14000006-IEC18000483-1-en.vsdxIEC18000483 V1 EN-USFigure 57: Example 4: Enabling tripping by the BBP function without VTs on the busbars11.1.4.2 Solution GUID-9BC30C0D-B060-4750-82E5-4899E91CA85C v2The settings are the same as in example 3.REB500 evaluates all the VTs assigned to the respective protection zone (seeTechnicalManual). Assignment takes place via the intertripping logic, that is, it depends on the statusesof the isolators. Tripping is only enabled when all the voltage functions assigned to theprotection zone in question generate an enabling signal (AND logic).This means that an overvoltage function cannot enable tripping of the protection zone shouldthe voltage be interrupted either due to a tripped m.c.b. or an open-circuit.This means that an undervoltage function will enable tripping of the protection zone shouldthe voltage be interrupted either due to a tripped m.c.b. or an open-circuit. Since, however, theother undervoltage functions assigned to the protection zone are also evaluated; they preventtripping from taking place.An interruption of the VT circuit can be detected in the case of an undervoltagefunction by supervising the bay unit output signal 28805_Voltage criterion orthe central unit output signal 48805_Voltage criterion.By activating the input signal 18205_Fuse failure superv. UV a tripped m.c.b.can be configured to enable tripping of the respective protection zone in thecase of an overvoltage function.REB500 is thus able derive the voltage on the busbars, even if there are no VTs to measure itdirectly. Tripping of a protection zone to which no VTs are assigned (for example, all theisolators open) is enabled by the voltage function.11.1.4.3 Result GUID-5BFFF8E9-F824-430E-854B-B6375234292C v2In the event of a fault on a given busbar section (for example, BB1), the busbar protectionfunction for BB1 trips. A fault on a busbar section will normally cause a voltage collapse, which1MRK 505 399-UEN B Section 11Additional protection featuresDistributed busbar protection REB500 85Application manual© Copyright 2019 ABB. All rights reserved
