Breaker testing and maintenance can expose personnel to many types of hazards. Mitigating them can be achieved in various ways. First, it must be verified that the personnel are qualified to perform the required tasks. The person doing the work must recognize and understand the hazards that may be encountered while performing the tasks.
To better understand the many hazards involved with testing and maintenance of breakers, let’s look at the sources that contribute to each hazard and consider ways to mitigate the risk.
PREPARE FOR THE JOB
Conduct Job Prep and Pre-Job Brief
Locate and review all service bulletins, maintenance documents, and manuals before beginning work.
Perform a pre-job brief with everyone who can affect the work or could be affected by the work on-site.
Recognize Hazards
Human error is simply when a person (or persons) makes a mistake.
Checklists are a great way to engage the mind and avoid mistakes. To help prevent human error, follow a procedure or checklist while performing any task. If one doesn’t exist, create one.
Mistaken identity of equipment is a common cause of mistakes and accidents due to inaccurate labeling and incorrect one-line diagrams, etc. Equipment nomenclature must be verified and re-verified upon approaching a piece of equipment. Perform a self-check and a peer-check to ensure that the task is being performed on the correct equipment.
Select Personal Protective Equipment
Before beginning work, select the appropriate personal protective equipment (PPE). The selection must be based on NFPA, OSHA, or CSA regulations for the class of breaker to be serviced. These regulations indicate the level of protection required to prevent electrical shock and protect personnel from an arc-flash.
Note that the information will be based on the known values of the short circuit current, the clearing time in cycles, and the minimum working distance. If those factors are unknown, more information must be gathered prior to performing the work to ensure personnel safety.
Isolate the Equipment
We often work around equipment that looks the same as other equipment.
Identify and flag the equipment being worked on to mitigate the risk of human error. Flagging can also be used to indicate a component that is not operating as expected, even when it is not visually apparent that it is not functioning normally. Flagging can take many forms, including signage, tags, and labels, depending upon the company or client’s policy and procedures.
Barricade off a safe work zone to prevent other workers from inadvertently entering the work area. This ensures maintenance and testing are conducted in an area under the control of the people performing the work.
CONTROL ENERGY
Failure to properly perform lockout and/or tagout (LOTO) contributes to many injuries when performing maintenance on breakers.
Electrical Energy
Controlling the electrical energy of a breaker is the first and most obvious hazardous energy source that can cause injury.
- Electrically de-energize the breaker.Ensure the breaker is disconnected from all sources of power.
- Once de-energized, verify that the breaker is at a zero-energy state using the manufacturer’s approved method.
- Test the measuring deviceagainst a known source, then check for zero energy on the de-energized equipment, and then test the detection equipment against a known source again. This will verify that the test device was functioning properly during the check. Testing for voltage requires its own level of personal protective equipment (PPE) depending upon the voltage and the test procedure, following NFPA, OSHA, and/or CSA requirements.
- Connect grounds where and if applicable. Refer to OSHA 29 CFR 1910.269, NFPA 70E Section 120.6, or CSA for specific guidance on grounding locations and ground sizing required for the task, and follow the manufacturer’s suggested practices.Personal protective safety grounds should be utilized when the equipment could contact energized components or when induced voltages or stored electrical energy exist.
- Tag out the equipment and notify all personnel in the work area.
Other Energy Sources
Electrical energy isn’t the only energy that requires control and LOTO.
Breakers contain a large amount of mechanical energy. This energy must be dissipated before servicing to prevent serious injury. Once the breaker’s mechanical energy has been discharged, it is also advisable to lock out and tag out the charging mechanism if feasible. Ensure that remote operating handles are tagged in a local or manual mode. This will prevent someone from inadvertently operating the breaker.
Gravity (potential energy) must also be controlled. The sheer size and weight of larger breakers make them difficult to rack in and out or to maneuver around. Mechanical lifting devices may be necessary to move the breaker to an area where it can be serviced. This type of energy does not necessarily require lockout/tagout, but it is an important hazard to consider.
Be aware of pressurized equipment or vessels. If pressurized equipment/vessel requires access, ensure the unit is depressurized, and the source of the pressure is disabled. The source of the gas or pressure must also be locked out/tagged out.
OTHER HAZARDS
Chemicals
Chemicals can be a hazard when maintaining various types of breakers. Sulfur hexafluoride (SF6) gas is used as an insulator in some applications, and care must be taken with damaged breakers that exhibit arcing, which can form a byproduct of sulfur pentafluoride, an extremely toxic gas. Additionally, SF6 is denser than air, so it will displace oxygen in lower-lying areas, similarly to carbon monoxide. Ventilation must be used if the gas may become trapped.
Lubricants and Cleaners
Some lubricants and cleaners pose a respiratory and skin irritant hazard if used in enclosed areas or on bare skin. Knowledge of the chemicals being used, reading the label, and checking the safety data sheet is advised to identify any potential health effects. When using some cleaners, personal protective equipment such as nitrile gloves, safety glasses, a face shield, and respiratory protection may be necessary.
Asbestos
Asbestos may be a hazard in some older breakers. Learn to properly identify its presence or the equipment that may have contained it. Do not handle or disturb asbestos unless you are properly trained.
CONCLUSION
When performing maintenance and testing on circuit breakers, we must recognize and take precautionary actions to avoid hazards.
- Gather and review all applicable service advisories, bulletins, manuals, and maintenance documents for the equipment being serviced.
- Perform a pre-job briefing.
- Utilize all appropriate PPE for the task.
- Use flagging and barricades.
- Use peer-checking and self-checking to prevent mistakes.
- De-energize, verify zero energy, and lockout and/or tagout the equipment.
- Install grounds where applicable.
- Utilize written procedures to ensure a step is not skipped or missed.
- Be familiar with the chemicals used and associated hazards.
Following these steps can lead to a safer work environment while performing maintenance and testing of breakers.
Paul Chamberlain has been the Safety Manager for Asplundh Electrical Testing, LLC (formerly American Electrical Testing Co., LLC), a subsidiary of Asplundh Engineering Services, LLC since 2009. He has been in the safety field since 1998, working for various companies and industries. Chamberlain received a BS from the Massachusetts Maritime Academy.