Arc Flash is light and heat produced as a result of Arc Fault, due to low impedance path, which causes electrical explosion or discharge.
Arc Flash is light and heat produced as a result of Arc Fault, due to low impedance path, which causes electrical explosion or discharge.
As per NFPA 70E, arc flash is a “dangerous condition associated with the release of energy caused by an electrical arc.” It is measured in terms of arc flash incident energy (AFIE), which is used to determine the level of personal protection equipment (PPE), and in terms of an arc flash protection boundary.
Arcing faults occur when electrical clearance is compromised.
Causes of Clearance reduction/Compromise can be:
Insulation Deterioration
Screwdriver/conductor/wrenc fall/drop
Inshort conducting path is temperory/accidental.
Bolted faults are caused due to mistakes done during installation or maintenance. In this case by mistake opposite phases or phase-to-ground are connected together (bolted). Switchgear upstream of the fault opens to protect the system, While doing so Arcing occurs inside the protection device as contacts inside Switchgear opens.
The amount of energy released during an arcing fault is a function of the available fault current (Fault Feeding Capacity of Trafo/DG) at the point in the system reduced by the dynamic impedance of the arc and the time the arc persists.
In Order to limit the avaibale fault current, current limiting breakers are better equped to limit Arc Flash Energy.
The Current Limiting Circuit Breakers limit the let-through current and Arc Flash incident energy.
Category A Breakers are Current Limiting.