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Importance of Arc Flash Analysis (Arc Flash Loss Prevention) Provides minimum requirements to prevent hazardous electrical exposures to personnel and.

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Presentation on theme: "Importance of Arc Flash Analysis (Arc Flash Loss Prevention) Provides minimum requirements to prevent hazardous electrical exposures to personnel and."— Presentation transcript:



3 Importance of Arc Flash Analysis (Arc Flash Loss Prevention) Provides minimum requirements to prevent hazardous electrical exposures to personnel and ensure compliance with regulatory requirements applicable to electrical systems

4 Regulatory Requirements (elements necessary for Worker Safety) OSHA = Shall Provide Worker Safety NFPA 70E = How to provide Worker Safety Employer Responsibility = Execution Focus on safety, promote training, use best practices

5 Electrical Hazards Consist of: Electric Shock Arc Flash Arc Blast Other Hazards

6 Electric Shock An electric shock occurs when electric current passes through the body. This can happen when touching an energized part. If the electric current passes through the chest or head, death can result.

7 Effects of Electrical Current in the Human Body Below 1 milliampere: - Generally not perceptible 1 milliampere: - Faint tingle 5 milliamperes: - Slight shock felt; not painful but disturbing. Average individual can let go. Strong involuntary reactions can lead to other injuries. 6–25 milliamperes (women): - Painful shock, loss of muscular control* 9–30 milliamperes (men): - The freezing current or " let-go" range.* Individual cannot let go, but can be thrown away from the circuit if extensor muscles are stimulated. 50–150 milliamperes: - Extreme pain, respiratory arrest, severe muscular contractions. Death is possible. 1,000–4,300 milliamperes: - Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely. 10,000 milliamperes: - Cardiac arrest, severe burns; death probable* If the extensor muscles are excited by the shock, the person may be thrown away from the power source. Source: W.B. Kouwenhoven, " Human Safety and Electric Shock," Electrical Safety Practices, Monograph, 112, Instrument Society of America, p. 93. November 1968.

8 Arc Flash/Blast An arc flash (also known as arc blast) is a sudden, explosive electrical arc that results from a short circuit through air. The air in the vicinity of an arc flash is heated to between 5,000 and 35,000 degrees in no more than 1/1000 of a second, becoming an electrically-conductive plasma. The sudden heating can cause a shock wave blast equivalent to several sticks of dynamite and carrying vaporized metal and shrapnel

9 Safe Work Practices OSHA Potential for shock or other injury Working on or near live exposed parts Practices must be consistent with the extent of the hazard NFPA 70E Requires deenergizing Requires worker to be qualified Requires hazard analysis Electrical work permit

10 NFPA 70E Requirements for Working on or Near Live Parts Perform Arc Flash Analysis Select Personal Protective Equipment (PPE) Complete Energized Electrical Work Permit Complete Task Specific Training Complete a job briefing session

11 Arc Flash Analysis Establish Shock Protection Boundary (approach boundaries) – used to reduce shock hazard Conduct Flash Hazard Analysis Establish Flash Protection Boundary Used to reduce arc flash hazards and may reduce arc blast hazards Select Personal Protective Equipment Analysis per NFPA 70E requires update every 5yrs

12 Approach Boundary to Live Parts Limited (42 in) Restricted (12 in) Prohibited (1 in) Based on system voltage = 480V NFPA 70E, Annex C, Figure C.1.2.4

13 Flash Protection Boundaries (FPB) Using NFPA 70E, the methods to determine FPB Defaults (i.e. tables) Perform Analysis that uses Calculation Methods

14 Levels of Exposure

15 Personal Protective Equipment (PPE)

16 PPE Designed to protect specific areas of the body Eye Protection Neck, Face, Head, Chin Arm & Hand Protection Body Protection Leg & Foot Protection

17 PPE - Gloves Voltage rated gloves are REQUIRED for all voltage testing above 50 volts

18 OSHA/NFPA 70E General Industry Requirements OSHA (a) Employees exposed to potential electrical hazards shall use protective equipment that is appropriate for the specific areas of the body to be protected and for the work to be performed NFPA 70E Provides standards for equipment Hazard Risk Table PPE Matrix Extensive detail for worker protection Protective Equipment

19 OSHA Fines For non-compliance, OSHA may audit a facility and issue fines Most recently: U.S. Postal Service $420,000 (pending) – single facility

20 A Facilitys Electrical System A facilitys electrical system operates as a single, dynamic system. Its performance is dependent on the properties of each component and the loads connected to it. Many facilities expand project by project using different design and construction teams. Even though each specific project may be well planned and designed, its often the case that the area of work specific to the project is limited to only a portion of the existing electrical distribution system. In addition, due to the need for maintenance and emergency repairs, system components are often replaced with devices that are different than originally installed due to availability and cost. Because of these occurrences, its common that no one has an overall and complete understanding of the entire electrical system.

