High Voltage Electrical Safety The Shocking Truth

Course Objective Regulation OSHA and NFPA 70E Qualified Person Unqualified Person Level of Hazards (Hazard Classification and Category) Location Planning and Procedures Approach Limits Lockout and Energized Electrical Permitting Insulated Equipment and Tools Personal Protective Equipment (Arc Flash and Blast rating)

Objective Continued Special Precautions Electrical Diagrams Equipment Details Examples of Equipment

Arc Flash Hazards Every year, more than 2,000 workers are treated in burn centers with severe arc flash injuries. The flash is immediate, but the results can cause severe injuries that last months, years—even a lifetime. In some cases, they may cause death. Fortunately, arc flash hazards can be reduced by following safety precautions and using the recommended personal protective equipment.

What is an arc flash hazard? Think of an arc flash as a short circuit through the air. In an arc flash incident, an enormous amount of concentrated radiant energy explodes outward from electrical equipment. The explosion creates pressure waves that can damage a person’s hearing, a high-intensity flash that can damage their eyesight and a superheated ball of gas that can severely burn a worker’s body and melt metal. The pressure waves can also propel loose material like molten metal, pieces of damaged equipment, tools and other objects, through the air.

Where do arc flash hazards occur? A hazardous arc flash can occur in any electrical device, regardless of voltage, in which the energy is high enough to sustain an arc. Potential places where this can happen include: Panel boards and switchboards Motor control centers Metal clad switch gear Transformers Motor starters and drive cabinets Fused disconnects Any place that can have equipment failure

Who is at risk? Some of the employees at risk from arc flash hazards include mechanics, electricians and HVAC personnel. The most dangerous tasks include: Removing or installing circuit breakers or fuses Working on control circuits with energized parts exposed Racking circuit breakers in and out of switch gear Applying safety grounds Removing panel covers Low voltage testing and diagnostics

What are the effects of an arc flash explosion? The effects of an arcing fault can be devastating. The intense thermal energy can cause severe burns in a fraction of a second. One of the major causes of electrical burns and deaths to workers is ignition of non-fire rated clothing due to an arcing fault. Treatment can require years of skin grafting and rehabilitation. A victim may never return to work or enjoy quality of life. Treatment costs can exceed $1,000,000 per case. Other considerations include loss of life, potential litigation fees, loss of process, potential fines and escalation of insurance premiums.

Did you know? The temperature of an arc flash can reach 35,000 degrees Fahrenheit – about four times as hot as the surface of the sun.

How can we reduce the risk: Understand how to reduce the probability of an arc flash event and its effects. By begin with an Arc Flash Analysis and Assessment that includes: Potential arc flash incident energy levels Flash protection boundary distances Safety training Selecting the correct personal protection equipment (PPE) Proper Electrical equipment labeling

Electrical Safety-Related Work Practices If electrical equipment must remain energized while servicing and maintenance is performed, electrical safety-related work practices must be utilized by qualified employees as outlined by OSHA in 29 CFR 1910.331 – 1910.335. In addition to OSHA’s requirements, NFPA 70E Standard for Electrical Safety in the Workplace 2004 Edition contains requirements for performing a flash hazard analysis.

Flash Hazard Analysis and Flash Protection Boundary Prior to commencing work on electrically energized conductors > 50 volts, NFPA 70E Article 130.3 requires that a flash hazard analysis be performed to identify work tasks that must be performed while electrical equipment remains energized. Instead of performing a detailed analysis, however, Table 130.7 (C)(9)(A) (Hazard Risk Category Classifications) may be utilized to identify various job tasks and the corresponding hazard risk category. NFPA 70E Article 130.3 (A) requires employers to establish a flash protection boundary – a distance from exposed energized electrical parts at which an employee could sustain a second degree burn if an electric arc flash were to occur. Employees performing work on energized conductors inside this boundary must be protected with appropriate Personal Protective Equipment (PPE). In most cases, the flash protection boundary for electrical systems 600 volts and below will be four (4) feet.

What are the NFPA 70E Guidelines? An employer is required to: Conduct an arc flash hazard analysis of the workplace. Implement qualified and general worker safety training based on the arc flash hazard analysis results. Establish shock and flash protection boundaries. Provide protective clothing (PC) and personal protective equipment (PPE) that meet ANSI standards. Put warning labels on equipment (see example at right). A future edition of the arc flash safety code may require more extensive labeling (inset) that includes flash hazard boundary and PPE levels.

Arc Flash Marking on Field Breakers In addition to the flash hazard analysis and PPE requirements specified in NFPA 70E, the 2002 National Electrical Code® (NEC) requires field labeling of circuit breaker panels and electrical disconnects to warn qualified employees of the potential arc flash hazards: Article 110.16 Flash Protection: "Switchboards, panel boards, industrial control panels, and motor control centers in other than dwelling occupancies, that are likely to require examination, adjustment, servicing, or maintenance while energized, shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment." An example of an arc flash label is shown.

(including voltage testing) rated < 240 volts. Selection of Personal Protective Equipment NFPA 70E Table 130.7 (C)(9)(A) lists various work tasks and the corresponding hazard risk category (0 through 4). Once the hazard risk category has been determined, Table 130.7 (C)(10) [Protective Clothing and Personal Protective Equipment (PPE) Matrix] is consulted to determine the appropriate PPE. An example is listed below. Example: Employee is working on an energized panelboard (including voltage testing) rated < 240 volts. Required PPE: Task is listed as a hazard risk category one (1). In addition to voltage rated gloves, Table 130.7 (C)(10) specifies the following PPE: Flame retardant clothing (long-sleeve shirt and pants), hard hat and safety glasses.

Other Personal Protective Equipment

Jackets Hard Hat Shield Gloves Tested 00 Gloves Leather

Insulated Tools

Meters & Testers

Types of Electrical Boxes 480 volt Switch Gear

Open/close pushbuttons permit local electrical operation.                                                                                                                            Open/close pushbuttons permit local electrical operation. Dual-purpose manual handle for charging and tripping switch operators when control power is not available. Operator targets show switch operator status (charged or discharged) and position (open or closed). Optional remote-control receptacle for attaching remote-control station. Permits open-close operation from adjacent area. Charging shaft for manual charging in the event power is lost. Switch-position target indicates whether Mini-Rupter® Switch is open or closed. Decoupler indicator shows whether switch operator is coupled to Mini-Rupter Switch. Decoupler handle permits convenient decoupling of switch from switch operator for functional testing of source-transfer schemes and exercising of switch operator, without disturbing power circuit. Bolted covers provide access to input connectors and receptacles, and terminal blocks.  Micro-AT® Source-Transfer Control

E-Vault

Dry Transformer

Power Closet

480 Switch Gear

Disconnect found during Infrared Inspection Disconnect found during Infrared Inspection. Failed due to loose connection inside the switching mechanism. Switch was found to be in the energized state

Cover Completely Blown Off

Summary Arc flash hazards pose a serious risk to employee safety; proper safe work practices must be utilized. Electrical equipment > 50 volts must be deenergized and lockout/tagout followed prior to servicing and maintenance unless doing so would increase hazards or is infeasible. Remember, convenience is not an acceptable reason for keeping equipment energized during servicing and maintenance. If electrical equipment must remain energized during servicing and maintenance, NFPA 70E should be consulted to determine flash hazard boundaries as well as required PPE. Finally, circuit breakers and electrical disconnects must be marked to warn qualified employees of potential arc flash hazards. For more information on electric arc flash hazards or assistance on performing a flash hazard analysis, please contact W. Jon Wallace, CSP, MBA