ABB RELION Series Technical Manual page 633

1MRS758755 A
REC615 and RER615
Technical Manual
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 324 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.
GUID-DE29AFFC-9769-459B-B52C-4C11DC37A583 V3 EN
Figure 324: Connection of voltages for the protection relay and signals used in
synchrocheck
Section 9
Control functions
627