Affected Employee - Non-qualified employee trained to work on affected piece of machinery or equipment, but not on electrical devices or energized parts such as a machine operator, production line worker or cleaning maintenance worker.


ARC Flash/Blast - An arc flash is the light and heat energy from ranging from far infrared to ultraviolet that is generated from an arc fault event due the flow of electrical current outside of its normal path. Arc flash may also be referred to as "flashover". The light energy is sufficient enough to ignite combustible materials, burn unprotected skin and cause permanent blindness. The arc blast of the arc fault event is the subsequent pressure wave created by the rapid heating of the conductive materials causing them to melt, vaporize, and expand the surrounding air.


Arc Rated (AR) - Arc Rating measures the insulating properties if Flame Resistant (FR) fabric/materials to Arc Flash. Arc Rated PPE is Flame Resistant PPE that has been tested to arc flash conditions with sensors measuring the heat transfer through the fabric. Calculations determine the energy transfer that would probably result in a 2nd degree burn through the fabric 50% of the time and expressed as a number in calories/cm2. Note that all clothing that is Arc Rated is also Flame Resistant but not all FR PPE is arc rated. The label should indicate that the garment complies with the applicable American Society of Testing and Materials standard. Note: The higher the Arc Rating value, the greater the protection.


Balaclava (Sock Hood) - An arc-rated hood made of fire resistant material that helps protects the neck and head. It has an opening for the for the eyes and nose facial area which is therefore not protected by the hood.


Barricades/Barriers - A physical obstruction such as tapes, cones, or A-frame type wood or metal structures intended to provide a warning about and to limit access to a hazardous area. A physical obstruction which is intended to prevent contact with energized lines or equipment or to prevent unauthorized access to a work area.


Circuit - A complete path for the flow of current.


Circuit Breaker - An overcurrent protection device that automatically shuts off the current in a circuit if an overload occurs.


Current Limiting Fuse - A type of fuse that very quickly introduces a high level of resistance once the device's current responsive element is melted by current flow as specified by the fuse's current limiting range, thus reducing the current's magnitude/duration and results in current fault interruption.


Conductor - Any material that has a low level of resistance, allowing the flow of electrons. This may include metals such as aluminum, copper and steel, to name a few, as well as materials with high moisture content, such as water, concrete and even air. Note: Distilled (de-ionized water itself is a good insulator; however, water that has any dissolved substances in it becomes conductive, even with a small amount of material creating an ion imbalance.


De-energized State - A device is in a de-energized state when disconnected from a source of electrical current and free of potential or stored electrical energy. Note that even though an electrical device may have had the power source removed; there may be residual energy present. Only a qualified worker with proper electrical training and equipment is qualified to determine the status of a device.


Electricity - The flow of energy in the form of electrons as through a conductor or across the gap between conductors.


Energized State - A device is in a energized state when connected to an source of electrical current, or stored (potential) electrical energy.


Energy Control and Power Lockout (ECPL) - Also referred to as "Lockout/Tagout" or LOTO - these are specific practices and procedures to follow to ensure employee safety when working on machinery to prevent accidental or unexpected energizing or start-up. An individual disconnects the equipment from its energy sources and any individual authorized to work on the machinery/equipment places their own lock or tag on the energy isolating device. The equipment is then verified that the machine/equipment is de-energized. This lesson may refer to ECPL but does not cover the subject.


Energy Isolating Device - A physical device that prevents the transmission or release of energy, including, but not limited to, the following: a manually operated electric circuit breaker, a disconnect switch, a manually operated switch, a slide gate, a slip blind, a line valve, blocks, and any similar device with a visible indication of the position of the device. (Push buttons, selector switches, and other control-circuit-type devices are not energy isolating devices.)


Fire Resistant (FR) - Typically refers to clothing that is flame resistant or flame-retardant-treated, when exposed to flames or electric arcs, would not increase the extent of injury that would be sustained by the employee. First, FR resists ignition from the initial arc flash, secondly FR insulates the wearer from thermal injury.


Ground - A large conducting body (such as the earth) used as a common return for an electric circuit and as an arbitrary zero of potential.


Ground Fault - A loss of current from a circuit to a ground connection.


