One necessary component in the fault clearance system is the circuit breaker. It is frompractical and economical reason not feasible to duplicate the circuit breaker for theprotected component. Instead a breaker failure protection is used.The Breaker failure protection, phase segregated activation and output (CSPRBRF 50BF)issues a back-up trip command to adjacent circuit breakers in case of failure to trip of the“normal” circuit breaker for the protected component. The detection of failure to break thecurrent through the breaker is made by means of current measurement or as detection ofremaining trip signal (unconditional).CSPRBRF (50BF) can also give a re-trip. This means that a second trip signal is sent to theprotected circuit breaker. The re-trip function can be used to increase the probability ofoperation of the breaker, or it can be used to avoid back-up trip of many breakers in caseof mistakes during relay maintenance and test.7.11.3 Setting guidelinesThe parameters for Breaker failure protection, phase segregated activation and outputCSPRBRF (50BF) are set via the local HMI or PCM600.The following settings can be done for the breaker failure protection, phase segregatedactivation and output. Common base IED values for primary current (IBase), primaryvoltage (VBase) and primary power (setting SBase) are set in a Global base values forsettings function GBASVAL. Setting GlobalBaseSel is used to select a GBASVALfunction for reference of base values.Operation: Disabled/EnabledFunctionMode: This parameter can be set Current/Contact. This states the way thedetection of failure of the breaker is performed. In the mode current the currentmeasurement is used for the detection. In the mode Contact the long duration of breakerposition signal is used as indicator of failure of the breaker. The mode Current&Contactmeans that both ways of detections are activated. Contact mode can be usable inapplications where the fault current through the circuit breaker is small. This can be thecase for some generator protection application (for example reverse power protection) orin case of line ends with weak end infeed.RetripMode: This setting states how the re-trip function shall operate. Retrip Off meansthat the re-trip function is not activated. CB Pos Check (circuit breaker position check) andCurrent means that a phase current must be larger than the operate level to allow re-trip.CB Pos Check (circuit breaker position check) and Contact means re-trip is done whencircuit breaker is closed (breaker position is used). No CB Pos Check means re-trip is donewithout check of breaker position.Section 7 1MRK 506 334-UUS ACurrent protection234Application manual
