Even though testing for the absence of voltage is a pretty straightforward process, it needs to be conducted with care in order to avoid shock, injury and even death. Follow these recommended steps prior to testing for voltage.
1. Verify your test instrument is reliably reading voltage
NFPA 70E requires that the "operation of the test instrument be verified on any known voltage source before and after an absence of voltage test is performed." In other words, connect your meter to an outlet or a proving unit whose voltage you already know and make sure your meter reads the correct voltage. If it doesn't, then you can't rely on that meter to tell you whether voltage is present and work must stop until a correctly-operating test instrument is used to verify the absence of voltage.
2. Inspect your test instrument
- Are there any obvious defects in the case or meter element?
- Does the selector switch turn smoothly without binding?
- Do the functions change properly when the selector switch is operated?
- Does the test instrument have the correct CAT rating for the part of the electrical system it is being used on?
- Does the display function properly? Are the digits broken or do they fade in and out?
3. Inspect your test leads
Lead damage can be hard to detect. Test leads can be easily damaged during use (or improper storage), so best safety practice is to replace them annually. They are expendable and low cost. Here are some questions to ask during the test:
- Are there any signs of damage, such as cuts or breaks in the insulation, melted or discoloration of the insulation, or crushing of the test lead?
- Are the probe ends straight and undamaged?
- Are the probe ends tight?
Caution: Never store the test leads wrapped around the test instrument.
4. Wear proper PPE
Always wear PPE based on NFPA 70E recommendations, until you have verified the equipment is in an electrically-safe work condition. The greater the electrical hazard, the higher the personal protective equipment arc-rating must be to withstand an arc-flash incident. PPE that might be required includes:
- Safety glasses.
- Insulated tools.
- Insulated gloves and leather protector gloves.
- Ear plugs or other hearing protection that is covered by arc-rated PPE.
- Face shield/hood.
- Arc-resistant clothing.
5. Follow lockout/tagout procedures
NFPA 70E requires those working on exposed conductors and circuit components operating at 50 volts or more to use lockout/tagout devices and procedures and be properly trained. The following steps make up part of the logout/tagout process:
- Apply temporary protective grounds when necessary.
- Watch for unguarded conductors that are still energized.
- Be certain of a tight clean connection at the point of grounding.
- Always follow the lockout/tagout procedure for the specific equipment being isolated.
Once you've gone through the Lockout/Tagout process, are wearing the proper PPE and you have the appropriate (and inspected) voltage test instruments, you're ready for the absence of voltage test.
For more information on Electrical Safety, see our online course available at the Fluke eLearning Center.