The best time to discuss safety about electrical systems is all the time. New NFPA-70 NEC Article 110.16(B) states the following:
In other than dwelling units, in addition to the requirements in 110.16(A), a permanent label shall be field or factory applied to service equipment rated 1200 amps or more. The label shall meet the requirements of 110.21(B) and contain the following information:

• Nominal system voltage
• Available fault current at the service overcurrent protective devices
• The clearing time of service overcurrent protective devices based on the available fault current at the service equipment
• The date the label was applied

This is intended to provide the personnel maintaining the equipment to know what the hazard is behind the covers of the switchgear, panelboards, loadcenters, meters, etc. When opening gear to perform regular maintenance, it is critical to have a plan. Know what the risks are and what to do in the event of an incident.
Electrical shocks are part of OSHA’s fatal four. This includes Falls, Struck By, Electrocution, caught between/in. Often an electrocution can occur in conjunction with a fall or caught between/in. This is why knowing the surroundings, the risk and the emergency response should be paramount for every mechanic who is planning to work on or around live electrical equipment.
NFPA-70E has details and charts on determining proper PPE. Typically this will include an arc flash rated outfit, safety glasses or goggles, gloves, and hearing protection. All personnel working within the arc flash boundary must be protected at all times.
There are many situations when working in or around live electrical equipment and it is everyone’s responsibility to follow safe working practices.