51. DetectionThe arc fault is reliably detected by means of two separate tripping criteria. The arc fault produces an overcurrent which is detected by means of measuring current transformers. The second detection criterion is the extremely intense light emitted from an arc fault. This light is detected with fiber optic sensors. Some of this intense light emission enters the core of the fiber optic loop radially. Then this signal can be evaluated at the receiver side of the sensor. Any incorrect releases due to flashes or welding arcs are prevented by evaluating both signals together.3. QuenchingThe arc quenching device ensures extremely fast mitigation times. A three-phase short-circuit is produced in less than 1 ms in order to remove energy from the arc fault. A pyrotechnically initiated actuator, as used in airbag systems, fires a copper bolt that penetrates an insulation plate to establish electrical contact.2. EvaluationThe analog sensor signals are converted to digital ones in so-called detection modules and then passed on to the central evaluation unit (master). For this an internal communication bus has been developed which has the principal task of transferring any triggering information at ultra-high speed. The detection modules are also fed with power via this line. Each module has an independent address over the interlink assigned to one busbar section, the so-called protection zone. For monitoring of two or more busbar sections, it is possible to build up complex arc protection systems via the “masterlink”.4. DisconnectionThe incoming circuit-breaker has the task of disconnecting the affected busbar section from the mains supply. This is initiated by the short-circuit release. Each incoming circuit-breaker on this busbar section is sent an additional disconnection command to the shunt release as a backup measure. Busbar sections that are not affected remain operational.Controlling Arc Faults Safely
