in the IED. Alternatively, the internal signals from fuse failure supervision can beused when available. There are two alternative connection possibilities. Inputslabelled OK must be connected if the available contact indicates that the voltagecircuit is healthy. Inputs labelled FF must be connected if the available contactindicates that the voltage circuit is faulty.The UB1OK/UB2OK and UB1FF/UB2FF inputs are related to the busbar voltageand the ULNOK and ULNFF inputs are related to the line voltage. Configure themto the binary input or function outputs that indicate the status of the external fusefailure of the busbar and line voltages. In the event of a fuse failure, the energizingcheck function is blocked. The synchronizing and the synchrocheck functionrequires full voltage on both sides and will be blocked automatically in the event offuse failures.11.1.7.7 Voltage selection for a single circuit breaker with double busbarsThis function uses the binary input from the disconnectors auxiliary contactsB1QOPEN-B1QCLD for Bus 1, and B2QOPEN-B2QCLD for Bus 2 to selectbetween bus 1 and bus 2 voltages. If the disconnector connected to bus 1 is closedand the disconnector connected to bus 2 is opened the bus 1 voltage is used. Allother combinations use the bus 2 voltage. The Outputs B1SEL and B2SELrespectively indicate the selected Bus voltage.The function checks the fuse-failure signals for bus 1, bus 2 and line voltagetransformers. Inputs UB1OK-UB1FF supervise the fuse for Bus 1 and UB2OK-UB2FF supervises the fuse for Bus 2. ULNOK -ULNFF supervises the fuse for theLine voltage transformer. The inputs fail (FF) or healthy (OK) can alternatively beused dependent on the available signal. If a fuse-failure is detected in the selectedvoltage source an output signal USELFAIL is set. This output signal is true if theselected bus or line voltages have a fuse failure. This output as well as the functioncan be blocked with the input signal BLOCK. The function logic diagram is shownin figure 147.Section 11 1MRK 502 034-UEN -Control290Technical Manual
