Connections
A special attention is paid to the connection of the protection relay. Furthermore it
is checked that the primary side wiring is correct.
A faulty wiring of the voltage inputs of the protection relay causes a malfunction in
the synchrocheck function. If the wires of an energizing input have changed places,
the polarity of the input voltage is reversed (180°). In this case, the protection relay
permits the circuit breaker closing in a situation where the voltages are in opposite
phases. This can damage the electrical devices in the primary circuit. Therefore, it is
extremely important that the wiring from the voltage transformers to the terminals
on the rear of the protection relay is consistent regarding the energizing inputs
U_BUS (bus voltage) and U_LINE (line voltage).
The wiring should be verified by checking the reading of the phase difference
measured between the U_BUS and U_LINE voltages. The phase difference measured
by the protection relay has to be close to zero within the permitted accuracy
tolerances. The measured phase differences are indicated in the LHMI. At the
same time, it is recommended to check the voltage difference and the frequency
differences presented in the monitored data view. These values should be within the
permitted tolerances, that is, close to zero.
Figure 852
shows an example where the synchrocheck is used for the circuit breaker
closing between a busbar and a line. The phase-to-phase voltages are measured
from the busbar and also one phase-to-phase voltage from the line is measured.
Figure 852: Connection of voltages for the protection relay and signals used in
synchrocheck
9.5.7 Signals
1MRS759142 F
Control functions
REX640
Technical Manual
1553
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