OSHA & Arc Flash Scott Ray Distribution Project Engineer POWER Engineers, Inc.
Outline Arc Flash Overview OSHA Overview Arc Flash Study Next Steps Why This Method? Questions Methodology Steps Analysis
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.
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
Arc Flash Overview Requirements and Standards NESC OSHA NFPA 70E IEEE 1584
OSHA Overview 1910.132(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
OSHA Overview 1910.269 This secmon covers the operamon and maintenance of electric power generamon, control, transformamon, transmission, and distribumon lines and equipment.
OSHA Overview
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
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
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
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
Arc Flash Study Step 5: UMlize LightTable database for system protecmve devices
Arc Flash Study Steps 6 and 7: Use system voltages and equipment to determine: Arc Gaps Working Distances Used to develop PPE calorie curves
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
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
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
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
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
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)
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
Why This Method? Doesn t require a detailed model Can be used independent of fault analyses Arc flash analysis models use IEEE- 1584 empirically derived models only applicable for certain scenarios
QuesMons? Scom Ray POWER Engineers, Inc. (503) 892-6771 scom.ray@powereng.com