Working with transmission lines presents some unique hazards for lineworkers and utility personnel, but there are few general guidelines for working safely that should never be ignored. We encourage workers and supervisors to always follow best practices to ensure the safety of all workers involved.

Responsibilities of the Supervising Employee

When de-energizing pieces of the electrical infrastructure properly, OSHA requires that one person be in charge of the de-energized lines or equipment, and of disconnects that clear its energy supply. If a system operator (such as a dispatcher) is in charge, work crews must designate one member to be in charge of the clearance, and of the de-energizing steps. OSHA requires the supervising employee to take the necessary precautions to protect the crew from direct and induced energy sources.

This person must execute specific steps, in a specific order…

1. Request - Ask the system operator to de-energize a particular section of lines or equipment.
2. Open Switches - Identify, and open, all switches, jumpers, and other electrical sources that could feed the lines or equipment you’ll work on.
3. Lock/Tag - To prevent switches from reclosing, lock open all switches that could supply the lines or equipment they’re working on. Also, tag them. This requirement applies to manually, automatically, or remotely controlled switching devices.
4. Control - Also lock open, and tag, any disconnecting devices that could be operated by people outside the employer’s control, such as the general public.

The Single Crew Exception

OSHA provides a narrow exception from its tagging requirement if only one crew will be working on the lines or equipment; and if the employee in charge can see and access the disconnects, and has sole control over them. But workers shouldn’t be in a rush to skip tagging; workers can’t always know whether they’re the only crew working.

Network-Protector Exception

Workers are not required to tag network protectors when all of these conditions are met:

• The network protector will immediately trip open when a primary conductor is de-energized.

• Employees can’t manually force the network protector closed.

• Workers can manually override the network protector to keep it open.

• Breakers are set to one-shot, with no automatic recloser.

Once workers “have air” between lines or equipment and all electrical sources, the crew must then ensure three further precautions:

1. Obtain Clearance - The system operator can now give a clearance to the employee in charge. This formal step helps ensure that Control Center staff, and any other crews, will be aware that crews are working on normally live equipment.
2. Test for Zero Voltage - Test the lines and equipment they are about to work on, to verify that the implements are de-energized.
3. Install Temporary Protective Grounds - Install grounds, to protect the crew against hazardous differences in potential. When these grounds are in place, workers are now allowed to work the isolated lines and equipment as de-energized.

5 Steps Before Working Lines or Equipment as De-Energized

1. Requesting clearance should be the first step.
2. Open disconnecting devices before tagging.
3. Lock out/tag out after disconnecting, before voltage testing.
4. Voltage testing should follow lock out/tag out.
5. Grounding should be the last of these steps.

Releasing a Clearance

The person releasing a clearance must be the same person who earlier requested that clearance, unless he or she has transferred responsibility. The first step is to notify everyone working under this clearance that workers plan to release the clearance. Next, make sure that all crew members, and their tools and gear, are clear of the lines or equipment. Make sure the crew has removed all protective grounds they installed. Then report your progress to the system operator and release the clearance. Workers may not remove tags until you’ve released the clearance.