Electrical Safety

Obj 1 - safe work practice to protect from arc flash

• Arc flash is responsible for approx 50% of electrical deaths in workplace.

• Arch flash is possible in every electrical system

• Arch Flash hazard analysis - done to determine risk of personal injury

• Arc Flash Protection Boundary: distance for specific level incident energy. Used to determine PPE needed.

• Flash protection Boundary: distance from exposed live parts within which a person can receive a second degree burn if arc flash occurs

• Working distance: distance between person standing in front vs front of live equipment.

• Incident Energy exposure: amount of thermal energy during the arc. J/cm2 or cal/cm2.

• PPE: barrier between wearer and work environment. Last line of defense.

• 3 approach boundaries:

  • Limited Approach:

    • only qualified persons, if unqualified - must be escorted.

  • Restricted Approach:

    • only qualified persons, requires use of shock protection techniques.

    • Documented work plan needed and PPE.

  • Prohibited Approach:

    • only qualified persons, requires use of shock protection techniques.

    • Specially written, approved, work plan needed and PPE.

• When incident energy exceeds 40 cal/cm2, greater emphasis must be placed on de-energizing equipment.

• 5 levels of hazard/risk categories:

  • 0 = N/A arc rating, clothing must be non synthetic and non flammable

  • 1 = 4 cal/cm2, FR clothing needed in 1 layer

  • 2 = 8 cal/cm2, FR clothing needed.

  • 3 = 25 cal/cm2, FR clothing and ARC Flash suit needed (2 or 3 layers)

  • 4 = 40 cal/cm2, FR clothing and ARC Flash suit needed (3 or more layers)

• 3 factors determine arc flash severity:

  • Proximity

  • Temperature

  • Time it takes for circuit to break

• According to CSA Z462, employers must develop and implement an Electrical Safety Program. this is a 5 step process:

  • Step 1 - employer develops program procedures - living document

  • Step 2 - electrical system engineering study by professionals - live equipment to be marked by a label containing:

    • available incident energy

    • min PPE arc rating

    • required PPE level

    • highest hazard/risk category

  • Step 3 - conduct regularly scheduled safety training and audits

  • Step 4 - ensure adequate PPE supplies

  • Step 5 - maintenance of all electrical distribution system components

• Arc flash PPE minimizes burn injury and provides extra seconds of protection.

• Hazard/categories are rated from 0-4.

  • 0 = 4.5 oz/yd2

  • 1 = 4 cal/cm2

  • 2= 8 cal/cm2

  • 3= 25 cal/cm2

  • 4= 40 cal/cm2

  • Higher number is more dangerous

  • minimum arc blast is 4 cal/cm2 which is category 1 = FR apparel states cal/cm2 rating on it.

  • CSA Z462 outlines this PPE.

  • Realistically there are only 4 categories that specify ARC rated FR clothing.

• Arc flash protection boundary is distance at which a worker is exposed to 1.2 cal/cm2 incident energy. this is the distance at which PPE must be work to prevent 2nd degree burns from arc flash.

Obj 2 - Lockout procedures

• Do not put your lock through another person’s lock

• Each lock needs a tag including a warning to not operate, person’s name, signature, date lock was installed.

• Always confirm equipment isolated beofre starting work.

• No one can remove your lock for you.

  • locks cannot have a common key. your key must be the only one.

  • to facilitate multiple locks on a single switch or valve, “lockouts” are used (the common clasp where multiple people can place their lock)

• Do not open a breaker first before shutting down a motor (live load can create arc flash hazard).

• Always test start after locking out.

• OSHA 39 general safety regulations require that machinery is locked out and tagged.

• Potential electrical dangers are not always obvious!

• IF line voltage of a powerline is unknown, maintain a safe distance of 7 meters.

• Current levels and effect

  • 1mA = no sensation

  • 1-8mA = shock sensation not painful

  • 8-15mA = painful shock

  • 15-20mA = painful shock with muscular contraction

  • 20-75mA = painful shock with severe muscular contraction, hard to breathe

  • 100-200mA = painful shock, ventricular fibrillation of heart. Often fatal.

  • 200mA + = severe burns, stops heart, artificial respiration needed immediately.

  • Current is what kills, voltage determines how much current will flow based on your body’s resistance.

• Emergency Action

  1. Remove victim

  2. Prevent further injury

  3. send for qualified help

  4. eliminate danger

  5. report accident