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Monday, May 2, 2022

Question:

Hello CQD.

When disconnecting a temporary flexible power cable equipped with three-phase plug and receptacle, should you de-energize the power supply before disconnecting the connectors? As a tradesperson we were always taught to de-energize first in case there was a wiring problem or a ground problem that could make the casing of the connector live. Would you ever advise an employee to try and disconnect the same connection if someone was being electrocuted? Or should they de-energize the three-phase temp power cord at the power supply? I have found multiple fatalities over the last 20 years where employees have tried to disconnect three-phase connections while energized and receive fatal electrocution from hidden hazards. This could be prevented if the source was de-energized before breaking the connection. I look forward to hearing your response.

Bradley Peaman

A

Answer:

Greetings Bradley,

Always follow the requirements in NFPA 70E relative to energized work. Based on the information provided this is not justified energized work and an electrically safe working condition should be established to perform it. See NFPA 70E Sections 110.1 through 110.4. De-energizing (elimination of the hazards) before performing the work is always the first priority. There are federal requirements as well in OSHA 1910 Subpart S and 1926 Subpart K depending on if the work is general industry or construction. 

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CHARLIE TROUT: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Even though Charlie passed away in October of 2015, his work continues in spirit. NECA continues to maintain this question forum for its many subscribers in memory and recognition of all his significant contributions to making the NEC what it is today.

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