ABB RER620 Technical Manual page 338

Section 5
Control functions
332
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 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 SDARREC gives a command
signal to the synch-check function to close the circuit breaker A. SECRSYN performs an
energizing check, as the line AB is de-energized (V_BUS> Live bus value, V_LINE<
Dead line value). After verifying the line AB is dead and the energizing direction is
correct, the relay energizes the line (V_BUS -> V_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 synch-check function to close the circuit breaker B. Since both sides of the
circuit breaker B are live (V_BUS > Live bus value, V_LINE > Live bus value), the
synch-check function controlling the circuit breaker B performs a synch-check and, if the
network and the generator are in synchronism, closes the circuit breaker.
Figure 175: Synch-check function SECRSYN checking energizing conditions and
synchronism
Connections
A special attention is paid to the connection of the relay. Further, it is checked that the
primary side wiring is correct.
A faulty wiring of the voltage inputs of the relay causes a malfunction in the synch-check
function. If the wires of an energizing input have changed places, the polarity of the input
voltage is reversed (180°). In this case, the 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 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 relay
has to be close to zero within the permitted accuracy tolerances. The measured phase
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RER620
Technical Manual