High Voltage Safety 255

alternating current

AC. Electricity that reverses direction at regularly recurring intervals of time. Alternating current alternates 60 times per second, or 60 hertz (Hz), in the United States.

American National Standards Institute

ANSI. A private, non-profit organization that administers and coordinates voluntary standards and systems in the United States. The American National Standards Institute provides a process for industry groups to create and publish the specifications for some PPE.

approach boundaries

A border that marks how closely an employee may approach a location that is susceptible to hazards. Approach boundaries for electrical work include the limited approach boundary, the restricted approach boundary, and the arc flash boundary.

arc blast

The burst of light, heat, and pressure that accompanies arc flash. Arc blast exposure can cause serious physical injuries and permanent hearing and vision damage.

arc flash

An electrical explosion caused when an electric current travels through the air unintentionally. Arc flash releases intense light, heat, and energy that can cause potentially serious injuries to anyone nearby.

arc flash boundary

A border that defines the distance from an energized system at which an employee may experience second-degree burns if an arc flash occurs. When working inside an arc flash boundary, qualified employees must wear arc-rated PPE.

arc flash hood

A type of loose-fitting arc-rated PPE that covers the head and neck but not the eyes or nose. An arc flash hood is typically part of an arc flash suit.

arc flash risk assessment

A process used to analyze the potential for a specific electrical system or piece of electrical equipment to produce an arc flash event. 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

An arc-rated clothing system that covers the entire body, except for the hands and feet. Arc flash suits must be worn inside arc flash boundaries.

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 must be displayed on the PPE.

ASTM International

An organization that publishes standards for a broad range of materials, including rubber. ASTM International, formerly known as the American Society for Testing and Materials, publishes standards and labeling requirements for rubber insulating gloves and sleeves.

batteries

A device that converts chemical energy into electrical energy. Batteries are used to store and transmit energy.

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.

capacitors

A device used to store an electric charge. A capacitor consists of one or more pairs of conductors separated by an insulator.

cardiac arrest

The sudden temporary or permanent stopping of the heart. Cardiac arrest may occur if a person experiences electric shock.

Class 00 gloves

The lowest acceptable level of rubber insulating gloves for energized electrical work. Class 00 gloves can be used with up to 500 V of AC or 750 V of DC.

Class 4 gloves

The highest available level of rubber insulating gloves for energized electrical work. Class 4 gloves can be used with up to 36,000 V of AC or 54,000 V of DC.

Class E hard hats

A type of insulated hard hat that can withstand up to 20,000 V. Class E hard hats are one of the two types of hard hats approved by ANSI for electrical work.

Class G hard hats

A type of insulated hard hat that can withstand up to 2,200 V. Class G hard hats are one of the two types of hard hats approved by ANSI for electrical work.

conductor

A material that allows electricity to flow easily. Common conductors include metals and water.

Department of Energy

DOE. A department of the U.S. federal government that oversees energy production and safety. The Department of Energy defines high voltage as electricity above 600 V.

dielectric boots

A type of insulating rubber footwear that protects the feet and lower legs from electric shock. Dielectric boots may be worn by themselves or over other footwear.

dielectric breakdown

A process that occurs when an electrically insulating material is subjected to high voltage electricity and suddenly becomes an electrically conductive material. Dielectric breakdown occurs at different voltages depending on the material.

dielectric strength

The voltage at which the insulating qualities of a material break down. Dielectric strength is an important consideration for selecting high voltage PPE.

direct current

DC. Electricity that flows in one direction. Direct current does not reverse the direction of flow.

disconnect switches

Any device that is used to separate an electrical circuit from its supply of electrical energy. When using a disconnect switch, operators should visually verify that it is in the fully disconnected position before proceeding with electrical work.

earmuffs

A protective device that consists of two ear coverings connected by a band. Earmuffs protect hearing and prevent debris from entering the ear.

earplugs

A protective device that is inserted into the ear. Earplugs prevent hearing damage.

electric arc

The area in which electricity passes through the air from one conductor to another. Electric arcs produce extreme heat and light and can cause serious injuries.

electric current

The flow of electricity through a circuit. Stronger electric currents are more likely to cause serious injuries.

