Electrical Safety Flashcards
What is an arc flash protection boundary (FPB)?
It is the distance at which a worker is exposed to the specific level incident energy.
What is an arc flash?
It is an electrical current that passes through air between ungrounded conductors or between ungrounded and grounded conductors that produces high temperatures.
What are ark flash hazards?
They are dangerous conditions associated with the possibility of release of energy caused by an electrical arc.
*arc flash hazards are in every electrical system.
What are arc faults?
They are high power discharges of electrical energy that change into heat.
What happens during an arc flash event?
And arcing fault releases a huge amount of energy. Steel and copper can change from solid to vapor, creating an explosive pressure wave. The amount of energy released depends on the voltage, available fault current and clearing time of overcurrent protection devices.
What would happen to a person if they were exposed to an arc flash event?
They would likely receive severe burns, shrapnel embedded from the blast, temporary blindness and temporary hearing loss.
What is the document most referenced for electrical safety?
The Canadian Standards Association (CSA) Z462: Workplace Electrical Safety.
Arc Flash Hazard Analysis determines what?
The risk of personal injury as a result of exposure to incident energy from electrical arc flash.
What is a flash protection boundary?
It is an approach limit at a distance from exposed to live parts within which a person could receive a second-degree burn if an electrical arc flash were to occur.
What equation is an arc flash protection boundary (FPB) measured by?
1.2 calories/cm²
What is incident energy exposure?
It is the amount of thermal incident energy to which of workers face and chest could be exposed at working distance during an electrical arc event.
What is an arching fault current?
And arcing fault current results from the short-circuit or electrical contact between two conductors at different potentials in which the impedance or resistance between the conductors is essentially zero.
What is arc duration?
It is the total time it takes system protective devices (breakers, fuses) to detect and interrupt fault current.
What is the definition of a qualified person?
A qualified person is one who has the skills and knowledge related to the construction and operation of the electrical equipment and installations and has receive sufficient training to recognize and avoid the hazards involved.
What are the three shock protection approach boundaries?
Limited approach boundary, restricted approach boundary and prohibited approach boundary.
How many hazard/risk category (HRC) levels are there? What are they numbered? In how many levels do you need to wear arc-rated PPE clothing?
5 levels numbered 0-4. Arc-rated PPE must be worn in levels 1 through 4.
What is one abnormal condition that can increase the risk of exposure to arc flash?
(Any 1) Hinged doors on energized equipment. Electrical equipment covers that are open. Over current conditions where the gap between conductors is compromised. Energized electrical equipment operating near flammable or conductive dusts.
Arc flash can be caused by a number of things, name four:
•Dust or conductive dust in electrical equipment •dropping tools inside of electrical equipment •accidental touching of electrical equipment •condensation in the electrical equipment •material failure •corrosion •faulty installation
What are the three factors that determine the severity of an arc flash injury?
- proximity of the worker to the hazard 2. temperature
3. time it takes the circuit to break
What are some negative effects from an arc flash?
- Burns from clothing burning onto skin
- fire
- flying objects such as molten metal
- blast pressure upwards of 9700 kg/m²
- A sound blast in which noise can reach 165 dB
- heat upwards of 20 000°C
What does PPE stand for?
Personal protective equipment
What must a label on energized equipment have?
- The nominal system voltage
- the arc flash boundary
- the date of the hazard analysis
*The calculation method and data to support the information for the label must also be documented on the label
A label on energized equipment must also have at least one of these:
- The available incident energy and the corresponding working distance
- The minimum arc rating of PPE
- The required level of PPE or
- The hazard/risk category for the equipment
What is the purpose of wearing PPE?
To protect the users body from physical injuries caused by heat, electricity, contact with chemicals and airborne particulates. Helps reduce the risk of serious injury.
PPE selection is based on one of two methods:
- The amount of incident energy exposure or
2. The hazard/risk category
In all cases, de-energizing the system prior to performing work is the preferred method of protecting workers
True or False
True
Basic compliance to CSA Z462 requirements is established with a five step process for safety and operability
True or False
True
What is the lockout?
The process of ensuring that machinery or equipment does not turn on or move during installation, repair or maintenance.
What are the six basic steps for locking out and re-energizing equipment when you need to work on it?
- Advise everyone
- Shut down the equipment
- Disconnect the equipment
- Install a lock and tag them
- Check the equipment to confirm it’s
isolated - Confirm it’s safe to re-energize
When is the lockout used?
When there are many persons of the same trade or different trades working on different parts of the same equipment to be repaired.
What is a safe distance to maintain when working on or operating machinery near overhead power lines?
7 m
Describe an electrical shock:
Electrical shock interferes with the normal electrical signals in the human body and can cause the heart rhythm to dangerously change or to stop
What is the average resistance of dry skin?
100,000 ohms to 600,000 ohms
What is the resistance of wet skin?
1000 ohms
Voltage is the killing factor in electrical shock
True or False
False, The current is the killing factor in the electrical shock, voltage determines how much current flows through given body of resistance
What are the five steps to take in the event of an electrical emergency?
- Remove the victim
- prevent further injury
- send for qualified help
- eliminate the danger and
- report the accident
Which code governs safety rules and standards to be observed at worksites?
The OHSA, the occupational health and safety code found at the Workers Health and Safety website
What amount of current causes ventricular fibrillation of the heart?
100 mA to 200 mA
An extension ladder should be placed with its base ____ of the length of the ladder from the wall it is leaning against.
1/4
What amount of current causes breathing to be difficult?
20 mA to 75 mA
What amount of current causes muscular control to be lost?
15 mA to 20 mA
Adjustable locking pliers can be adjusted to a closed jaw width and lock in the closed position
True or False
True
Lineman’s pliers are also referred to as:
Klines
Pump or locknut pliers are adjustable jaw pliers for use on ____ and ____. They can also be referred to as ____.
lock nuts and conduits. Channel locks.
List three types of screwdrivers:
The flat blade, the Phillips and the Robertson
Adjustable wrenches are also called ____ wrenches.
crescent
What are 4 types of wrenches:
- adjustable wrenches
- pipe wrenches
- box and open end wrenches
- set screw wrench
The pitch of a hacksaw blade refers to what?
Teeth per inch TPI
A good pitch of a hacksaw for cutting electrical metallic tubing is a ____ TPI blade; an ____ TPI blade would be better for rigid conduit
32, 18
The ____ of the blade refers to the amount that the teeth are turned to one side or the other from the center of the blade and determines the thickness of the cut.
set
