T&D World Magazine

Arc Flash Protection Features Upgrades

The ABB Low Voltage Products division has released TVOC-2, a new generation of its Arc Guard System that has been protecting electrical equipment from dangerous electrical arc flashes for more than 35 years. TVOC-2 features numerous upgrades and new functions to provide superior arch flash protection, detecting faults in low- and medium-voltage switchgear and disconnecting the power provided to the arc within 30 to 50 milliseconds, preventing serious injury to personnel and damage to expensive equipment. Without the Arc Guard System an arc flash will typically trip a circuit breaker in approximately one second, enough time for the arc to destroy the switchgear and kill or seriously injure a person.

TVOC-2 is now UL listed, and when installed along with ABB’s Emax circuit breakers, carries a functional safety rating of SIL-2 as certified by TÜV Rheinland, an independent global provider of safety analysis. The SIL-2 certification confirms that the TVOC-2 has achieved the standard required to protect both humans and equipment.

The Arc Guard system can detect an arc flash in less than one millisecond, and depending on the disconnecting device, it will typically disconnect the power to the switchgear within 30 to 50 milliseconds. This will not prevent the accident, but it will significantly reduce the damage.

The Arc Guard System uses light as the main condition to instantaneously trip the incoming circuit-breaker, responding in milliseconds and overriding slower protection elements. The system acts in three phases:

  • Detection - on optical sensor senses when light (an arc flash) is inside the equipment
  • Recognition - the arc monitor determines the intensity of the light
  • Action - the TVOC-2 sends a signal to trip the breaker(s)

Short circuit protection alone is not enough to provide the necessary response time because power distribution systems often include a required selectivity designed to achieve desired plant efficiencies and ensure power availability. This selectivity delays the breakers tripping in the necessary time. The Arc Guard System, along with properly specified circuit breakers, overrides the protection delays within the necessary timeframes to minimize injuries and equipment damage.


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