EWT - General Concepts

To ensure the safety of everyone on the job site, lineworkers need to know specific terms to make sure other workers understand what they’re talking about.

Key Terms Every Lineworker Must Know

Energized
Electrically connected to a source of potential difference, or electrically charged so as to have a potential significantly different from that of earth in the vicinity.

Fault Current
The current that can flow in a circuit as a result of an undesired short circuit.

Interlock
An interlock is an engineered safety mechanism designed to prevent accidental switching of electric circuits. These safety devices can prevent interruption of service, as well as energizing.

De-Energized
Free from any electrical connection to a source of potential difference and from electric charge, and, or, not having a potential different from that of the earth. The term is used only with reference to current-carrying parts, which are energized (alive) during routine operations.

Nominal Voltage
The nominal voltage of a system or circuit is the value assigned to a system or circuit of a given voltage class for the purpose of convenient designation.

Most Common Electrical Equipment

• Buses
• Capacitor Banks
• Circuit Breakers
• Distribution Lines
• Fuses
• Meters
• Monitoring Equipment
• Pin Insulator
• Post Insulator
• Recloser
• Relays
• Sectionalizers

Line Work Safety Policies and Processes

Safety Devices: Engineered safety mechanisms designed to prevent accidental switching of electric circuits. These safety devices can prevent interruption of service, as well as energizing.

Existing Conditions: Existing conditions related to the safety of work to be performed should be determined before work on or near electric lines or equipment begins. Such conditions include, but are not limited to: nominal voltages of lines and equipment; maximum switching transient voltages; presence of hazardous induced voltages; presence and condition of protective grounds and equipment grounding conductors; condition of poles, environmental conditions relative to safety; locations of circuits and equipment, including power and communication lines, and fire protective signaling circuits.

Handling Emergencies: High winds, ice storms, fires, lightning, vehicle accidents, may each produce a situation where service is lost to customers. Depending on weather conditions the emergency may not end with a downed line. As a member of a repair crew, you must follow the company procedures exactly to avoid becoming part of the emergency. Practicing scenarios without the severe weather conditions will build your skill level and confidence.

Lightning: Lightning flashes are currents of electricity flowing from one cloud to another or between the cloud and earth. Overhead lines can have charges of electricity induced on them when charged clouds pass over them. Induced charges trapped on electric circuits can create abnormal voltages on the transmission and distribution lines when lightning strokes travel to ground, discharging the clouds. The abnormal voltages placed on the line will travel along the line until dissipated by surge arrestor operation, attenuation, and, or, leakage or by failure of insulators, transformers, or other apparatus connected to the line.

Determining Voltage On Equipment: Before any ground is installed, lines and equipment should be tested and found absent of nominal voltage, unless a previously installed ground is present. Before any employee uses the” live-line bare-hand” technique on energized, high-voltage conductors or parts, the following information shall be ascertained:

• The nominal voltage rating of the circuit on which the work is to be performed.
• The minimum approach distances to ground of lines and other energized parts on which work is to be performed; and before an employee climbs, enters, or works around any tree, a determination shall be made of the nominal voltage of electric power lines posing a hazard to employees.

Lockout/Tagout: Companies are required to have a lockout/tagout system in place to standardize how equipment is isolated for maintenance. Locks are used to physically prevent the operation of valves, electrical breakers, and other energy controlling devices. Locks are the preferred method of isolating systems and equipment. Tags may be used instead of a lock as long as there is some way to provide the same level of safety that a lock would provide.