lags by 330 degrees the high-voltage-side phasor. The rotation of the phasors is
counterclockwise.
The generic rule is that a low-voltage-side phasor lags the high-voltage-side phasor
by clock number * 30º. This is called angle difference adjustment and can be set for
SECRSYN with the
Phase shift
setting.
9.5.6 Application
The main purpose of the synchrocheck function is to provide control over the
closing of the circuit breakers in power networks to prevent the closing if the
conditions for 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.
G
SECRSYN
DARREC
SECRSYN
PLC
A
B
U_Bus U_BusU_Line U_Line
Figure 851: Synchrocheck function SECRSYN checking energizing conditions and
synchronism
Control functions
1MRS759142 F
1552 REX640
Technical Manual
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