Electricity is a part of our everyday lives and it can be dangerous is the fact we all know. But the hazards associated with electricity are taken so lightly. Most of us believe that we are in a safe environment because no such hazard had taken place before, is it logical enough to think that way even when you are working in a field, where logic and practicality matter more.
Only a second lapse in judgment or one small factor that is out of our control can be the difference between life and death. Arc Flash hazard is this kind of matter.
When any short circuit happens between two live conductors in an electrical network either by direct contact or indirect contact, it will lead to a fault in the electric network. This fault will generate an electric arc which in turn leads to a flash which is generally known as electric arc flash.
The temperature of an arc flash can reach 35,000 degrees Fahrenheit – which is up to four times hotter than the sun. This means to maintain a safe workplace it is important to analyze the system properly. Statistics indicate that based on hospitalization records, Arc flash accidents that involve a fatality or serious injury to an employee occur frequently in India. Those incidents most often occur when personnel is required to work on electrical equipment while it is in an electrically energized condition.
Source – The Hindu
It is normal human behavior to look for a solution when the problem has occurred already. Only a few think of the solution which will prevent the system/people to get affected by the problem.
precautionary measures can be taken following mentioned way
1. Label Equipment
The standard labeling procedure is to conduct a survey of the premises and compile details of the electrical system. The system is analyzed at each of the panel boards, motor control centers, switchboards, transformers, and, medium-voltage equipment on the premises.
From the compiled calculated values the labels are prepared, and then applied to the equipment.
2. Train Personnel On Proper Safety Practices
Unsafe human procedures especially mishandling or unintended contact with energized equipment and tools. Therefore, educating employees facing a high risk of an electrical accident on recognizing the dangers is of prime importance when it comes to preserving people’s physical integrity.
3. Reduce Available Fault Current
3.1 Circuit Breakers & Fuse –
Circuit breakers and fuses determine how fast a circuit is cleared.
Incident energy is proportional to arcing time, Hence the use of faster-acting devices is key. Proper selection of overcurrent protective devices, in particular, selecting devices that will quickly clear arcing faults from the power system is a powerful mitigation strategy.
3.2 Protective Device Coordination Study
Protective device coordination study optimizes the protective device setting for reliability and arc flash protection. This coordination study will determine if minor adjustments in circuit breaker settings can lower incident energy levels or the circuit need to be replaced.
Settings must be chosen to properly protect equipment while still allowing for normal load currents and routine temporary overcurrents (e.g., motor starting current) to flow without causing a trip.
3.3 Specialized Relaying, Such as Optical Technology
A relatively new way to address this issue is to use relays that detect the presence of arcing faults by looking for the flash of light associated with the arcing fault in addition to the characteristic current flow
3.4 Virtual Main Arc Flash Mitigation System
This mitigation solution can take one of two forms:
A maintenance selector switch, which temporarily lowers the instantaneous short circuit current setting. The maintenance setting lowers the available arc flash incident energy and temporarily abandons selective coordination.
Zone-selective interlocking with downstream branch circuit breakers in the switchgear eliminates the need for the maintenance selector switch. Arc flash energies can be permanently reduced with zone-selective interlocking.
4. Redirect Blast Energy
Redirecting energy produced by an arc flash away from personnel can be an important safety strategy. AR(Arc Resistant) switchgear can accomplish this. Manufacturers design this specialized equipment to contain and exhaust arc blasts.
5. Faster Clearing Time
Clearing time is the amount of time it takes a circuit protection device to clear a fault. the flash will continue to expand until the upstream overcurrent protective device, such as a circuit breaker or fuse opens the circuit shutting off the supply of energy. If a fuse that blows quickly or has what’s called a short clearing time is installed in the circuit, the subsequent arc flash will be small because it doesn’t have time to grow. If the circuit relies on a fuse that has a long clearing time the flash could expand to a dangerous level.
As the accidents associated with electricity have been increasing from last decade in India. It is now advisable to take precautionary measures beforehand to avoid any serious injury or fatality. To deal with such incidents Arc flash study and protective device coordination study is required to ensure workplace safety and increase system reliability.