One method of mitigating arc flash hazards associated with medium-voltage switchgear is the installation of active high-speed switch (HSS) systems. These systems are designed to detect and quench a burning internal arc in less than one-third of one electrical cycle. The internal arc is extinguished by the HSS's action of redirecting the fault current path from arcing through open air back to the intended current path of the switchgear bus. The new low-impedance current path provided by the HSS operation collapses the voltage at the point of the fault to near zero so that the arc is no longer sustainable. The system's high speed of operation compared to arc quenching via circuit breaker tripping translates directly to lower arc flash incident energy and minimal equipment damage. Another benefit of such active high speed systems could include switchgear compliance to the IEEE C37.20.7 guide for testing arc-resistant metal-enclosed switchgear without any arc by-product venting requirements. This paper explores application considerations of HSS systems relative to other available means of controlling and reducing the hazards of internal arcing faults in medium-voltage switchgear. Index Terms-Arc flash incident energy (AFIE), arc resistant, arcing fault, bolted fault, high-speed switch (HSS), X/R ratio.

One method of mitigating arc flash hazards associated with medium voltage switchgear is the installation of active, high speed switch (HSS) systems. These systems are designed to detect and quench a burning internal arc in less than one third of one electrical cycle. The internal arc is extinguished by the high speed switch's action of re-directing the fault current path from arcing through open air back to the intended current path of the switchgear bus. The new lowimpedance current path provided by the high speed switch operation collapses the voltage at the point of the fault to near zero so that the arc is no longer sustainable.