Arc Flash Safety 251

alternating current

AC. Electrical current that reverses direction at regularly recurring intervals of time. Alternating current usually reverses direction 60 times per second.

approach distances

The different distances at which an employee may approach a location that is susceptible to a hazard. Approach distances define boundaries to protect against arc flash and electric shock.

arc blast

The high-pressure sound wave that accompanies arc flash. Arc blast exposure can lead to severe hearing damage and even loss of brain function.

arc fault

A short circuit that creates an electric arc between exposed conductors. Arc faults are responsible for producing arc flash.

arc flash

An electrical explosion that results from an arc fault. Arc flash, or flashover, produces extreme heat and light and compromises the safety of employees who are exposed to it.

arc flash boundary

A border that defines the distance from an energized system at which an employee may experience second degree burns. Qualified employees must wear appropriate PPE to keep themselves safe when working inside an arc flash boundary.

arc flash risk assessment

A process used to analyze the potential for an arc flash event in a specific electrical system or piece of electrical equipment. Arc flash risk assessments determine if an arc flash hazard exists and identify appropriate safety measures, arc flash boundaries, and proper PPE.

arc flash suit hoods

Loose-fitting arc-rated PPE that covers the head and neck but not the eyes or nose. Arc flash suit hoods are typically part of an arc flash suit.

arc flash suits

An arc-rated clothing system that covers the entire body. Arc flash suits do not cover the hands and feet.

arc rating

A value that indicates the maximum level of incident energy to which PPE can be exposed and still function properly. The arc rating is based on the arc thermal protective value and must be displayed on the PPE.

arc thermal protective value

ATPV. A rating that indicates the amount of arc flash protection PPE can provide to the wearer. The arc thermal protective value is the basis for the arc rating displayed on arc flash PPE.

balaclavas

A close-fitting arc-rated hood that covers the head and neck but not the eyes or nose. Balaclavas are also called sock hoods.

calories per square centimeter

cal/cm². A unit used to measure incident energy. Calories per square centimeter describes the amount of thermal energy that strikes a surface at a certain distance.

circuit breaker

An overcurrent device with a component that bends when it detects excess current. Circuit breakers operate automatically when they detect overcurrent, but they can also be operated manually.

conductors

A material or element that allows free movement of electricity. Conductors require insulation to protect electrical systems from damage.

current

The flow of electricity. Current strength is called amperage and is measured in amperes (A) or amps.

decibels

dB. A unit of measurement that describes the intensity of a sound wave. Arc blast can produce sound waves that exceed 160 decibels.

digital multimeter

DMM. A device that can measure voltage, current, or resistance of a circuit. A digital multimeter is the most versatile and common meter used for electrical maintenance and troubleshooting.

direct current

DC. Electrical current that flows in a single direction. Direct current is the less common form of current.

eardrums

A vibrating membrane that stretches across the inner end of the ear canal. The eardrum can be damaged by arc blast.

earmuffs

A protective device that blocks excessive noise and debris from entering the ear. Earmuffs consist of two ear coverings connected by a band.

earplugs

A protective device that is inserted in the ear to block noise. Earplugs can be made from wax, cotton, foam, silicone, or rubber.

electric arc

The area in which electricity jumps from one conductor to another. Electric arcs produce extreme heat and light.

electric shock

The flow of electricity through the body. Severe electric shock can be fatal.

electrical burns

A burn caused by the flow of electrical current through tissue or bone. Electrical burns may result from arc flash events.

electrical hazard safety-toe shoes

Non-conductive footwear that prevents the wearer from completing an electrical circuit with the ground. Electrical hazard safety-toe shoes can protect against circuits of up to 600 volts in dry conditions.

electrically safe work conditions

ESWC. A state in which an electrical circuit and all of its components has been de-energized, locked and tagged out, tested, and grounded, if necessary. The NFPA requires employees to establish electrically safe work conditions before conducting any electrical work.

electrocution

Death due to electric shock. Electrocution can be caused by arc flash.

engineering

The department within a company responsible for creating the design specifications of a product. Engineering uses a product's marketing assessment to create product specifications.

eye protection

Any piece of PPE that protects the eyes. Eye protection includes safety glasses and safety goggles.

