Ways to Reduce Arc Flash Energy. Robert E. Fuhr, PE PowerStudies, Inc.

Transcription

1 Ways to Reduce Arc Flash Energy Robert E. Fuhr, PE PowerStudies, Inc.

2 Arc Flash Produces Excessive Noise Pressure Wave Extreme Heat Toxic Gases, Vapors, Particles Flying Molted Metal Particles Shrapnel

3 Arc Flash Produces Energy in the form of Thermal Radiation Chemical Mechanical Electrical

4 Arc Flash Hazard Analysis Key Steps Use NFPA 70E* Tables, IEEE 1584, or Lee Equations to Determine Arc Flash hazard distance Incident energy levels *Use with Extreme Caution!!!!

5 Arc Flash Hazard Analysis Key NFPA 70E Table 130.7(C)(11) to determine Hazard/Risk Category Required PPE Steps

6 Arc Flash Hazard Analysis Key Steps Create Arc Flash Warning Labels showing the details.

7 IEEE 1584 Guide for Performing Arc-Flash Hazard Calculations Provides the steps and equations Arc Flash Energy Equations Require: Equipment Bolted Fault Currents Arcing Fault (AF) Current Upstream Protective Device Clearing Times

8 Arc Flash Energy Level Also Dependent Upon Operating Voltage Gap Length Type of Grounding Greatest Effect on Calculations 1. Time Upstream Device Operates 2. Working Distance 3. Available fault current

9 Fault Current vs. Incident Energy Current Vs Energy Levels (Time Sec) I n c i d e n t E n e r g y Fault Current Energy PPE Class

10 Time vs. Incident Energy Time Vs Energy Levels (Fault Current 30 ka) In c id e n t E n e r g y Device Operating Time Incident Energy PPE Class

11 Distance vs. Incident Energy Distance Vs Energy Levels (Time 0.5 Sec & Fault = 60 ka) I n c i d e n t E n e r g y Distance (Inches) 0 Energy Class

12 Reduce Energy Level to Zero De-energize the equipment!

13 Next Best Solution Increase the Work Distances Lower the Fault Current Reduce Device Clearing (Trip) Times

14 Design, Modifications, Retrofits, & Work Procedures Reduce the fault current. Clear the arcing fault as quickly as possible without sacrificing coordination. 3 2 E P S N 2- XFMR-UTILS XFMR-UTILS 3-MSWBD MAIN SWBD 5-Fdr to ATS-E ATS 260 Amp 1 6-PNL-A MAIN PNL-A A

15 Reduce Fault Current Use Several Smaller Transformers / Substations vs. One Large One Current Limiting Reactors

16 Fuses Operates Extremely Fast (If in current limiting range.) Reduces Current and Energy levels Change Fuse Types Faster Clearing Curves CL vs. Expulsion Different types Reduce Fuse Ampere Size

17 Fuses Fused vs. Un-Fused Disconnect Switches

18 Fuse ka 3-6 Sec This Fuse is Current Limiting Clearing time is seconds 5 ka

19 Circuit Breakers Current Limiting Breakers Reduces currents and energy levels

20 Circuit Breakers Specify breakers with Solid State Trip Units Long, Short & Instantaneous (If Possible) Set Short Time PU & Delay as low as possible.

21 Thermal Magnetic Trip Unit Thermal Unit is Fixed Instantaneous Fixed Adjustable

22 Thermal Magnetic Breaker Sec 4 ka Sec 20 ka

23 Solid State Trip Unit Long Time Pickup (LTPU) Long Time Delay (LTD) Varies for each Trip Unit! Some Functions are Not Adjustable! Short Time Pickup (STPU) Short Time Delay (STD) Instantaneous (I) Short Time Delay I2T-IN (I2T)

24 Solid State Trip Sec SQ D NW 40H 4000 Amp Micrologic 6 ka Sec 30 ka Sec 100 ka

25

26 Circuit Breakers Use Same Settings for: Main and Bus Tie Primary & Secondary Devices Use Zone Interlocking between Mains and Feeders.

27 Circuit Breakers & Switchgear Flash Sensing Breakers Differential Protection Arc Flash Venting Switchgear

28 Relays Change Relay Types and Curves Solid State Programmable Curve Shapes (Definite or Mod Inverse) Reduce MV Feeder Relay Pickup

29 Modification of Work Procedures Eliminate Paralleling of Transformers Eliminate work between Transformer Secondary and Main Breaker. Implement Faster Trip Times for Maintenance Work Circuit Breakers Relays

30 Modification of Work Procedures Use Infrared Windows

31 Modification of Work Procedures Work at a Greater Distance Remote Breaker Racking

32 Summary Reduce Arc Flash Energy by: Increasing the Worker Distance Reducing Fault Currents Decreasing the Trip Times

33 Need more Information Articles Links Specifications for Power System Studies Short Circuit Protective Device Coordination Arc Flash Hazard

34 Who are we? Electrical Engineering Consulting Firm We Specialize in performing Power System Studies 90% of our business is in performing Power System Studies

35 Where are we located? Our office is located in Maple Valley, WA. Near Seattle