One of the most important steps in establishing an Electrically Safe Work Condition is verifying the absence of voltage. Opening a disconnect and applying lockout/tagout does not guarantee the equipment is safe. Backfeeds, stored energy, or improper isolation can still leave circuits energized.
Voltage testing must be performed by a qualified person trained in the use of the test instrument. The worker must understand the equipment, the maximum voltage present, and the hazards involved. Before testing, the circuit and energy source must be identified, and both shock and arc flash risk assessments must be performed. Proper personal protective equipment must be selected based on these conditions.
The test instrument must be properly rated for the environment and inspected before use. Test leads and probes must be in good condition.
A widely accepted method for verifying absence of voltage is the “live–dead–live” method. First, test the meter on a known live source to confirm it is working. Next, test the equipment, checking each exposed conductor phase-to-phase and phase-to-ground. Finally, return to the live source to confirm the meter is still functioning. Until absence of voltage is verified, the equipment must be treated as energized.
Proper working clearances, approach boundaries, and adequate lighting must also be maintained during testing. Verifying absence of voltage confirms that electrical energy has been effectively isolated and that an Electrically Safe Work Condition has been established.
Contributed by Charles Rayder, CESCP, CHST
Five Star Electric Safety Director
One of the most important steps in establishing an Electrically Safe Work Condition is verifying the absence of voltage. Opening a disconnect and applying lockout/tagout does not guarantee the equipment is safe. Backfeeds, stored energy, or improper isolation can still leave circuits energized.
Voltage testing must be performed by a qualified person trained in the use of the test instrument. The worker must understand the equipment, the maximum voltage present, and the hazards involved. Before testing, the circuit and energy source must be identified, and both shock and arc flash risk assessments must be performed. Proper personal protective equipment must be selected based on these conditions.
The test instrument must be properly rated for the environment and inspected before use. Test leads and probes must be in good condition.
A widely accepted method for verifying absence of voltage is the “live–dead–live” method. First, test the meter on a known live source to confirm it is working. Next, test the equipment, checking each exposed conductor phase-to-phase and phase-to-ground. Finally, return to the live source to confirm the meter is still functioning. Until absence of voltage is verified, the equipment must be treated as energized.
Proper working clearances, approach boundaries, and adequate lighting must also be maintained during testing. Verifying absence of voltage confirms that electrical energy has been effectively isolated and that an Electrically Safe Work Condition has been established.
Contributed by Charles Rayder, CESCP, CHST
Five Star Electric Safety Director