6 ABB ARC GUARD SYSTEM™ – TVOC-2Short-circuit faults in LV and MV switchgears are often accompanied by an electric arc. An arc fault can leads to considerable damage to equipment and injury to personnel unless it is detected very quickly. To avoid serious damage and give the person involved a good chance of surviving the accident without severe injury, the fault should be disconnected as fast as possible, typically in less than 50 ms.The Arc Guard System™ quickly detects an arc fault and trips the incoming circuit-breaker. Using light as the main trip criteria, it trips almost instantaneously. Thanks to this key functional advantage, it overrides all other protections and delays, which is crucial when reaction times need to be measured in milliseconds.How it worksThe system acts in three phases:—System description 1 Detection The TVOC-2 detects the light from an arc flash 2 Recognition The system determines the intensity of light 3 ActionThe system sends signal to trip breaker(s)The diagram below shows how the exponential increase in energy over time affects different switchgear materials.Total clearing time = ABB Arc Guard System™ + breakerTot a l clearing time030-501001502007008009001 sec...0.2 sec Steel fire0.15 sec Copper fire0.1 sec Cable fireEnergy k A²s
