Table 2: Evaluating isolator and circuit-breaker statusesReturn confirmation thatisolator/CB CLOSEDReturn confirmation thatisolator/CB OPENIsolator/CB imageinactive inactive Last status retained anddelayed for the bus image ofbusbar protection- isolator alarm- switch inhibit signalinactive active OPENactive inactive CLOSEDactive active CLOSED and delayed- isolator alarm- switch inhibit signalAn active CB CLOSE signal (CB CLOSE command) forces the circuit-breakers into theCLOSED position.7.2.4 Isolator alarm GUID-B89A10FC-29F9-4CD8-971A-B4C04CF67672 v1If the isolator and circuit-breaker supervision function detects an error, it is signaled on thelocal HMI and also via the output signal “Isolator alarm” after the set signal delay.7.2.5 Delay GUID-F496B6F3-7F7C-41C6-A927-82AE0EBB5521 v1Isolators require a certain time to operate and while they are in motion, the relationshipbetween the status signals and therefore the integrity of the isolator image may be brieflydisturbed due to the different points at which the auxiliary contacts are actuated. As this isquite normal, an isolator alarm should not be generated and therefore the alarm has to bedelayed.7.2.6 Blocking by the isolator alarm GUID-87197CE8-80B7-4E97-BB6F-A6150CA1DC0E v1If considered necessary, the isolator alarm can be arranged (set) to block the protection. Thereare two alternative settings:• Block protection Operation of the busbar protection and the intertripping system iscompletely blocked.• Discriminative blocking (preferred alternative) Operation of the busbar protection and theintertripping system is only blocked for the section of busbar (protection zone)concerned.7.2.7 Switch inhibit GUID-8BA04886-4DC8-4BC7-8986-3778A2ABF625 v1If the isolator alarm was initiated by an isolator or circuit-breaker that at the time determinedthe assignment of protection zones, the Switch inhibit signal is also set.Section 7 1MRK 505 399-UEN BSystem Settings32 Distributed busbar protection REB500Application manual© Copyright 2019 ABB. All rights reserved