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 high voltage electric shocks and arc flash events.

electrical circuits

A complete path for electrical current that includes various devices. An electrical circuit usually includes a source, path, load, and control.

electrically safe work condition

ESWC. A state in which an electrical circuit and all of its components have been de-energized, locked and tagged out, tested, and grounded, if necessary. NFPA 70E requires employees to establish electrically safe work conditions before conducting most electrical work.

electricity

Energy created by the movement of electrons. Electricity can be converted into light, heat, or motion.

energized electrical work permit

A document that must be prepared before starting energized electrical work. Energized electrical work permits must include several required elements as outlined in NFPA 70E.

face shields

A rigid, transparent plastic sheet that protects the face and eyes from debris and sparks. Some face shields also protect users from the intense light of an arc flash.

grounding

A means of providing a safe alternate path for electricity in case it strays from its intended path. Grounding protects the electrical system and substantially reduces the risk of electric shock.

hard hats

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.

high voltage electricity

Electricity with enough potential energy to cause serious injuries to people and serious damage to equipment. High voltage electricity may be defined as electricity above 50 V, 600 V, or 1000 V, depending on the regulatory standard in use.

hydraulic cylinders

An actuator that converts energy from pressurized liquid into linear mechanical energy. Hydraulic cylinders often perform repeated back-and-forth motions.

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.

insulator

A material that is non-conductive and prevents the flow of electricity. Common insulators include plastic, glass, and rubber.

International Electrotechnical Commission

IEC. An international organization that prepares and publishes standards for electrical, electronic, and related technologies. The International Electrotechnical Commission defines high voltage as electricity above 1000 V.

job briefing

A meeting in which supervisors and employees prepare for an upcoming task by reviewing job duties, risks, safety measures, and other important information. Evidence of a job briefing is a required part of an energized electrical work permit.

limited approach boundary

A border that defines the distance from an energized system at which employees are at risk of electric shock. To work within a limited approach boundary, employees must be qualified or directly supervised by a qualified employee.

lockout/tagout

LOTO. A method of protecting employees from accidental machine startup by locking and labeling machines that are undergoing maintenance or other work. Lockout/tagout renders a machine inoperable and is an essential safety practice.

mil

A unit of length measurement in the English system. One mil is equal to 0.001 of an inch.

millimeter

mm. A unit of length measurement in the metric system. One millimeter is equal to 0.039 inches.

National Electrical Code

NEC. The standard for minimum safe electrical installations in the United States. The National Electrical Code is published by the National Fire Protection Association (NFPA).

National Fire Protection Association

NFPA. A non-profit organization that maintains standards for public safety and fire prevention. The National Fire Protection Association publishes the National Electrical Code and NFPA 70E.

nerve damage

Impairment of one or more nerves in the body. Nerve damage can cause long-term pain, tingling, numbness, or muscle weakness in affected body parts.

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.

Occupational Safety and Health Administration

OSHA. A government agency under the U.S. Department of Labor that sets the standards for working conditions in the United States. The Occupational Safety and Health Administration ensures that employees work in safe and healthy environments.

OSHA

Occupational Safety and Health Administration. A government agency under the U.S. Department of Labor that sets the standards for working conditions in the United States. OSHA ensures that employees work in safe and healthy environments.

personal protective equipment

PPE. Any clothing or device worn to minimize exposure to hazards and prevent injury. Personal protective equipment for high voltage electricity may include insulated hard hats, insulated gloves, and insulated boots.

pliers

A pincer-shaped tool with flat gripping surfaces. Pliers are used to hold objects or bend wire.

