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September 05, 2021
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 their original volume when vaporized. The arc flash/blast produces fire, intense light, pressure waves and flying shrapnel. 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 electrical safety training. There are a variety of reasons why an arc flash can occur, but most of them are human error and preventable. Many arc flashes occur when maintenance workers are manipulating live equipment for testing or repair and accidentally cause a fault or short circuit. Improper tools, improper electrical equipment, corrosion of equipment, improper work techniques and lack of electrical safety training are just some of the events that can lead to a devastating arc flash or arc blast.
Causes of arc flash incidents
One of the primary reasons for electrical injuries is electric arcing, commonly referred to as arc flash. Arc flash incidents are often related to human error when work is being performed on or around energized electrical equipment. Even when the work involves control equipment and the handling of small, low-voltage electrical components, the risk of arc flash still exists. An arc flash may cause severe burns, hearing loss, eye injuries, lung damage, and blast injuries. Arc flashes are rare but when they do happen, the impact on personnel and the business can be significant. Maintaining a heightened sense of awareness can help to protect equipment and save lives.
“an arc flash may cause severe burns, hearing loss, eye injuries, lung damage, and blast injuries”
Accidental contact
Working around exposed, live parts presents a hazard, and the fact is –accidents do happen. When it comes to accidents around electrical equipment, a mere drop of a tool or physical contact with the live part can set off an arc flash and instantly generate an energy explosion releasing temperatures in excess of 35,000˚F.
Testing and troubleshooting live equipment
The importance of uptime for critical processes often results in the need to perform troubleshooting on live equipment. If a test probe accidentally establishes a phase-to-phase or phase-to-ground connection during a routine check, it could result in personal injury and downtime. Ensuring the right tools are used for the job will help to reduce the risk and probability of an arc flash occurring.
Installing and operating live equipment
Adding or removing circuit breakers, contactors or components in energized control circuits or motor control centre (MCC) buckets, or installing or removing MCC buckets from a live bus, can all incite an arc flash. Routine operation of breakers and disconnect switches, especially racking breakers in or out of both low and medium-voltage switchgear, all present a risk of arc flash in equipment that has not been properly installed, tested and maintained.
The poor condition of the equipment
Damaged insulation, or loose or incorrectly wired control connections, can all lead to failures and ultimately arc flash incidents. Insulation breakdown can cause arcing or heat, potentially triggering an arc flash. It is important to verify the integrity of cable installation prior to working on any electrical equipment. Missing or damaged insulation, barriers and guards may increase worker exposure to hazardous locations and components. Damaged equipment enclosures, operating mechanisms, and cable/bus supports are important factors in assessing the likelihood of exposure to hazards and the probability of an accident occurring.
Improperly maintained equipment and tools
The primary purpose of a circuit protective device is to interrupt current flow after a downstream short circuit or fault is detected. If the protective device has not been properly maintained and it fails to interrupt the fault, the result could be an explosive arc flash and the ensuing damage to equipment and personnel. Regular testing and preventative maintenance can help ensure the equipment will operate within the manufacturer’s limitations. Poor environmental conditions, such as moisture, or a build-up of conductive dust or contaminants, can result in corrosion or compromised insulation systems. Damaged or improperly rated tools and test equipment, including worn insulating material for screwdrivers and wrenches, can lead to accidental arcing from conductors to the ground.
Arc flash risk assessment
An arc flash risk assessment is required to determine the risk level of all areas in which employees perform work. This is essential to ensuring worker safety and helps save lives and money by minimizing the risk of injuries and lost time due to accidents.
In general, arc flash risk assessment includes the following:
Data Collection – Collect necessary data about the facility’s power distribution system, including details of all three-phase electrical components, nameplate specifications, and lengths and cross-section of all cables.
Engineering Analysis of the Data – Perform a short circuit analysis followed by a coordination study and determine the minimum PPE requirement.
Protective Device Coordination – Coordinate PPE to ensure selection and arrangement are sufficient for mitigating arc flash hazards.
Arc Flash Calculations – Determine incident energy levels and flash protection boundaries, and complete calculations of all relevant equipment busses.
Arc Flash Study and Analysis Report – Once the calculations are done, deduce the results of the report carefully.
Label Installation – Create and install warning labels pinpointing incident energy and working distance, arc flash boundary, and nominal system voltage. Include limited and restricted approach boundaries, date, upstream protective device, and recommended personal protection equipment (PPE) as well.
