• Ammeter—An instrument for measuring the magnitude of electrical current. Portable test instruments are generally a clamp-around type device which has a digital or analog indication.
  • Audio and Visual Voltage Tester—A tester which provides an audio tone and visual indication when in close proximity to AC energized systems.
  • Circuit Breaker—A device designed to open and close a circuit by manual or electrical means. It is capable of clearing short circuit currents without damage when properly applied within its rating.
  • Competent Person—A trained person having sufficient technical knowledge and experience to complete an assigned task safely.
  •  Contactor—A device for repeatedly establishing and interrupting normal load current in an electric power circuit.
  • Current—Measure of electrical flow. Measured in Amps or Amperes.
  • De-energized—Free from any electrical potential.
  • E-2 Starter—A NEMA rated combination fuse and high-voltage contactor used on high-voltage circuits.
  • Electrical Room—Indoor electrical area containing high voltage and/or low voltage electrical equipment.
  • Electrolytic Cell Line Definitions

Cell Battery Voltage—The potential between the cell terminals created by the chemical reaction within a disconnected electrolytic cell.

Cell Bypass (Shorting) Switch—A permanently mounted switch that when closed carries the cell line current and allows the cell line process to continue when removing an electrolytic cell. The Cell Bypass Switch is mechanically interlocked with the Cell Isolating Switches.

Cell (electrolytic)—A tub and head assembly in which electrochemical reactions are created by applying DC current for the purpose of producing usable materials.

Cell Flexible Cables—conductors between the Cell Isolating (Disconnecting) Switch and the electrolytic cell termination posts.

 Cell Isolating (Disconnecting) Switch—A set of two switches that operate together to connect and/or disconnect a cell from the DC power of the cell line copper bus work. The Cell Isolating Switches are mechanically interlocked with the Cell Bypass Switch.

 Cell Line—An assembly of electrically interconnected electrolytic cells.

 Cell Line Working Zone (CLWZ)—The cell line working zone is the space envelope wherein operation or maintenance is normally performed on or in the vicinity of exposed energized surfaces of the electrolytic cell lines or their attachments.

Cell Voltage—The dc voltage between the positive (Anode) and negative (Cathode) buses supplying power to a single electrolytic cell.

De-energized—Applies to cell lines. A state of having no external source of dc power to the cell line. (CAUTION: the Cell Battery Voltage is still present.)

Energized—Applies to cell lines. Applying an external source of dc power to the cell line.

Grounded (Earthed)—Connected to ground (earth) or a conductor body that extends the ground (earth) connection.

Guarded—Covered, shielded, fenced, enclosed or otherwise protected by means of suitable covers, casings, barriers, rails, screens, mats, or platforms to remove the likelihood of approach or contact by persons or objects to a point of danger.

Insulated (electrically isolated)—Separated from other conducting surfaces by a dielectric substance or air space permanently offering a high resistance to the passage of current.

  Power Bus Compartment—A segregated section of a rectifier dedicated to housing the bus bar, SCRs, transformer connections, and other current carrying, exposed parts.

Rectifier—An assembly of electrical and electronic components used to convert alternating current (ac) to direct current (dc).

Safeguard—A precautionary measure or stipulation, or a technical contrivance to prevent accidents.

Safe Work Practices—The operating and maintenance procedures and controls written to reduce personnel hazards and minimize risk.

Energized—Electrically connected to a source of electrical energy.


  • Grounded or Earthed—Connected to the general mass of earth.
  • High Voltage—1001 volts and higher.
  • Industrial Electrical Equipment—Electrical equipment such as switchgear, motor control centers, power distribution centers, panel boards, circuit breakers, motors, transformers, etc., designed for use in an industrial environment, indoors and outdoors.
  • Insulated Tools—See Voltage rated tools.
  • Isolation—Free from electrical sources by means of a device or procedure that establishes a break in the electrical circuit.
  • Isolation Mechanism—The operating mechanism, device and/or procedure required to electrically isolate from the source of electrical energy, and allow the equipment to be physically locked in the safe position.
  • Low Voltage—Between 31 and 1000 volts.
  • On/Off (start/stop)—Normal control means to shutdown or startup an electrical device. Example: pushbutton, DCS, etc.
  • Physical Break—The withdrawing of a withdrawable electrical device, or the disassembly of a permanently connected assembly (bus bar link, cable termination, etc.) to provide electrical isolation.
  • Qualified Contractor—One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training from their employer to recognize and avoid the hazards involved.
  •  Qualified Person—One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training to recognize and avoid the hazards involved.
  • Fully Authorized—A competent person who is authorized to operate, perform electrical maintenance tasks and electrical system isolations as documented by the qualified level electrical safety awareness and aptitude training certificate. This authorization category is generally site specific.
  • Q-EL A technician or Engineer with additional training, qualifications and experience in Operating, Maintaining and Earthing/Grounding Electrical Systems. This is the highest level of electrical authorization.
  • Q-MA—Authorized to perform prescribed maintenance tasks on specified equipment.
  • Q-OP—Authorized to operate specified equipment.
  • Site Specific Arc Flash Assessment—Conducted by Electrical Engineering to determine the appropriate PPE and/or operating restrictions for operating and maintaining electrical equipment. The assessment uses the calculated incident energy level as a starting point and considers:

The equipment design.

The operating conditions.

The expected level of electrical expertise at a particular location.

The probability of an incident.

The equipment ownership (Air Products, customer, utility) and how that relates to the maintenance of the equipment in question.

The possibility of the higher rated PPE becoming a burden due to work practicality.

The industry recommendations.

As an example, given the same calculated incident energy levels, two similar pieces of equipment at different locations may result in different recommended PPE levels depending on the site specific assessment.


  • Switch Stick/Hot Stick—An insulated rod, tube, or pole used for the purpose of testing or operating equipment while it is energized, assumed to be energized, or in close proximity to other energized components. It allows the individual using this device to remain a safe distance away from the energized electric equipment.
  • Switchgear—Switching and interrupting devices, associated control, instrumentation, metering, protective and regulating devices, interconnections, supporting structures, and accessories, used primarily in the distribution of electrical energy.
  • Switchyard—Outdoor electrical areas containing electrical equipment. This may include exposed, uninsulated equipment.
  • Voltage—Measure of electrical potential. Measured in Volts.
  • Voltage Rated tools—Hand tools or devices that are designed to come in contact with energized equipment. Voltage level limits must be identified on the tool. These may also be referred to as insulated tools.
  • Voltmeter—An instrument for measuring the magnitude of potential difference.
  • Racking—Engaging or dis-engaging of an electrical device from a bus connection; for example, Circuit Breakers, Contactors, VT/PT, etc.


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