The fuse supervision is connected to ULN1OK-ULN1FF, ULN2OK-ULN2FF and
with alternative Healthy or Failing MCB signals depending on what is available from
each MCB.
The tie circuit breaker is connected either to bus 1 or line 1 voltage on one side and the
other side is connected either to bus 2 or line 2 voltage. Four different output
combinations are possible, bus to bus, bus to line, line to bus and line to line.
• The line 1 voltage is selected if the line 1 disconnector is closed.
• The bus 1 voltage is selected if the line 1 disconnector is open and the bus 1 circuit
breaker is closed.
• The line 2 voltage is selected if the line 2 disconnector is closed.
• The bus 2 voltage is selected if the line 2 disconnector is open and the bus 2 circuit
breaker is closed.
The function also checks the fuse-failure signals for bus 1, bus 2, line 1 and line 2. If
a VT failure is detected in the selected voltage an output signal USELFAIL is set. This
output signal is true if the selected bus or line voltages have a MCB trip. This output
as well as the function can be blocked with the input signal BLOCK. The function
block diagram for the voltage selection of a bus circuit breaker is shown in figure
167
and for the tie circuit breaker in figure 168.
Section 12 1MRK 502 048-UEN A
Control
334
Technical manual
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