Emax Low voltage air circuit-breakers - ABB Download Center

Notes:(1) In accordance also with IEC 60255-3Standard.(2) The current values above which G isdisabled are indicated in the installationmanual.Protection functionsThe PR123 trip unit offers the following protection functions:– overload (L) (1) ,– selective short-circuit (S),– instantaneous short-circuit (I),– earth fault with adjustable delay (G) (2) ,– directional short-circuit with adjustable delay (D),– phase unbalance (U),– protection against overtemperature (OT),– load control (K),– undervoltage (UV),– overvoltage (OV),– residual voltage (RV),– reverse power (RP),– underfrequency (UF),– overfrequency (OF),– phase sequence (alarm only).In addition to PR122/P features, the following improvements are available:Double selective short-circuit protection SIn addition to the standard S protection, PR123/P makes contemporarily available a secondtime-constant S protection (excludible) that allows two thresholds to be set independently achievingan accurate selectivity even under highly critical conditions.4Double earth fault protection GWhile in PR122/P the user must choose among the implementation of G protection throughinternal current sensors (calculating the vectorial sum of currents) or external toroid (directearth fault current measuring), PR123/P offers the exclusive feature of the contemporaneousmanagement of both the configuration, by means of two independent earth fault protectionscurves. The main application of this characteristic is simultaneous activation of restricted andunrestricted earth fault protection. See chapter 6 for details.Directional short-circuit protection with adjustable delay DThe protection works in a similar way to the fixed-time protection “S”, with the added ability torecognize the direction of the phases current during the fault period.The current direction makes it possible to determine whether the fault is on the supply or loadside of the circuit-breaker. Particularly in ring distribution systems, this makes it possible to identifyand disconnect the distribution segment where the fault has occurred, whilst keeping the restof the installation running. If multiple PR122 or PR123 trip units are used, this protection can beassociated with zone selectivity.Residual current protection RcWith PR123/P is possible to have the residual current protection only adding the external toroid(1SDA063869).ABB SACE 4/25