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A bolted fault consists of a low impedance short circuit between two separate phases or between phase and ground. Because of the low impedance path, the short circuit current present is very high compared to an Arc-fault in a similar system - a typical rule of thumb is that the bolted fault current a system is capable of sustaining is roughly twice that of an Arc-fault in a similar system .
Traditionally, electrical equipment was designed to withstand this very high bolted-fault current. However, a Bolted Fault rarely results in the devastating explosion associated with an Arc-fault and as such, electrical equipment that has only been type tested for resistant to a Bolted Fault may not maintain their integrity under and Arc Fault condition.
The majority of Low Voltage (480/440/415V) systems are not designed for resistance to arc-fault and will fail under such conditions. See video of LV MCC under arc-fault condition.
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