PPE

Personal protective equipment. Any clothing or device worn to minimize exposure to hazards and prevent injury. PPE for high voltage electricity may include insulated hard hats, insulated gloves, and insulated boots.

qualified employees

An employee who is trained to perform electrical work. Qualified employees receive training specific to their job duties as well as advanced training on electrical hazards.

respiratory paralysis

Loss or impairment of the use of the respiratory organs. Respiratory paralysis can result from electric shock and prevents a person from breathing.

restricted approach boundary

A border that defines the distance from an energized system at which an employee has an increased risk of electric shock. To work within a restricted approach boundary, employees must be qualified and wear appropriate PPE.

risk assessments

A documented process that an organization uses to evaluate and plan for possible risks. Risk assessments are necessary for electrical work and many other hazardous activities.

safety officer

A professional who plans, implements, and oversees safety procedures in the workplace. Safety officers ensure that workplaces comply with safety laws and regulations.

screwdrivers

A hand tool used to tighten and loosen screws. Screwdrivers have a handle on one end and a blade that fits into the head of screws on the other.

second-degree burns

An injury caused by exposure to extreme heat that affects the first and second layers of the skin. A second-degree burn causes blistering and sometimes scarring.

shock risk assessment

A process used to analyze the potential for a specific electrical system or piece of electrical equipment to deliver an electric shock. During a shock risk assessment, a qualified employee calculates approach boundaries and identifies appropriate safety measures.

springs

A flexible device made of coiled material that yields under force and returns to its original shape when the force is removed. Springs are used in many mechanical systems to store and transfer energy.

Table 130.4(E)(a)

A table in NFPA 70E that provides distances for limited and restricted approach boundaries based on the voltage and type of electrical equipment. Table 130.4(E)(a) covers alternating current systems.

Table 130.4(E)(b)

A table in NFPA 70E that provides distances for limited and restricted approach boundaries based on the voltage and type of electrical equipment. Table 130.4(E)(b) covers direct current systems.

Table 130.5(C)

A table in NFPA 70E that estimates the likelihood of an arc flash event based on the type and voltage of electrical equipment. Table 130.5(C) estimates arc flash risk for equipment in both normal and abnormal operating conditions.

Table 130.7(C)(15)(a)

A table in NFPA 70E that provides distances for arc flash boundaries and recommended arc ratings for PPE based on the type and voltage of equipment. Table 130.7(C)(15)(a) covers alternating current systems.

Table 130.7(C)(15)(b)

A table in NFPA 70E that provides distances for arc flash boundaries and recommended arc ratings for PPE based on the type and voltage of equipment. Table 130.7(C)(15)(b) covers direct current systems.

third-degree burns

An injury caused by exposure to extreme heat that affects the first, second, and third layers of the skin, as well as tissue below the skin. A third-degree burn causes permanent scarring and may require skin grafts.

unqualified employees

An employee who is not authorized to perform electrical work but has been trained on basic electrical safety. Unqualified employees may work near high voltage electrical equipment but may not touch or directly approach it.

utility companies

An entity recognized by governmental law that installs, operates, and maintains equipment that supplies basic amenities, such as water or electricity. Electrical and communications utility companies are not covered under the scope of the NEC or NFPA 70E.

ventricular fibrillation

Rapid and ineffective heartbeats. Ventricular fibrillation can be caused by electric shock and may lead to death within minutes if a defibrillator is not used.

visible blade disconnect switch

A disconnect switch that uses moveable metal blades to control when a circuit is connected to its source of electrical energy. Visible blade disconnect switches allow operators to easily visually verify that a circuit has been isolated from electrical current.

voltage

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

voltmeter

A device that measures the voltage of an electrical circuit. Voltmeters can be used to verify the absence of voltage when establishing an ESWC.

volts

V. A unit of measurement that indicates the amount of electrical force or pressure in a circuit. Volts measure voltage, which is also known as electromotive force.

wire strippers

A hand-held device used to remove electrical insulation from wires. Wire strippers have blades with notches designed to cut through insulation while leaving wires intact.