6.7.6 Monitored dataTable 71:CCRBRF (50BF) Monitored dataName Type Values (Range) Unit DescriptionI_A REAL - A Measured current in phase AI_B REAL - A Measured current in phase BI_C REAL - A Measured current in phase CIN REAL - A Measured residual current6.7.7 Operation principleBreaker failure protection, 3-phase activation and output CCRBRF (50BF) is initiatedfrom protection trip command, either from protection functions within the IED or fromexternal protection devices.The initiate signal is general for all three phases. A re-trip attempt can be made after a settime delay. The re-trip function can be done with or without CB position check based oncurrent and/or contact evaluation. With the current check the re-trip is only performed ifthe current through the circuit breaker is larger than the operate current level. With contactcheck the re-trip is only performed if breaker is indicated as closed.The initiate signal can be an internal or external protection trip signal. This signal willinitiate the back-up trip timer. If the opening of the breaker is successful this is detectedby the function, by detection of either low current through RMS evaluation and a specialadapted current algorithm or by open contact indication. The special algorithm enables avery fast detection of successful breaker opening, that is, fast resetting of the currentmeasurement. If the current and/or contact detection has not detected breaker openingbefore the back-up timer has run its time a back-up trip is initiated.Further the following possibilities are available:• In the current detection it is possible to use three different options: 1 out of 3 whereit is sufficient to detect failure to open (high current) in one pole, 1 out of 4 where itis sufficient to detect failure to open (high current) in one pole or high residual currentand 2 out of 4 where at least two current (phase current and/or residual current) shallbe high for breaker failure detection.• The current detection level for the residual current can be set different from the settingof phase current detection.• Back-up trip is always made with current or contact check. It is possible to have thisoption activated for small load currents only.1MRK 511 287-UUS A Section 6Current protection139Technical manual