face shields

A rigid, transparent plastic sheet that covers the wearer's entire face to protect against debris or splashes. Face shields are often worn with goggles because they do not protect against impacts.

flame resistant

FR. A type of clothing that ignites but stops burning when the ignition source is removed. Flame-resistant clothing is used to limit the injuries that wearers sustain from burns if their clothing ignites.

flash hazards

A circuit or electrical system component that is at risk of producing an arc flash event. Flash hazards can be detected through arc flash hazard analyses.

flashover

An electrical explosion that results from an arc fault. Flashover, or arc flash, produces extreme heat and light and compromises the safety of employees who are exposed to it.

fuse

An overcurrent device with a component that melts when it detects excess current. Fuses melt to open the circuit and stop current flow when current passes a set level.

fuses

An overcurrent device with a component that melts when it detects excess current. Fuses melt to open the circuit and stop current flow when current passes a set level.

fusible element

A part in a fuse that melts to interrupt an electrical circuit. Fusible elements melt when current passes a set level.

generators

A device that converts mechanical energy into electrical energy. Generators typically contain several electrical conductors called windings.

ground fault circuit interrupter

GFCI. A type of switch that disables a circuit when it detects that current has strayed from its intended path. Ground fault circuit interrupters are especially useful when there is a chance that current may come into contact with a human being or water.

grounded

Safely connected to a neutral body, like the earth, that can absorb stray currents. Grounded equipment diverts current to prevent electric shock.

hard hat

A lightweight, protective head covering, usually made of plastic, used to protect the head from impacts, bumps, and electric shock. Hard hats have a shock-absorbing lining with a headband and straps that suspend the shell away from the skull and provide ventilation.

hearing protection

Various PPE that covers the ear in some way to protect a wearer's hearing. Hearing protection may include earplugs or earmuffs to protect hearing against the sound generated by arc blast.

high-amp power sources

A device that generates a large amount of electrical current. High-amp power sources can cause arc flash events.

hot wire

The conductor that supplies power from a source to a load. The hot wire is usually covered with black insulation.

incident energy

The thermal energy generated by an arc flash that strikes a surface at a specific distance. Incident energy is used to determine arc flash boundaries and personal protective equipment for specific tasks.

incident energy analysis

The process of calculating or computing the amount of predicted energy that an employee may be exposed to in the event of an arc flash incident. Incident energy analyses should be conducted by qualified personnel only.

Institute of Electrical and Electronics Engineers

IEEE. An international organization that creates standards for working with electricity and electrical components. The Institute of Electrical and Electronics Engineers produces a guide that helps make arc flash hazard calculations.

insulation

A material that isolates conductive materials and helps them transmit electricity effectively. Insulation is used to cover most conductors and wires.

kilometers per hour

km/h. A unit that indicates speed in the metric system. Kilometers per hour is equal to the distance traveled in kilometers divided by the time spent traveling in hours.

limited approach boundary

A border that defines the distance from an energized system at which an employee may experience electric shock. Employees must be qualified or directly supervised by someone who is qualified to work within a limited approach boundary.

liquefy

To change from a solid into a liquid. Arc flash can cause metals to liquefy.

lockout/tagout

A method of protecting employees from accidental machine startup. Lockout/tagout requires machines to be locked and labeled to notify employees when they are undergoing maintenance or other work.

maintenance

Any activity that contributes to the care and upkeep of machines or equipment. Maintenance approaches can involve monitoring equipment for problems or fixing a machine after it breaks down.

miles per hour

mph. A unit that indicates speed in the English system. Miles per hour is equal to the distance traveled in miles divided by the time spent traveling in hours.

motors

A machine that converts electrical energy into mechanical energy or motion. Motors contain several electrical conductors called windings.

National Electrical Code

NEC. The standard for minimum safe electrical installations in the United States. The National Electrical Code, also referred to as NFPA 70, is adopted in some form as law in all 50 states.

National Fire Protection Association

NFPA. An organization dedicated to preventing fires from electrical work. The National Fire Protection Association authors NFPA 70E, the electrical safety standard that includes arc flash safety standards.

neutral wire

The conductor that returns power back to its source and completes a circuit. The neutral wire is usually covered with white insulation.