Ground Fault Interruption Device (GFID) - A device that functions to de-energize a circuit or portion of a circuit for the protection of personnel within an established period of time when the current to ground exceeds a predetermined value that is less than required to operate the overcurrent protection device of the supply circuit.


Guarding - The covering or barrier that separates you from live electrical parts.


Hazard - A source of possible injury or damage to health.


Hazard Risk Category (HRC) - A NFPA 70E 2012 rating system used to determine the AR of PPE for a specific task. There are four categories listed from HRC 1 to HRC 4. Note: NFPA 70E 2015 has replaced HRC with "arc rated PPE category" and eliminated the HRC 0 level.


Insulator - Any material with a high level of resistance that prevents the flow of electrons such as rubber, plastic, glass, etc., the opposite of a conductor. Note: Air space can be considered a type of insulation.


Insulated Tools - Tools or equipment designed to provide insulation from an energized part or conductor. It may have conductive parts and be coated or covered by a dielectric material, or it may be composed entirely of insulating materials. Insulated industrial hand tools are typically stamped on the handle with an emblem (a double triangle) and a voltage rating. Such tools must be ASTM certified.


Insulating Protective Equipment (IPE) - Such as line hoses, rubber hoods, rubber blankets, and insulating live-line tools (for example, hotsticks, switchsticks, or shotgun sticks) for protection. However, since IPE is not worn, it is technically not considered to be PPE.


Overcurrent - Any current that exceeds the safety rated current of equipment or the ampacity of a conductor. It may result from overload, short circuit or ground fault.


Overcurrent Protection Device (OCPD) - A device that shuts off the current in a circuit when it reaches a certain level.


Overload - A current load greater than the load for which the system or mechanism was intended. A fault, such as a short circuit or ground fault, is not an overload.


Panel Board - (also panelboard or distribution board) A cabinet with an access door(s) which contains electrical devices such as, circuit breakers uses, short-circuit protection devices, usually mounted in or on a wall or on the device it is associated with.


Personal Protective Equipment (PPE) - Clothing or other devices usually worn to protect the user from harm in the workplace. In the case of electrical hazards, protecting the user from the effects of arc flash /blast hazards.


Qualified Person - NFPA 70E 2015, a national standard, addresses the standards for electrical safety in the workplace. It defines a "Qualified Person" as: "One who has demonstrated skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to identify and avoid the hazards involved." 


Rated Voltage - The maximum voltage at which an electric component can operate for extended periods without undue degradation or safety hazard.


Risk - A combination of the likelihood of occurrence of injury or damage to health and the severity of injury or damage to health that results from a hazard. (NFPA 70E 2015)


Risk Assessment - An overall process that identifies hazards, estimates the potential severity of injury or damage to health, estimates the likelihood of occurrence of injury or damage to health, and determines if protective measures are required. Informational Note: As used in this standard, arc flash risk assessment and shock risk assessment are types of risk assessments. (NFPA 70E 2015)

Also: A combination of the likelihood of occurrence of injury or damage to health and the severity of injury or damage to health that results from a hazard.


Short Circuit - Also referred to as a "short", it is a connection that allows current to flow through a low-resistance, unintended path between two points in an electrical circuit.


Switchboard - A large single panel, frame, or assembly of panels having switches, overcurrent, and other protective devices, buses, and usually instruments mounted on the face or back or both. Switchboards are generally accessible from the rear and from the front and are not intended to be installed in cabinets.


Switchgear - Electrical supply disconnect equipment consisting of switches and circuit protection devices combined with control, metering and regulating devices in a power system. It is used to isolate and de-energize electrical equipment downstream for accessibility and to clear faults.


V-rated - Line-to line voltage at location of where work is to be performed tested and rated for equipment such as gloves, tools used for near or direct contact of electrical equipment. Must meet ASTM certifications.


Figure 1: Arc Flash/Blast



Figure 2: Balaclava Nomex Fire Resistant Head Covering



Figure 3: Current Limiting Fuses in AIMSS



Figure 4: Energy Control/Power Lockout (LOTO)


Figure 5: Electrical Guarding



Figure 6: Insulated Tool



Figure 7: Electrical Cabinet Panel Board



Figure 8: Rated Voltage



Figure 9: Switchboards



Figure 10: Switchgear