISSUES Complex mathematics More complex with multiple sources Induction motors contribute to Fault Level IEEE 1584 includes spreadsheet Must have bolted Fault Level Must have protection clearance time Analysis Software is the only real solution Fault Study & Protection Study are pre-requisites Data Collection is biggest issue 32

32 ARC FLASH STUDY PROCESS Accurate SLD, cables, Transformer data, large motors Computer Based Network Model Three Phase Fault Calculations Protection Coordination Study relays, CTs, fuses Optimise Relay Settings & Fuses Arc Flash Calculations Data Presentation Drawings & Tables 33

33 SESSION OUTLINE 1. Arc Flash Refresher 2. Applicable Standards 3. Calculations & Studies 4. Assessing the Real Risks 5. Risk Mitigation Solutions 6. Labelling 7. Risk Management Plan 34

34 INTERPRETING YOUR STUDY This is when: Confusion Conflict Misunderstanding Over-reaction Bad Decisions, can all occur! Mostly due to Lack of Knowledge 35

35 COMMON MISCONCEPTIONS 1. Arc Flash Protection = Arc Fault Containment False! Arc Flash calculations based on Door Open. 2. Need Calculated PPE for Normal Switching False! Switching is performed with the Door Closed. 3. HV Arc Flash is more dangerous than LV False! False! LV has higher Fault Currents & closer distances. 36

36 ASSESS THE RISKS Assess the REAL Risks Use Risk Management Principles Use standard Risk Assessment Matrix AS4360 on Risk Management Broad-brush Solutions generally fail! Use Simplified two Category system? 37

37 IDENTIFY BEST CONTROLS Use Hierarchy of Controls Individual Reviews Required But Keep It Simple! 38

38 SESSION OUTLINE 1. Arc Flash Refresher 2. Applicable Standards 3. Calculations & Studies 4. Assessing the Real Risks 5. Risk Mitigation Solutions 6. Labelling 7. Risk Management Plan 39

39 RISK MITIGATION SOLUTIONS #1 Isolate elsewhere Install phase indicators Implement remote controls Replace older protection devices Add additional protection devices Replace old & dangerous switchboards Install arc flash venting 40

40 RISK MITIGATION SOLUTIONS #2 Covers/ Barriers/ Shutters/ Insulation Protection settings changes Dual Setting Relays Maintenance Settings Add arc flash detection relays Remote racking of circuit breakers Provide better Test Equipment 41

41 RISK MITIGATION SOLUTIONS #3 Establish new procedures Establish Skills and Competencies Register Establish Change Control Procedures for Mods Standard designs & equipment specs for new equipment Regular updates to Arc Flash Studies Purchase appropriate PPE For electrical personnel For Substation kits 42

42 RISK ASSESSMENT EXAMPLE 1 415V MCC 4000A incomer 12 years old, modern design 2500kVA transformer - >40kA Fault Incomer : Rackable design; openings Arc Fault Containment What are the Risks? 1. Switching 2. Maintaining 43

43 RISK ASSESSMENT EXAMPLE 2 Dragline Sub >20 years old, older style No 66kV Breaker 6.6kV Vacuum Breakers Push-in Arc Fault Containment? What are the Risks? 1. Insertion & Removal 2. Maintaining 3. Switching 44

44 BUT...DOOR CLOSED? Conduct a Risk Assessment! Guidance: Task/Work based Tables in NFPA70E For Example 600V MCCs PPE CB operation with cover on 0 Reading panel meter 0 CB operation with cover open 1 Opening of Hinged doors 1 Working on energised parts 2* Removal of bolt covers 2* Check the fine print * 45

45 SESSION OUTLINE 1. Arc Flash Refresher 2. Applicable Standards 3. Calculations & Studies 4. Assessing the Real Risks 5. Risk Mitigation Solutions 6. Labelling 7. Risk Management Plan 46

46 SIMPLE LABELS Minimum requirement in NFPA70E 47

47 SAMPLE LABELS More complex, more detail Software can produce these 48

48 SESSION OUTLINE 1. Arc Flash Refresher 2. Applicable Standards 3. Calculations & Studies 4. Assessing the Real Risks 5. Risk Mitigation Solutions 6. Labelling 7. Risk Management Plan 49

49 AF RISK MANAGEMENT PLAN Addressing Arc Flash Risks long term Very few plants are static Equipment Modifications New Equipment & Packaged Equipment Staff changes Plant power system changes Utility changes Sign off by Management (& OHS) Protection against litigation (?) 50

50 AF RISK MANAGEMENT PLAN Employee Training Course Content and Facilitation Defining and Evaluating Competencies Existing Electrical Employees & Contractors New Electrical Employees & Contractors Non Electrical Personnel (even management?) Risk Assessment Techniques Refresher Courses & Toolbox Meetings 51

51 AF RISK MANAGEMENT PLAN Procedural Issues Standard Operating Procedures Standard Work Practices Access to Switchrooms Isolation Procedures Testing for Dead Procedures Switching Procedures 52

52 AF RISK MANAGEMENT PLAN Engineering Issues Accuracy & Validity of Electrical Drawings Equipment Identification & Labelling Equipment Specifications & Selection Equipment Additions & Modifications Upgrading older Equipment Fault Studies & Protection Settings Change Management Procedures Technical Support Arrangements 53

53 AF RISK MANAGEMENT PLAN PPE Solutions Site Selected PPE Categories Clothing Selection Clothing Replacement Programme Switchroom Kits Contract staff 54

54 IN CONCLUSION... We want to avoid someone getting hurt by this: Thank You 55