Electrical Safety

26102 Electrical Safety Part 3

Arc Flash

Arc Flash boundaries prevent people that are not properly trained from entering an area of Arc Flash Danger. Unqualified people may enter the LIMITED APPROACH BOUNDARY. People qualified and wearing PPE can be inside the restricted approach boundary.

Multiple Choice

Never work on an electrical circuit until you have turned off the circuit breaker.  

• True
• False

Arc Flash

What Is An Arc Flash? An Arc Flash is an electrical explosion due to a fault condition or short circuit when either a phase to ground or phase to phase conductor is connected and current flows through the air. Arc flashes cause electrical equipment to explode, resulting in injury or death to workers and destruction of electrical equipment.

Temperatures may exceed 35,000° F (the surface of the sun is 9000° F). These high temperatures cause rapid heating of surrounding air and extreme pressures, resulting in an arc blast. The arc flash/blast will likely vaporize all solid copper conductors which will expand up to 67,000 times its original volume when it is vaporized. The arc flash/blast produces fire, intense light, pressure waves, and produces flying shrapnel.

Arc Flash

When an arc flash happens, it does so without warning and is lightning quick. The result of this violent event is usually destruction of the equipment involved, fire, and severe injury or death to any nearby people. Proper safety and protection measures must be taken to limit the damage from an arc flash which include conducting an arc flash study, short circuit study, and NFPA 70E electrical safety training.

The severity of a Shock

An outside current of as little as 75mA is enough to put the heart into fibrillation. Watch the video on the next slide and answer the questions that follow.

Burns

• The Most common injury associated with an electrical shock is a burn.

• There are 3 types of burns associated with Electrical Shock

Electrical Burns

Tissue damage as a result of current flowing through the tissue or bones. Most of the burning is internal and therefore is one of the most dangerous types of burns.

Arc Burns

This type of burn occurs when you get hit with the arc of an electrical arcing incident. Metal as hot as 35,000° can hit you as the incident occurs. This is why we have limited and restricted approach boundaries.

Thermal contact burn

This type of burn occurs when you are hit with the pressure wave and the copper expanding. Copper can expand at a factor in excess of 67,000 times vaporizing it . When the air gets superheated in these situations the air expands and is forced out at the weakest point. This is why doors and fronts of equipment blow off.

Multiple Choice

What is the most severe type of burn

• Thermal contact

• Arc

• Electrical Burn

Multiple Choice

Which factor determines the outcome of an electrical shock?

• The amount of current

• Which phase is involved

• The raceway system

• The size of the electrical equipment being used

Analyzing human performance helps pinpoint error points. Workers operate in one or more human-based performance modes: Rule-Based, Skill-Based, and Knowledge-based.

Rule-based Mode

• There is a procedure or set of rules applied when a task is being done.

• Common errors in this way of working are people that deviate or modify from established procedures.

• This is the most desirable mode for a worker to work in because if they follow the procedure then the outcome is likely known.

Knowledge-Based Mode

• This is the mode workers rely on when there is no procedure to follow

• Workers rely on past knowledge and past experiences to make informed decisions

• Most errors occur in this mode when workers focus on one problem and not the big picture or when they rely on faulty past information.

Multiple Choice

A live-dead-live test is conducted in order to?

• disconnect switches and fuses
• verify the test instrument operation
• make sure the capacitors are discharged
• verify that a circuit is de-energized

Skills Based Mode

• Workers rely on skills when performing basic tasks like installing a receptacle or flipping on a breaker.

• Common errors are lack of perceived risk because they have done the task many times before with no problems.

Multiple Choice

This mode relies on procedures and is the most desirable mode to work in

• Rule-based

• Knowledge-based

• Skill-Based

• Answer Based

Multiple Choice

The normal beating of a heart can be upset by an electrical current as small as?

• 1mA
• 30mA
• 75mA
• 1,000mA

Open Ended

What are 3 things that could have prevented this problem or lessened the severity of the accident in the previous video?

Open Ended

What does the STAR acronym stand for and how is it used(pg32)?

Open Ended

What do you think it means when you hear the phrase" Electricians have a ladder last policy when working on a job site"?