De-energizing Lines and Equipment for the Protection of Employees
It’s critical for workers to understand the process of de-energizing lines and equipment to hold them clear.
As with all articles in this series, it is important to start with the hazard. Electrical hazards are present when electrical systems are assumed to be de-energized but are not. It is important to remember that transmission and distribution (T&D) systems are different from other energy systems found in general industry and construction industry applications. Electric T&D systems are mostly located outdoors, meaning these lines and equipment are subject to re-energization by means other than normal energy sources. OSHA describes scenarios such as lightning striking a line and energizing a de-energized conductor, and unknown co-generation sources that can energize a line. Additionally, some de-energized T&D lines are subject to re-energization by induced voltage from nearby conductors or by contact with other energized sources of electrical energy. Also keep in mind that energy control devices often are remote from the work site and frequently are under the centralized control of a system operator.
OSHA requirements for the control of hazardous energy sources related to T&D systems can be found at 29 CFR 1910.269(m) and 1926.961, both of which are titled “Deenergizing lines and equipment for employee protection.” T&D organizations typically refer to these requirements as switching and tagging programs.
OSHA includes requirements for system operators, de-energizing lines and equipment, tagging, working as de-energized, re-energizing lines and equipment, and clearances. OSHA describes a clearance as the procedure used to de-energize lines and equipment and hold them clear for the protection of employees.
Now, let’s take a closer look at some of these requirements.
A system operator is defined as a qualified person designated to operate the system or its parts.
When a system operator is in control, they must assign control to one employee who will be in charge of a clearance. When no system operator is in control, one employee must be assigned to be in charge of the clearance and perform the functions of the system operator.
Typically, a system operator is a qualified person, located in a control room, who operates the system. Some systems are under the direction of a central system operator, and other systems, mostly smaller distribution installations, may not be under centralized control. Although these smaller utilities may not have a control room, it is important to remember that the function of a system operator is still required. The National Electrical Safety Code (ANSI C2) requires utilities to “keep informed of operating conditions affecting the safe and reliable operation of the system and to maintain a record showing operating changes.” This means organizations should develop an organized process to ensure system changes are documented and maintained for future field use. Although field employees should never rely solely on documentation but rather field verification, the documentation does remain an important communication method to alert employees of field changes.
De-energizing Lines and Equipment
The employee in charge of a clearance, typically referred to as the clearance holder, must make a request to the system operator to de-energize lines and equipment. OSHA does allow an exception to this rule when only one crew is working and the means of disconnection is accessible, visible and under the sole control of the employee in charge of the clearance.
OSHA requires that certain procedures be followed for de-energizing live parts at voltages over 50 volts if employees will be in contact with the parts during the course of work. The basic steps necessary for de-energizing electric circuits are the same regardless of voltage:
- First, the disconnecting means for the circuit must be opened. A visual opening should always be used as applicable.
- Second, a method of securing the disconnecting means from accidental closure must be used.
- Third, the circuit must be tested to ensure that it is de-energized.
- Fourth, measures such as grounding must be used to ensure that no hazardous voltage can be impressed on the circuit while employees are working.
According to OSHA, conductors and equipment that have not been de-energized as described above must be treated as energized.
Tags must be used to prohibit operation of the disconnecting means and to indicate that employees are at work. The purposes of a tag are to ensure all points of electrical potential are identified, to give information to field personnel concerning tag placement, and to ensure the switch or disconnector cannot be operated until authorization is granted for tag removal.
Tags must be used effectively and consistently whether the organization has one crew or thousands of crews.
Releasing a Clearance
Only the employee in charge who requested a clearance may release the clearance unless it has been transferred. No tags may be removed without the release of the associated clearance, and no re-energization may occur at any point of a disconnection until grounds have been removed, all crews have released their clearances, all employees are clear of the lines and all tags are moved from the point of operation.
T&D organizations have many unique issues that are not easily addressed in a traditional lockout/tagout program. It is important for utilities and utility contractors to identify these unique issues and to develop robust programs appropriate for the work applications.
To ensure worker safety and system reliability are maintained, remember that a fully developed and managed process to effectively de-energize lines and equipment must be reviewed regularly and updated as improvements are identified.
About the Authors: Pam Tompkins, CUSP, CSP, is president and CEO of SET Solutions LLC. She is a 40-year veteran of the electric utility industry, a founding member of the Utility Safety & Ops Leadership Network and presently serves on the USOLN executive board. Tompkins worked in the utility industry for over 20 years and has provided electric power safety consulting for the last 20 years. An OSHA-authorized instructor, she has supported utilities, contractors and other organizations operating electric power systems in designing and maintaining safety improvement methods and strategies for organizational excellence.
Matt Edmonds, CUSP, CIT, CHST, is vice president of SET Solutions LLC. A published author with over 15 years of safety management experience, he also is an OSHA-authorized instructor for general industry and construction standards. Edmonds provides specialty safety management services for electric power organizations throughout the U.S. He has been instrumental in the development of training courses designed for electric power organizations, including OSHA 10- and 30-hour courses and SET Solutions’ popular OSHA Electric Power Standards Simplified series.
About OSHA Electric Power Standards – Simplified: Topics in this series are derived from SET Solutions’ popular OSHA electric power course offered through the Incident Prevention Institute (https://ip-institute.com). The course is designed to help learners identify standard requirements and to offer practical ways to apply the standards.
Learn more on the iP Institute Podcast. Visit https://ip-institute.com/podcasts/#OSHA to listen now!