NFPA

National Fire Protection Association. An organization dedicated to preventing fires from electrical work. The NFPA authors NFPA 70E, the electrical safety standard that includes arc flash safety standards.

NFPA 70

The standard for minimum safe electrical installations in the United States. NFPA 70, also referred to as the National Electrical Code, is adopted in some form as law in all 50 states.

NFPA 70E

The standard for electrical safety in the workplace. NFPA 70E is used by OSHA to provide work safety guidelines for those working with electricity.

NIOSH

National Institute for Occupational Safety and Health. An organization that promotes a productive workplace through safety and health research. NIOSH authors a small guide on arc flash safety.

non-conductive

Unable to act as a path for the flow of electricity. Non-conductive materials like rubber and leather provide insulation from electric currents.

Occupational Safety and Health Administration

OSHA. An organization that ensures safe, healthy working conditions by creating and enforcing standards. The Occupational Safety and Health Administration sets arc flash prevention standards.

overcurrent devices

A component that protects circuits from experiencing excessive current. Overcurrent devices open to interrupt current flow when current passes a set level.

pascals

Pa. A measurement of pressure in the metric system. Pascals can express the pressure generated by an arc blast.

personal protective equipment

PPE. Any of the various articles of clothing or safeguarding devices that employees wear to ensure their safety. Personal protective equipment for arc flash includes arc flash suits, non-conductive gloves and footwear, and face and eye protection.

pounds per square foot

psf. A measurement of pressure in the English system. Pounds per square foot can express the pressure generated by an arc blast.

PPE

Personal protective equipment. Any of the various articles of clothing or safeguarding devices that workers wear to ensure their safety. PPE for arc flash includes arc flash suits, non-conductive gloves and footwear, and face and eye protection.

pressure

The exertion of a mechanical force upon an object. Pressure from an arc blast can cause severe injuries.

preventive maintenance

Regularly scheduled service and upkeep performed while a machine or system is still in working order. Preventive maintenance can prolong equipment life and increase production.

restricted approach boundary

A border that defines the distance from an energized system at which an employee has an increased risk of electric shock. Employees must wear appropriate PPE and avoid contact with energized parts of electrical circuits when working within a restricted approach boundary.

safeguards

Any device, barrier, or process that protects an employee from being injured. Safeguards in electrical work include devices such as fences, enclosures, and lockout/tagout devices.

safety glasses

Protective eyewear with metal or plastic frames and impact-resistant lenses. Many safety glasses also have protective side shields.

safety goggles

Tight-fitting eye protection that completely covers the eyes, the sockets, and the surrounding facial area. Safety goggles offer protection from impact, sparks, dust, chips, and splashes.

second degree burn

A severe burn that affects the first and second layers of skin. Second degree burns cause blisters that affect the middle and outer layers of skin.

shock hazard

A circuit or electrical system component that is at risk of causing an electric shock to employees. Shock hazards can be detected through arc flash hazard analyses.

short circuit

A situation in which electricity fails to flow as intended through a circuit. Short circuits can damage circuits and even start fires.

sock hoods

A close-fitting arc-rated hood that covers the head and neck but not the eyes or nose. Sock hoods are also called balaclavas.

sound wave

The disturbance of matter caused by the movement of energy. Sound waves that result from arc blast can damage hearing.

switchboards

A freestanding assembly of panels with electrical meters, overcurrent devices, and other protection devices. Switchboards make overcurrent devices quickly and easily accessible to technicians.

thermal contact burns

A burn caused by fire or extreme heat. Thermal contact burns may result from arc flash events.

thermal energy

Energy created by or in the form of heat. Thermal energy generated by arc flash events can cause severe burns.

trip

To automatically open a circuit to prevent damage and injury. Tripped overcurrent devices prevent current from traveling through a circuit.

vaporize

To change from a liquid into a gas. Arc flash can cause metals to vaporize.

voltages

The electrical force or pressure that causes current to flow in a circuit. Voltage is measured in volts (V).

volts

V. A unit of measurement that indicates the amount of electrical pressure in a circuit. Electrical systems that run on 50 volts or more require arc flash risk assessments.

welding

A joining process that uses heat, pressure, or chemicals to permanently fuse materials together. Welding equipment generally includes electrical conductors and can lead to arc flash.