7.6.2 Application M13916-3 v7In the design of the fault clearance system the N-1 criterion is often used. Thismeans that a fault needs to be cleared even if any component in the fault clearancesystem is faulty. One necessary component in the fault clearance system is thecircuit breaker. It is from practical and economical reason not feasible to duplicatethe circuit breaker for the protected object. Instead a breaker failure protection isused.Breaker failure protection, 3-phase activation and output (CCRBRF) will issue aback-up trip command to adjacent circuit breakers in case of failure to trip of the“normal” circuit breaker for the protected object. The detection of failure to breakthe current through the breaker is made by means of current measurement or asdetection of remaining trip signal (unconditional).CCRBRF 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 theprobability of operation of the breaker, or it can be used to avoid back-up trip ofmany breakers in case of mistakes during relay maintenance and testing.7.6.3 Setting guidelines M11546-4 v9The parameters for Breaker failure protection 3-phase activation and outputCCRBRF are set via the local HMI or PCM600.The following settings can be done for the breaker failure protection.GlobalBaseSel: Selects the global base value group used by the function to defineIBase, UBase and SBase as applicable.Operation: Off/OnFunctionMode This parameter can be set Current or Contact. This states the waythe detection 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 ofbreaker position signal is used as indicator of failure of the breaker. The modeCurrent/Contact means that both ways of detections are activated. Contact modecan be usable in applications where the fault current through the circuit breaker issmall. This can be the case for some generator protection application (for examplereverse power protection) or in case of line ends with weak end infeed.RetripMode: This setting states how the re-trip function shall operate. Retrip Offmeans that the re-trip function is not activated. CB Pos Check (circuit breakerposition check) and Current means that a phase current must be larger than theoperate level to allow re-trip. CB Pos Check (circuit breaker position check) andContact means re-trip is done when circuit breaker is closed (breaker position isused). No CBPos Check means re-trip is done without any check of breakerposition.1MRK 504 169-UEN A Section 7Current protectionTransformer protection RET650 2.2 IEC 137Application manual
