On July 9, 2020, a mine superintendent was electrocuted while attempting to reverse the polarity of a 4,160 VAC circuit by switching the leads inside an energized 4,160 VAC enclosure that contained a vacuum circuit breaker and disconnect.

• Follow these steps before performing electrical work inside a high voltage enclosure:
  1. Locate the high voltage visual disconnect away from the enclosure that supplies incoming electrical power to the enclosure.
  2. Open the visual disconnect to provide visual evidence that the incoming power cable(s) or conductors have been de-energized.
  3. Lock-out and tag-out the visual disconnect yourself. Never rely on others to do this for you.
  4. Ground the de-energized conductors.
• Verify circuits are de-energized using properly rated electrical meters and non-contact voltage testers.
• Ensure properly qualified miners perform all work on high voltage equipment.
• Wear properly rated and well maintained personal protective equipment, including arc flash protection such as a hood, gloves, shirt and pants.
• Train miners on safe work practices for high voltage electrical equipment and circuits.

source: www.MSHA.gov