OSHA & Arc Flash. Scott Ray Distribution Project Engineer POWER Engineers, Inc.

Transcription

1 OSHA & Arc Flash Scott Ray Distribution Project Engineer POWER Engineers, Inc.

2 Outline Arc Flash Overview OSHA Overview Arc Flash Study Next Steps Why This Method? Questions Methodology Steps Analysis

3 Arc Flash Overview What is Arc Flash? The thermal (heat) energy given off by an uncontrolled electrical arc through open air. Referred to as the incident energy in cal/cm 2. Can be between conductors or between conductors and ground.

4 Arc Flash Overview Four types of energy released in an arc: 1. High Temperature Heat Energy Temperatures can soar well above that of the surface of the sun (~10,000 F) in just a fracmon of a second 2. Blast Percussion Sound Damage VaporizaMon of solids to gases Shrapnel 3. High Intensity Light Flash 4. Super Heated Ball of Gas Plasma

5 Arc Flash Overview Requirements and Standards NESC OSHA NFPA 70E IEEE 1584

6 OSHA Overview (d)(1) Employer shall assess the workplace for hazards which necessitate the use of PPE Select and have employees use appropriate PPE to protect employees from hazards idenmfied in the hazard assessment

7 OSHA Overview This secmon covers the operamon and maintenance of electric power generamon, control, transformamon, transmission, and distribumon lines and equipment.

8 OSHA Overview

9 Arc Flash Study Methodology Methodology Follows the IEEE 1584 nine steps: 1. Collect the system and installamon data 2. Determine the system modes of operamon 3. Determine the bolted fault currents 4. Determine the arc fault currents 5. Find the protecmve device characterismcs and duramon of arcs

10 Arc Flash Study Methodology Methodology Follows the IEEE 1584 nine steps (cont d): 6. Document the system voltages and classes of equipment 7. Select the working distances 8. Determine the incident energy for all equipment 9. Determine the flash- protecmon boundary for all equipment

11 Arc Flash Study Steps 1 and 2: Standard data collecmon UMlize substamon single- lines to determine stamon operamng modes UMlize WindMil model to determine feeder modes of operamon

12 Arc Flash Study Steps 3 and 4: UMlize WindMil model to calculate fault currents on the system from substamon to out on feeders Three- phase faults for use in IEEE 1584 arc- in- box calculamons Single- phase faults for use in overhead lines and ARCPRO calculamons

13 Arc Flash Study Step 5: UMlize LightTable database for system protecmve devices

14 Arc Flash Study Steps 6 and 7: Use system voltages and equipment to determine: Arc Gaps Working Distances Used to develop PPE calorie curves

15 Arc Flash Study Analysis PPE Calorie Curve Development Use voltage, equipment type, arc gap and working distance informamon to develop curves Develop curves for: 5.0 cal/cm 2 Threshold for arc rated faceshield 8.0 cal/cm 2 Minimum ramng worn by personnel 40.0 cal/cm 2 Maximum desired ramng to be worn by personnel

16 Arc Flash Study Analysis Curve Development Generate Mme current points Develop curves via two methods: 1. IEEE 1584 EquaMons 2. ARCPRO Import points into LightTable to develop Mme current curves

17 Arc Flash Study Analysis Using LightTable Compare: ProtecMve device curves Calorie curves Fault currents 2.0 second cutoff Mme For each locamon give a ramng/grade Pass CondiMonal Pass Fail

18 Arc Flash Study Analysis Pass The U2 relay curve fully protects the 5.0, 8.0 and 40.0 cal/cm 2 curves from range of potenmal fault currents

19 Arc Flash Study Analysis CondiMonal Pass The U3 relay curve doesn t fully protect the 5.0, 8.0 and 40.0 cal/cm 2 curves from range of potenmal fault currents However protects up to the 2.0 second evacuamon Mme

20 Arc Flash Study Analysis Fail The U4 relay cover fails to protect the 5.0 and 8.0 cal/cm 2 curves from range of potenmal fault currents (40.0 cal/cm 2 curve is a condimonal pass)

21 Next Steps Use the results as part of overall arc flash safety program LocaMons with Pass condimons no addimonal analysis needed CondiMonal pass condimons determine whether results are acceptable for situamon and work to be performed Fail condimons Use WindMil and LightTable to adjust protecmve device sekngs

22 Why This Method? Doesn t require a detailed model Can be used independent of fault analyses Arc flash analysis models use IEEE empirically derived models only applicable for certain scenarios

23 QuesMons? Scom Ray POWER Engineers, Inc. (503)