12 ABB ARC GUARD SYSTEM™ – TVOC-2—ApplicationsBasic installation tipsArc monitor (TVOC-2)The Arc monitor can be mounted anywhere in the switchgear, e.g. in the breaker cubicle or in a separate control cabinet. Tripping is handled by a separate tripping circuit. The task of the Arc monitor is to close the circuit very quickly. You can connect up to 3 breakers in this way and, if required, trip different breakers depending on where the arc occurs. CSU (Current Sensing Unit)The CSU is an accessory used if you cannot prevent direct sunlight or other highly intensive light reaching the sensors frequently. CSUs can be mounted in series if more than two are needed. Connection of current transformers (for CSU)The CSU measures either 1, 2 or 3-phase. Three-phase is, however, preferable for reasons of safety and reliability. Current transformers with a secondary current of 1, 2 or 5 A are used for this purpose.Note: Current transformers for relay protection are preferable since they do not saturate as quickly as standard current transformers. The transformers should not saturate before at least twice the set over-current level.DetectorsDetector cables are available in standard lengths (see ordering details). They cannot be cut or joined. Avoid sharp bends or pinching when installing the cables. The plastic fiber is made of polymethylene acrylate (PMMA) with a polyethylene jacket . Each detector consists of an optical cable and a lens that are calibrated together to give the same sensitivity independent of cable length. The detector has a plug-in connector that fits the Arc monitor. The lens collects light from all directions, with the exception of a small shaded area behind the detector (see the polar diagram). Practical experiments have shown that arc light reflected between metallic surfaces is normally sufficient to cause tripping.Detector positioningThe basic strategy for positioning the sensors is to make sure to cover all parts that may suffer from an arc. Typically this involves the horizontal and vertical bus bar system and the breaker cubicle. If possible, it's also normally preferable to supervise each cubicle. Avoid placing the detector so that it sees the normal light from a breaker. The sensor can detect arcs within a 3-meter distance (see illustration). To raise the safety level even higher, you can separate them at a 1.5-meter distance, thereby creating redundancy between them.F11A1DQ1Arc Guard System™ with Arc monitorF11F21A1T1Q1Arc Guard System™ with Arc monitor and Current Sensing UnitA1 SwitchgearF11 Arc monitorF21 Current Sensing UnitT1 Current transformerQ1 Circuit-breakerPolar diagram of detectorExample showing the position of detectors in:1. Horizontal and vertical bus bar system2. Circuit-breaker cubicle