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 their original volume when vaporized. The arc flash/blast produces fire, intense light, pressure waves and flying shrapnel. 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 electrical safety training. There are a variety of reasons why an arc flash can occur, but most of them are human error and preventable. Many arc flashes occur when maintenance workers are manipulating live equipment for testing or repair and accidentally cause a fault or short circuit. Improper tools, improper electrical equipment, corrosion of equipment, improper work techniques and lack of electrical safety training are just some of the events that can lead to a devastating arc flash or arc blast.
Causes of arc flash incidents
One of the primary reasons for electrical injuries is electric arcing, commonly referred to as arc flash. Arc flash incidents are often related to human error when work is being performed on or around energized electrical equipment. Even when the work involves control equipment and the handling of small, low-voltage electrical components, the risk of arc flash still exists. An arc flash may cause severe burns, hearing loss, eye injuries, lung damage, and blast injuries. Arc flashes are rare but when they do happen, the impact on personnel and the business can be significant. Maintaining a heightened sense of awareness can help to protect equipment and save lives.
“an arc flash may cause severe burns, hearing loss, eye injuries, lung damage, and blast injuries”
Accidental contact
Working around exposed, live parts presents a hazard, and the fact is –accidents do happen. When it comes to accidents around electrical equipment, a mere drop of a tool or physical contact with the live part can set off an arc flash and instantly generate an energy explosion releasing temperatures in excess of 35,000˚F.
Testing and troubleshooting live equipment
The importance of uptime for critical processes often results in the need to perform troubleshooting on live equipment. If a test probe accidentally establishes a phase-to-phase or phase-to-ground connection during a routine check, it could result in personal injury and downtime. Ensuring the right tools are used for the job will help to reduce the risk and probability of an arc flash occurring.
Installing and operating live equipment
Adding or removing circuit breakers, contactors or components in energized control circuits or motor control centre (MCC) buckets, or installing or removing MCC buckets from a live bus, can all incite an arc flash. Routine operation of breakers and disconnect switches, especially racking breakers in or out of both low and medium-voltage switchgear, all present a risk of arc flash in equipment that has not been properly installed, tested and maintained.
The poor condition of the equipment
Damaged insulation, or loose or incorrectly wired control connections, can all lead to failures and ultimately arc flash incidents. Insulation breakdown can cause arcing or heat, potentially triggering an arc flash. It is important to verify the integrity of cable installation prior to working on any electrical equipment. Missing or damaged insulation, barriers and guards may increase worker exposure to hazardous locations and components. Damaged equipment enclosures, operating mechanisms, and cable/bus supports are important factors in assessing the likelihood of exposure to hazards and the probability of an accident occurring.
Improperly maintained equipment and tools
The primary purpose of a circuit protective device is to interrupt current flow after a downstream short circuit or fault is detected. If the protective device has not been properly maintained and it fails to interrupt the fault, the result could be an explosive arc flash and the ensuing damage to equipment and personnel. Regular testing and preventative maintenance can help ensure the equipment will operate within the manufacturer’s limitations. Poor environmental conditions, such as moisture, or a build-up of conductive dust or contaminants, can result in corrosion or compromised insulation systems. Damaged or improperly rated tools and test equipment, including worn insulating material for screwdrivers and wrenches, can lead to accidental arcing from conductors to the ground.
Arc flash risk assessment
An arc flash risk assessment is required to determine the risk level of all areas in which employees perform work. This is essential to ensuring worker safety and helps save lives and money by minimizing the risk of injuries and lost time due to accidents.
In general, arc flash risk assessment includes the following:
Data Collection – Collect necessary data about the facility’s power distribution system, including details of all three-phase electrical components, nameplate specifications, and lengths and cross-section of all cables.
Engineering Analysis of the Data – Perform a short circuit analysis followed by a coordination study and determine the minimum PPE requirement.
Protective Device Coordination – Coordinate PPE to ensure selection and arrangement are sufficient for mitigating arc flash hazards.
Arc Flash Calculations – Determine incident energy levels and flash protection boundaries, and complete calculations of all relevant equipment busses.
Arc Flash Study and Analysis Report – Once the calculations are done, deduce the results of the report carefully.
Label Installation – Create and install warning labels pinpointing incident energy and working distance, arc flash boundary, and nominal system voltage. Include limited and restricted approach boundaries, date, upstream protective device, and recommended personal protection equipment (PPE) as well.
SOURCE:
https://www.hsmemagazine.com/article/gone-in-a-flash/
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