Optical Arc Flash Protection and Installation Experience Boris A. Vega

1. Optical Arc Flash Protection and Installation Experience Boris A. Vega Regional Sales Manager, ABB Inc. MEMSA Annual Meeting and Technical Symposium September 4, 2008

2. Discussion Topics • Arc Flash Hazards – Cause, Effect, Energy Levels and PPE. • Optical Arc flash protection. • Reducing Clearing Time and Comparison of Mitigating Options. • Optical Arc Protection Case Study and Conclusions.

3. Arcing Incidents Do Happen 5 to 10 arc flash accidents occur daily in the United States Capshell, Inc. - Chicago based research firm specializes preventing workplace injuries and death “One large utility has discovered an average of 1 arc-flash injury every 18 months for the past 54 years.” IEEE Std 1584 – 2002, 10.3

4. Arc Flash Hazards An uncontrolled arc causes Hot gases, melt drops and thermal radiation may cause damage even farther away A rapid temperature rise may lead to a violent explosion Toxic chemical compounds may be formed at high temperatures

5. Arc Flash Hazards • Electric Arcs can reach temperatures of 34,000˚F. • The arcs can vaporize metal, burn skin, and ignite clothing. • Vaporized copper expand 67,000 times in volume. • High pressures can develop in enclosures, causing covers and molten metal to fly. • The intensity of an arc may exceed normal office lighting by 2,000 times.

6. Causes of Internal Arc Faults • Failure to follow operating procedures. • Tools, foreign objects, rodents, etc. • Gradual component or insulation breakdown due to ageing. • Improper maintenance. • Operation outside the rating envelope. • Mechanical and interlock failures.

7. Breaker Racking Arc Accident

8. Without operator,25% With operator workingin the switchgear, 65% With operator in front of a closed door, 10% Arc Flash Hazards When?

9. Arc Flash Accident

10. NFPA Hazard Levels

11. Typical PPE Suit Requirements 4 1 0 3 2

12. Clearing Time is Critical • IEEE 1584™ Final Step in Incident Energy Calculation • For applications up to 15 kV • For applications above 15 kV cal/cm2 cal/cm2 where: t = arcing time = relay time + breaker time

13. Clearing Time is Critical Time Overcurrent protection can take several cycles even seconds to operate Operating Time (ms)

14. Optical Arc Flash Protection • Detects light flash • Supervised by current • Tripping normally requires both light and fault current • First generation – Introduced in the early 1990’s • Uses single-point light receptors (lens sensors) • Second generation – Introduced in 1999 • Uses “long fiber” continuous optical sensors • Extremely fast – typical 2.5 ms operating time

15. Typical Optical Fiber Sensor Routing

16. Effect of Reduced Clearing Time

17. Reducing Relay Time • Temporary instantaneous settings for faster operation • (+) Fairly fast (about 2 cycles) • (+) Inexpensive to implement • (–) Activation requires operator action • (–) Normal coordination may be sacrificed • (–) Failure to deactivate could result in undesired tripping • Install high impedance bus differential protection • (+) Fairly fast (about 2 cycles) • (–) Requires CTs on all circuits… expensive to implement • (–) Concerns with CT saturation • (–) Cannot protect feeder cable zone areas

18. Reducing Relay Time • Install zone interlocking scheme • (+) Fairly fast (5 -10 cycles); some delay required for blocking • (+) Inexpensive to implement • (–) Requires communication between devices • Install dedicated optical arc flash protection • (+) Ultra fast (2.5 ms or 0.15 cycles) • (+) Fairly inexpensive to implement • (+) No coordination with downstream devices required • (+) Can support sectionalized arc flash zones and circuit breaker failure schemes

19. Arc Flash Relays – Case Study • Detromovice Power Plant – Czech Republic – June 26, 2002 • Closed breaker racked in (mechanical interlocks bypassed) • Minimal damage • Soot damage – confined to the affected frame • Breaker rosette connectors replaced, breaker cell cleaned • No injuries!

20. Arc Flash Relays – Case Study • Fertilizer plant – Uusikaupunki, Finland – 2003 • Event occurred one day after arc flash relay installed • Event resulted from operation error • Disconnect switch failed to interrupt capacitive current on an energized, unloaded cable • Fault cleared before any significant damage occurred • Plant was restored to service in about 4 hours • No injuries!

21. Optical Arc Flash Relay Applications • Ideally suited to gear with sealed interrupters (vacuum, SF6) • Where no exposed arcing normally takes place • Application in air magnetic gear requires study • Where arcing takes place within arc chutes • Successfully tested with 1200A, 500MVA GE Magneblast™ breakers • More tests on low voltage switchgear planned

22. Conclusions • Fast response is critical to minimizing arc flash hazards • Faster clearing times yields many benefits • Lower incident energy • Lower hazard levels • Lower PPE levels • Optical arc flash relaying among the fastest available protection • Actual arc flash events have proven optical arc flash protection works

23. Thank You