Presentation on theme: "Copyright 2008 ABB - 1 All Rights Reserved Optical Arc Flash Protection and Installation Experience Boris A. Vega Regional Sales Manager, ABB Inc. MEMSA."— Presentation transcript:
Copyright 2008 ABB - 1 All Rights Reserved Optical Arc Flash Protection and Installation Experience Boris A. Vega Regional Sales Manager, ABB Inc. MEMSA Annual Meeting and Technical Symposium September 4, 2008
Copyright 2008 ABB - 2 All Rights Reserved 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.
Copyright 2008 ABB - 3 All Rights Reserved 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 Arcing Incidents Do Happen
Copyright 2008 ABB - 4 All Rights Reserved 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 An uncontrolled arc causes Arc Flash Hazards
Copyright 2008 ABB - 5 All Rights Reserved 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.
Copyright 2008 ABB - 6 All Rights Reserved 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.
Copyright 2008 ABB - 7 All Rights Reserved Breaker Racking Arc Accident
Copyright 2008 ABB - 8 All Rights Reserved When? With operator working in the switchgear, 65% Without operator, 25% With operator in front of a closed door, 10% Arc Flash Hazards
Copyright 2008 ABB - 9 All Rights Reserved Arc Flash Accident
Copyright 2008 ABB - 10 All Rights Reserved NFPA Hazard Levels Hazard Risk Category Typical Personal Protective Equipment (PPE) Required Minimum Arc Rating (cal/cm 2 ) 0 Non-melting, flammable materials with at least 4.5 oz/yd 2 N/A (1.2) 1FR pants and FR shirt, or FR coverall4 2Cotton underwear, plus FR shirt and FR pants 8 3 Cotton underwear, plus FR shirt and FR pants and FR coverall 25 4 Cotton underwear, plus FR shirt and FR pants and multilayer flash suit Moonsuit 40
Copyright 2008 ABB - 11 All Rights Reserved Typical PPE Suit Requirements
Copyright 2008 ABB - 12 All Rights Reserved Clearing Time is Critical IEEE 1584 Final Step in Incident Energy Calculation For applications up to 15 kV For applications above 15 kV where: t = arcing time = relay time + breaker time cal/cm 2
Copyright 2008 ABB - 13 All Rights Reserved Clearing Time is Critical Time Overcurrent protection can take several cycles even seconds to operate Operating Time (ms)
Copyright 2008 ABB - 14 All Rights Reserved Optical Arc Flash Protection Detects light flash Supervised by current Tripping normally requires both light and fault current First generation – Introduced in the early 1990s 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
Copyright 2008 ABB - 15 All Rights Reserved Typical Optical Fiber Sensor Routing
Copyright 2008 ABB - 16 All Rights Reserved Effect of Reduced Clearing Time
Copyright 2008 ABB - 17 All Rights Reserved 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
Copyright 2008 ABB - 18 All Rights Reserved 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
Copyright 2008 ABB - 19 All Rights Reserved 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!
Copyright 2008 ABB - 20 All Rights Reserved 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!
Copyright 2008 ABB - 21 All Rights Reserved 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
Copyright 2008 ABB - 22 All Rights Reserved 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
Copyright 2008 ABB - 23 All Rights Reserved Thank You