ABB 615 series Technical Manual page 993

1MAC059074-MB A
615 series ANSI
Technical Manual
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 V_BUS (bus voltage) and V_LINE
(line voltage).
The wiring should be verified by checking the reading of the phase difference measured
between the V_BUS and V_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 501 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.
Section 9
Control functions
987