21 Tools Most firms that provide arc flash services utilize specially designed software for electrical system modeling in short circuit and arc flash studies. Such as SKM Power System Tools

22 Process/Approach to Complete a Study As-built Documentation The usual starting point is to gather all existing drawings an Owner has and sort it by location and date. (One-Line Documentation) Verification Survey each site and verify one-line documentation. Acquire missing info. PD types/sizes/settings, cable lengths, Xfmr impedance values Loading Load the information into SKM and run Short Circuit, Coordination, Arc Flash

23 Ex: How to Initiate a Study Large School System Herndon HS Pyramid Langley HS Pyramid McLean HS Pyramid Aldrin ESChurchill Road ES Chesterbrook ES Armstrong ESColvin Run ES Franklin Sherman ES Clearview ESForestville ESHaycock ES Dranesville ES Great Falls ES Kent Gardens ES Herndon ESSpring Hill ESTimber Lane ES Hutchison ESCooper MSLongfellow MS Herndon MSLangley HSMcLean HS Herndon HS


25 Cluster Analysis Approach (5) field survey teams composed of (2) people each assigned to various sites within a cluster. All survey is schedule/time dependent. CLUSTERSITESPYRAMIDS TEAMEST. TIME (mo.) C1223A C2283B C3273C C4283D C5223E Following C1-C5 C6223A/E5 - 7 C7253C C8253B/D6 -8

26 1 ST Step - Collect Hard Copy Data Existing Building Documents -Electrical One-Line Diagrams -Floor Plans -Maintenance Documents

27 2 nd Step - Field Survey

28 Types of Equipment Surveyed

29 Gathering of Information During Survey Process Protective Device Information Location, (Room/Panel/Whats it feeding?) Make, Model, Manufacture AIC and Trip Plug Rating Settings

30 3 rd Step - Load the Data Build SKM One-Line Diagrams for each site Verify accuracy of information Acquire Utility Company contribution information Run/Review Short Circuit Calculations The maximum fault current can be calculated at each electrical buss in the system by knowing the properties of the power sources that will provide the current, and using the impedance values of the circuits that connect the busses Understanding the Duty Rating of the equipment by comparing the available fault current to the rating of the protective device

31 Build the Model in the Software

32 Run a Short Circuit Study Compare Protective Device Ratings Breakers/fuses Against the available 3-phase and SLG Fault currents.

33 Selective Coordination In order to be assured that all over current protection devices are coordinated, it is necessary to look at the time vs. current characteristic of each device and compare it to the characteristics of any upstream devices.

34 Coordination Example

35 Poor Coordination Main Breaker Trips, Shutting Down the Entire Switchboard

36 Adjustments to be Made Settings LTPU - Long time pick up LTD – Long time delay STPU – Short time Pickup STD – Short time Delay I²t – Short time delay bend INST – Instantaneous GFPU – Ground Fault Pick up GFD – Ground Fault Delay GFI²t – Ground Fault Delay bend

37 Improved Coordination

38 4 th Step - Arc Flash Evaluation Arc Flash Evaluation To calculate the available arc flash energy, it is necessary to perform a short circuit study to determine the magnitude of the current that will flow in a fault condition, and also a coordination study to determine the length of time it takes for an Over Current Protection Devices (OCPD) to clear the fault.

39 Arc Flash Analysis


41 5 th Step – Review Results/Recommendations Reports are generated based Existing (as is) conditions. Identifies the problem areas with bad coordination and high incident energy categories Reports are generated based on Recommendations (best scenario) to better coordinate devices and lower arc flash incident energy categories Begin Training Process

42 ON-SITE ELECTRICAL SAFETY TRAINING A balance of safety & technical training is essential for continuous improvement Designed to protect lives, prevent disabling injuries, and prevent damage to your facility & equipment. Personnel learn about personal safety for working on or around electrical systems Understand the proper use of materials and procedures for doing electrical work Hands-on practical instruction that they can immediately apply when they go back to their workplace Who should be trained? Anyone who works on or around any electrically energized equipment

43 Sample Arc Flash Label

44 Definition Qualified Person OSHA One who has received training in and has demonstrated skills and knowledge in the construction and operation of electric equipment and installations and the hazards involved. NFPA 70E Skills and knowledge related to the construction and operation of the equipment and has received safety training on the hazards involved.

45 Qualified Person Are they qualified to be working on live exposed electrical parts?

46 Perception of a Qualified Person Licensed Electrician = qualified employee Training Certificates Years of Experience I have never been hurt

47 Summary Dont assume that a person is qualified When in doubt, ask!!!! Their qualifications can affect you, your co-workers, and your company, the facility, etc… Best Practice: Whenever possible, work on electrical equipment de-energized Remember, regulations are minimum requirements Utilize best resources available Develop a principle directive (Golden Rule!)

48 Electrical systems design is at the core of our well established MEP firm. Leveraging our knowledge and expertise we can conduct arc flash analysis with precision, and provide recommendations based on our vast experience. A comprehensive study of the electrical system can provide the Owner the necessary tools to predict possible system failures, as well as the data necessary for safety, maintenance, and future planning. Quick Facts Established in employees 4 office locations Massachusetts North Carolina Vermont Virginia Multi-Disciplined Team 25 Mechanical 25 Electrical & Controls 15 Instrument Technicians 10 CAD/Admin Partial Client List Health Care Burlington Community Health Ctr. Fanny Allen Hospital Fletcher Allen Health Care Littleton Hospital University Health Care University of Vermont, Given Medical Upper Connecticut Valley Hospital VA Hospital BioTech & Pharmaceutical Astra Zeneca Baxter Bioscience Covidien Genzyme Johnson & Johnson LifeNet Lonza Biologics Mylan Technologies Novartis Pfizer Global R&D Siemens Medical Solutions Stryker Biotech Wyeth Geographically Percent of fee revenue MA RegionVT Region 40% 20% Mid-Atlantic Region Services Percent of fee revenue CommissioningEngineering Systems Integration 30% 35% Markets Percent of fee revenue Life Sciences, Health Care, R&D, Higher Education Microelectronics Industrial 70% 15%


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