Tragic Event That Could Have Been Avoided
De-energized does not equal safe
NFPA 70E requires in article and section120.5 that workers complete an 8-step process before they can remove PPE and work safely on electrical equipment. Skipping any of these steps can have grave consequences. There is a common misunderstanding by electrical workers that once equipment is de-energized it is safe to work on. De-energized does not equal safe.
Try this case study
Reveiw the 8-steps of Establishing and Verifying an Electrically Safe Work Condition below as described in NFPA 70E 120.5. Then watch the video below.
- Can you identify the step(s) in the process that the worker performed correctly?
- Which step(s) did he skip?
- Had he completed the entire process as required would he have lost his life?
NFPA 70E 120.5 Process for Establishing and Verifying an Electrically Safe Work Condition.
- Determine all possible sources of electrical supply to the specific equipment. Check applicable up-to-date drawings, diagrams, and identification tags.
- After properly interrupting the load current, open the disconnecting device(s) for each source.
- Wherever possible, visually verify that all blades of the disconnecting devices are fully open or that drawout-type circuit breakers are withdrawn to the fully disconnected position.
- Release stored electrical energy.
- Release or block stored mechanical energy.
- Apply lockout/tagout devices in accordance with a documented and established procedure.
- Use an adequately rated portable test instrument to test each phase conductor or circuit part to test for the absence of voltage
- Ground all circuit parts where the possibility of induced voltages or stored electrical energy exists
Notice that the worker does identify the breaker that he would need to open to isolate the panel he will be working in using a drawing. This is step 1.
He opens the breaker this is step 2.
Step 3 would not be required because a molded case circuit breaker cannot be visually verified. This is what NFPA 70E refers to in step 3 as "Wherever possible".
Steps 4 and 5 were also not required. It does not appear that there were any stored electrical or mechanical energies were present.
He applies a lock and tag this is step 6.
What went wrong?
Unfortunately the wires feeding the panel he was working on had been moved to another breaker. The drawing had not been revised to indicate this change. This worker skipped a very important step. He did not verify with a with a test instrument that the equipment was de-energized ultimately costing the worker his life. He skipped step 7.
Gloves and arc flash gear if skip steps
Remember! Electrical equipment is can NOT be considered deenergized until an electrically safe condition has been established. In other words all 8 steps must be completed. If we skip a step such as not verifying the absence of voltage with a test instrument or not installing a lock and tag the equipment is not in an electrically safe condition and consequently it can't be worked on as such. Now we have to take additional precautions such as wearing PPE.