5.2.3 FunctionalityThe breaker failure function CCBRBRF is activated by trip commands from theprotection functions. The commands are either internal commands to the terminalor external commands through binary inputs. The start command is always adefault for three-phase operation. CCBRBRF includes a three-phase conditional orunconditional re-trip function, and also a three-phase conditional back-up tripfunction.CCBRBRF uses the same levels of current detection for both re-trip and back-uptrip. The operating values of the current measuring elements can be set within apredefined setting range. The function has two independent timers for trippurposes: a re-trip timer for the repeated tripping of its own breaker and a back-uptimer for the trip logic operation for upstream breakers. A minimum trip pulselength can be set independently for the trip output.The function contains a blocking functionality. It is possible to block the functionoutputs, if desired.5.2.4 Operation principleThe function can be enabled and disabled with the Operation setting. Thecorresponding parameter values are "On" and "Off".The operation of the breaker failure protection can be described using a modulediagram. All the modules in the diagram are explained in the next sections. Alsofurther information on the retrip and backup trip logics is given in sub-modulediagrams.TRRETBLOCKCB_FAULTTRBUBack-uptriplogicPOSCLOSESTARTIoRetriplogicLeveldetector2Leveldetector1I_AI_BI_CtTimer 2tTimer 3CB_FAULT_ALStartlogic tTimer 1A070445 V3 ENFigure 285: Functional module diagram. I_A, I_B and I_C represent phasecurrents and Io residual current.Section 5 1YHT530004D05 DProtection related functions542 615 seriesTechnical Manual
