High Voltage High Voltage Electrical SafetyElectrical Safety

The Shocking TruthThe Shocking Truth

Course ObjectiveCourse Objective • Regulation OSHA and NFPA 70ERegulation OSHA and NFPA 70E• Qualified Person Unqualified PersonQualified Person Unqualified Person• Level of Hazards (Level of Hazards (Hazard Classification and CategoryHazard Classification and Category) ) • Location Planning and Procedures Location Planning and Procedures • Approach LimitsApproach Limits• Lockout and Energized Electrical PermittingLockout and Energized Electrical Permitting• Insulated Equipment and ToolsInsulated Equipment and Tools• Personal Protective Equipment (Arc Flash Personal Protective Equipment (Arc Flash

and Blast rating)and Blast rating)

Objective ContinuedObjective Continued

• Special PrecautionsSpecial Precautions• Electrical DiagramsElectrical Diagrams• Equipment DetailsEquipment Details

• Examples of EquipmentExamples of Equipment

Arc Flash HazardsEvery 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?Who is at risk?Some of the employees at risk from arc Some of the employees at risk from arc flash hazards include mechanics, flash hazards include mechanics, electricians and HVAC personnel. The most electricians and HVAC personnel. The most dangerous tasks include:dangerous tasks include:

•Removing or installing circuit breakers or Removing or installing circuit breakers or fuses fuses •Working on control circuits with energized Working on control circuits with energized parts exposed parts exposed •Racking circuit breakers in and out of Racking circuit breakers in and out of switch gear switch gear •Applying safety grounds Applying safety grounds •Removing panel covers Removing panel covers •Low voltage testing and diagnosticsLow 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:How can we reduce the risk:

Understand how to reduce the Understand how to reduce the probability of an arc flash event and its probability of an arc flash event and its effects.effects.By begin with an Arc Flash Analysis and By begin with an Arc Flash Analysis and Assessment that includes:Assessment that includes:•Potential arc flash incident energy Potential arc flash incident energy levels levels •Flash protection boundary distances Flash protection boundary distances •Safety training Safety training •Selecting the correct personal Selecting the correct personal protection equipment (PPE) protection equipment (PPE) •Proper Electrical equipment labelingProper 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:An employer is required to:•Conduct an arc flash hazard analysis of the Conduct an arc flash hazard analysis of the workplace. workplace. •Implement qualified and general worker Implement qualified and general worker safety training based on the arc flash hazard safety training based on the arc flash hazard analysis results. analysis results. •Establish shock and flash protection Establish shock and flash protection boundaries. boundaries. •Provide protective clothing (PC) and personal Provide protective clothing (PC) and personal protective equipment (PPE) that meet ANSI protective equipment (PPE) that meet ANSI standards. standards. •Put warning labels on equipment (see Put warning labels on equipment (see example at right). A future edition of the arc example at right). A future edition of the arc flash safety code may require more extensive flash safety code may require more extensive labeling (inset) that includes flash hazard labeling (inset) that includes flash hazard boundary and PPE levels.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.

Selection of Personal Protective EquipmentNFPA 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 Other Personal Protective Equipment Equipment

•Jackets

•Hard Hat

•Shield

•Gloves Tested 00

•Gloves Leather

Insulated ToolsInsulated Tools

MetersMeters&&

Testers Testers

Types of Electrical BoxesTypes of Electrical Boxes

480 volt Switch Gear

                                                                                               

                            1.Open/close pushbuttons permit local electrical operation. 2.Dual-purpose manual handle for charging and tripping switch operators when control power is not available. 3.Operator targets show switch operator status (charged or discharged) and position (open or closed). 4.Optional remote-control receptacle for attaching remote-control station. Permits open-close operation from adjacent area. 5.Charging shaft for manual charging in the event power is lost. 6.Switch-position target indicates whether Mini-Rupter® Switch is open or closed. 7.Decoupler indicator shows whether switch operator is coupled to Mini-Rupter Switch. 8.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. 9.Bolted covers provide access to input connectors and receptacles, and terminal blocks. 10. Micro-AT® Source-Transfer Control

E-Vault

Dry Transformer

Power Closet

480 Switch Gear

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

SummaryArc 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