Electrical Safety Flashcards
What is voltage?
Voltage is the potential difference between a conductor and the ground.
It is the electrical pressure, or power.
Volts.
What is current? Context, electricity.
Current is the quantity or volume of electricity.
amps.
Name the regulations, standards, and codes governing the installation and design of electrical conductors and electrical powered equipment.
Provincial electrical codes and regulations are usually based on the Canadian Electrical code, and CSA 22.1, 22.2, and 22.3.
In BC this is the Electrical Safety Act, and Electrical Safety Regulation
Additionally, OHS regulations usually cover some electrical safety. There is often overlap between the legislation.
BC OHSR Part 19. Electrical Safety
The BC OHSR references the Electrical Safety Regulation.
What regulations govern work practices on and near energized equipment?
1, Provincial electrical code and regulations
(usually based on the Canadian Electrical Code, CAS 22.1, CAS 22.2, CAS 22.3)
In BC this is the Electrical Safety Act, and Electrical Safety Regulation
2, Provincial OHS regulations associated with electrical safety
In BC, this is the BC OHSR Part 19.
There is often overlap between electrical safety and OHS safety regulations.
What is GFCI? Context, electrical safety.
A Ground Fault Circuit Interrupter is a device that monitors the current in the hot and neutral wires of a cord. If there is 5 mA or more leakage, then the GFCI will cur the power.
A GFCI is not the same as a circuit breaker or fuse in an electrical panel. These trip when the current through the wire is too high, typically 10-30 A. At 10 A, the current is high enough to cause electrocution.
What is electrical resistance?
Electrical resistance is the amount that a material reduces the flow of electricity.
Ohms.
What is ohms law?
V = I x R (Voltage = current x resistance)
Variation
I = P ÷ E
V, voltage I, current (intensity) R, resistance P, power (watts) E, voltage (electromotive force, older notation than V)
What is low voltage?
BC OHSR, part 19 = 31-750 is low voltage.
What is high voltage?
BC OHSR, part 19 = 750+ volts is high voltage.
What is AC/DC?
AC = alternating current DC = direct current
Frequency of AC is measured in Hertz (Hz), cycles per second. Always 60Hz in Canadian homes.
Discuss electrical shock injuries.
Injuries caused by the bodies own electrical system being overloaded.
- Muscle damage from severe contraction
- Damage to non-muscle tissue from excess muscle contraction
- Cardiac arrhythm or arrest
Discuss electrical burns.
Electrical resistance converts electricity into heat. Burns can occur at entry site, exit site, or anywhere between.
An arc may be created resulting in arc or flash burns to the skin or eyes.
What are indirect electrical injuries?
Injuries incurred by electrical shocks other than shock and burn injuries.
For example, a fall or bring thrown from the electrical source.
What is the CSA?
The Canadian Standards Association
How can a professional design safe work practices for work on or near electrical systems?
1, If possible, de-energize the system before work
2, If possible, reduce the energy in the system
3, Only permit qualified workers to work on the system
4, Work with appropriately qualified workers to develop safe work practices
How can an OHS professional ensure that work on or near electrical energized equipment meets due diligence?
1, Know the regulations for the jurisdiction, including what is accepted as a qualified worker for the jurisdiction.
2, Confirm the qualifications of all workers.
3, Ensure that at least 1 qualified person assists in the writing of safe work procedures.
4, Limit risk by limiting the numbers of qualified and non-qualified workers permitted in the work area.
What is the cause of most accidental high voltage deaths & injuries?
Accidental contact with high voltage powerlines.
Investigations typically find:
- Work was usually near the power line and not on the power line
- Lines carried 25kv or less (standard commercial lines) and not 60-500kv lines (main, high power lines)
- Workers were aware of risk but didn’t implement appropriate controls
- Workers assumed that the power lines were insulated or protected in some way
- Additional workers were injured attempting rescue
What is the touch potential?
Touch potential is the potential difference in volts between a power source and the ground.
If a circuit contact is made between the two, then the electricity will travel along the circuit.
Example, power lines where a person touches the line and the pole supporting the line, completing the circuit to the ground.
What is step potential?
Touch potential is the potential difference in volts between two points on the ground.
When electricity is travelling to the ground (down power lines), the ground around the source becomes electrified. Further away from the source, the voltage gradually decreases. If a person stands with one foot on ground with 5kv, and another foot on ground with 4kv, then 1000v will travel through the worker to move from the high to low voltage areas.
What are limits of approach?
Prescriptive legislation that is generally found in all OHS legislation. It dictates the minimum distance workers or equipment may be to an electrically energized source. (with exceptions)
Example, BC OHSR Part 19, section 19.24.1
750V to 75kV = 3 meters
75kV to 250 kV = 4.5 metres
250kV to 550kV = 6 meters
What should a worker do if operating equipment that comes into contact with powerlines?
1, Remain in vehicle
2, Attempt to move vehicle to break contact
3, Warn other workers to maintain limits of approach to vehicle
4, If vehicle cannot be separated from powerlines, then remain in vehicle until help can be organized
5, If the worker must leave the vehicle (fire), then jump with feet together being careful not to stumble. Goal is to avoid touching ground and vehicle at the same time.
6, Keep feet together and carefully hop until out of limit of approach
Discuss accidents from low voltage electricity
Injuries and deaths from low voltage equipment are high. Possibly due to:
- uneducated people think that low voltage means low danger
- uneducated people may work on low voltage equipment at home, and so think that it is safe
- workers may have seen qualified persons working with energized low voltage equipment and think that they know all the hazards
- Standards and regulations for design and installation of electrical equipment in Canada are high. As such, many people do not hear about low-voltage accidents
- Many workers think that low voltage equipment has protective design features to keep them safe.
What should be done if work must occur within the limits of approach?
There is highly prescriptive legislation that follows the hierarchy of controls when work must be conducted within the limits of approach.
This includes de-energization when possible, and paperwork when it is not. WorkSafeBC must be notified, hazards must be clearly marked and a watcher is necessary.
What three steps can be taken to ensure that portable electric-powered tools do not become an electrocution hazard?
Only permit approved electrical tools and extension cords to be used.
Ensure that appropriate grounding is in place for all electrical tools and extension cords.
Use a ground fault interrupter, especially in wet locations.
