Metoodos para reducir af

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REDUCING ARC FLASH RISK WITH THE APPLICATION OF PROTECTIVE RELAYS
Copyright Material IEEE Paper No. PCIC-2009-43 Ray Luna Member IEEE GE Multilin League City, TX ray.luna@ge.com Brian Cassidy P.E. Senior Member IEEE Bayer MaterialScience Baytown, TX brian.cassidy@bayerbms.com Jesus Franco Senior Member IEEE Bayer MaterialScience Baytown, TX jesus.franco@bayerbms.com

Abstract - The exposure toan arc flash high incident energy fault to technicians operating low and medium voltage switching equipment is a daily hazard in the workplace and there is an opportunity to improve safety. While PPE protects for first and second degrees burns it does not provide sufficient protection for the impact and forces that a high incident energy arcing fault produces and the gases released. One solutionis to reduce the incident energy of the arcing fault. This paper analyzes methods to reduce the exposure of personnel to high-energy arcing faults, and also defines a method to determine the limits of coordination among protective devices to identify where the selectivity could be jeopardized. Index terms: Arc flash, coordination, arc flash hazards, fault studies. I. Introduction

the fault iscleared, the less the caloric energy that is produced, consequently, the less molten material, shrapnel, and gases released. Analyzing the settings of existing relaying systems and applying the multiple protection, control, and communication functions of modern protection relays provide implementation solutions of an electrical arc flash safety program in industrial facilities. In a Petrochemicalfacility there are two electrical operating modes in a typical workday: Normal Mode and Switching Mode. The content of this paper is developed around these two scenarios, which are defined as follow: Normal Mode: The normal operating mode is when the power equipment is energized and the load is being served to the production process units with no human interactions. If a non-arcing fault occurs,the protective equipment detects the fault and disconnects the faulted equipment very quickly and safely since there is no arc to damage the equipment. Conversely, if an arcing fault occurs, the protective relaying and other protective equipment should detect the fault but the current flowing will be less than the non-arcing fault and the time to clear the fault could be longer depending on thecalculated settings and the equipment installed. The settings of protective relays and the selection of other protection equipment, such as medium and low voltage fuses and low voltage circuit breakers, should be set to minimize the incident energy to a lowest caloric value possible without jeopardizing selectivity. Switching Mode: The switching operation mode is defined as when personnel executeelectrical switching procedures to disconnect loads or to restore power to equipment that was previously disconnected for maintenance or repairs. During this mode of operation, the protection relays settings and the installed fuses and low voltage breakers combine to determine the fault clearing time and the level of incident energy developed if an arcing fault should occur. During switchingactivities of the power system, the personnel performing maintenance or modifications around energized equipment will be exposed to the dangers of an arcing fault, and the safety of the personnel takes priority over the selectivity of the protection apparatus. This protective apparatus must be set to ensure the reduction of

Extensive studies on arc flash phenomena have been developed since Ralph Leeintroduced the Arc Flash as a hazard in the work place [1]. This paper acknowledges these works and introduces awareness to mitigate the effects of the Arc Flash Hazard (AFH) by utilizing modern technology offered in protective relays, as well as to maximize the utilization of existing relays installed in electrical substations. NFPA 70E[3] defines flash hazard as a dangerous condition associated...
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