ABB RELION Series Technical Manual page 632

Section 9
Control functions
626
synchronism are not detected. This function is also used to prevent the reconnection
of two systems which are divided after islanding and a three-pole reclosing.
The Synchro check function block includes both the synchronism check function and
the energizing function to allow closing when one side of the breaker is dead.
Network and the generator running in parallel with the network are connected through
the line AB. When a fault occurs between A and B, the protection relay protection
opens the circuit breakers A and B, thus isolating the faulty section from the network
and making the arc that caused the fault extinguish. The first attempt to recover is a
delayed autoreclosure made a few seconds later. Then, the autoreclose function
DARREC gives a command signal to the synchrocheck function to close the circuit
breaker A. SECRSYN performs an energizing check, as the line AB is de-energized
(U_BUS> Live bus value, U_LINE< Dead line value). After verifying the line AB is
dead and the energizing direction is correct, the protection relay energizes the line
(U_BUS -> U_LINE) by closing the circuit breaker A. The PLC of the power plant
discovers that the line has been energized and sends a signal to the other synchrocheck
function to close the circuit breaker B. Since both sides of the circuit breaker B are live
(U_BUS > Live bus value, U_LINE > Live bus value), the synchrocheck function
controlling the circuit breaker B performs a synchrocheck and, if the network and the
generator are in synchronism, closes the circuit breaker.
A
U_Bus
SECRSYN
DARREC
GUID-27A9936F-0276-47A1-B646-48E336FDA95C V2 EN
Figure 323: Synchrocheck function SECRSYN checking energizing conditions
and synchronism
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
U_Line U_Line
1MRS758755 A
G
B
U_Bus
SECRSYN
PLC
REC615 and RER615
Technical Manual