SJP-1 Arc Flash Hazards
CSA Z462: The New Canadian Electrical Standard is intended to help Canadian employers assess electrical hazards and design safer workplaces around electrical power system and machinery in accordance with the Canadian Electrical Code and other Canadian requirements.
What it Covers: the standard addresses the electrical safety requirements to safeguard workers during activities such as the installation, operation, maintenance and demolition of electric conductors and equipment, and raceways.
Training: Only employees with sufficient expertise, training and understanding of the existence, nature, causes and methods to prevent electrical hazards will be involved in any work where this may occur. This training would also include the selection and proper use of PPE. As part of regular electrical safety training, arc flash hazard topics will be included.
Understanding Arc Flash Quantities: Workers are expected to read signs/labels, drawings and tables to understand the degree of hazard they may be exposed to. Some of these pertain to the rating of the required PPE or protection boundaries. It is important that workers understand the following quantities and their units. An understanding of the physical significance of these quantities is helpful.
• Flash Protection Boundary
• Working Distance
• Incident Energy
• Hazard/risk category
• ATPV of PPE
Arc Flash Hazard Assessment: Arc Flash hazard assessment should be carried out by skilled and experienced professionals.
In the event it is necessary to work on energized equipment the following guidelines will apply:
a) face shields are not mandatory when working on control panel, PLC cabinet or control circuits where the voltage is 120v or less as the arc flash hazard is minimal in those areas. However, shock hazard still exist so appropriate gloves, eye protection and insulated tools are still required.
b) 50v to 600v (hazard/risk category 2 protection required)
Appropriately rated electrical protective will be worn:
Fire retardant coveralls with a minimum arc rating of 8 cal/cm2
Arc rated jacket, parka, or rainwear (when required)
Voltage rated rubber gloves with leather protectors
Hard hats, eye protection, hearing protection and CSA approved footwear
All live work will be restricted to testing only, with appropriately rated equipment
No one is allowed within a boundary of 4 feet without wearing the appropriate electrical protective equipment.
If there is a special circumstance where live electrical work is required, a specific safe job procedure for that work must be developed and implemented before starting any work.
Greater than 600 volts ( hazard/risk category 4 protection required)
Appropriately rated electrical protective equipment will be worn:
• Fire retardant clothing with a minimum arc rating of 40 cal/cm2
• Arc rated flash suit hood
• Arc rated jacket, parka, or rainwear (when required)
• Voltage rated rubber gloves with leather protectors
• Hard hats with fire rated liner, eye protection hearing protection and proper CSA approved footwear
Live work shall only be performed by personnel that are certified and authorized to work at the rated voltage level.
All live work will be restricted to testing only, with appropriately rated equipment.
Two people will be required; both wearing appropriately rated electrical protective equipment. * Standby person does not need to be an electrician however they need to be trained to know what to do should a problem arise.
No one allowed within a boundary of 10 feet with out wearing the appropriate electrical protective equipment.
Working on live Equipment
a) It is ALWAYS preferable to work on de-energized equipment, regardless of the hazard risk category. When work on live equipment is unavoidable, formal hazard assessments and safe job procedures will be developed and implemented.
b) Use insulated tools. Dropping of tools can cause momentary faults, sparks and arcs. Insulated tools can help reduce this type of accident.
c) Torque control: When using spanners, wrenches or screwdrivers to fasten or loosen a connection use appropriate torque. When excessive force is required, it is not uncommon to lose control. Slipping of screws or nuts and bolts may cause accidental touching. Corroded or heated fasteners can be difficult to loosen. Work off line if loosening is difficult.
d) Do not use paint, cleaning chemicals, spray. Etc. on live exposed metal parts. The fumes or spray may be conductive, and it may reduce the insulating property of air and allow an arc to strike through. Spraying directly on live conductors can also provide a conducting path that will result in electric shock.
*This information does not take precedence over current OH&S legislation with which all employees should be familiar
Exposure to Arc Flash Hazard can be limited in three ways:
a) Avoiding arc flash accidents
b)Reducing the level of arc energy released
c) The proper use of personal protective equipment (PPE)
Arc flash accidents can be reduced by following procedures correctly, use of proper tools, good preventative maintenance, planning and coordination of work, as well as skill development and practical experience. Also important is the mental and physical conditions of the workers, such that the dropping of tools, accidental touching, etc. are avoided. Taking care of the causes of arc flash is the principal strategy for avoiding exposure.
Accidents may occur despite precautions taken to avoid them. In such cases, it is always better if the incident energy is low, and the worker is prepared for the worst by using appropriate PPE.
Avoiding Arc Flash Accidents
Understanding its causes and taking steps to minimize them can avoid arc Flash.
The mitigation measures are described in the following sections:
a) Dust, impurities, and corrosion at surfaces producing heat, loosening contacts and
b) creating sparks
c) Sparks produced during racking of breakers, replacement of fuses, breaker/fuse
d) closing into faulted lines
e) Failure of insulating materials
f) Snapping of leads at connections due to force- human, rodents or birds
g) Accidental touching and dropping of tools, nuts/bolts, or metal parts
Preventative Maintenance
Preventative maintenance practices exist in most companies that require high reliability of supply or process continuity. Preventative maintenance also provides for a safer workplace.
a) Rodents and birds entering panels and switchgear are not uncommon. These can lead to short-circuits and eventually arc-flash. This risk can be prevented by closing all open areas of equipment with wire net or sealant so that rodents and birds cannot enter.
b) Use corrosion resistant terminals. Corrosion can lead to snapping of small wires, which in turn may create sparks and fumes when the tip of the wire hits the metal enclosure or another phase conductor. Check for corroded terminals and parts regularly if the electrical equipment is at a chemical plant or near a marine atmosphere. Electrical contact grease is typically used in joints and terminations. This will reduce corrosion.
c) Check for loose connections and overheated terminals. Impurities at the terminal connectors or dust can create additional contact resistance, heating the terminals. Heating of cable insulation can damage the insulation-another cause of flashover. Infra-red thermography can provide valuable data on poor connections and overheated electrical conductors or terminations.