Toshiba GRZ100 B Series, Instruction Manual, Page: 146 / 447

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3.1.2 Transformer Module
The transformer module (VCT module) provides isolation between the internal and external AC
circuits through an auxiliary transformer and transforms the magnitude of AC input signals to suit
the electronic circuits. The AC input signals are as follows:
•
three-phase currents (Ia, Ib and Ic)
•
residual current (3 I0)
•
residual current of parallel line (3 I0m)
•
three-phase voltages (Va, Vb and Vc)
•
autoreclose reference voltage (Vs1)
•
autoreclose reference voltage (Vs2)
Figure 3.1.2.1 shows a block diagram of the transformer module. There are 5 auxiliary CTs
mounted in the transformer module, and 4 or 5 auxiliary VTs depending on the relay model. (The
relationship between the relay model and number of AC input signals, is given in Table 3.2.1.1.)
"3I0m" in Figure 3.1.2.1 is the residual current from the parallel line in a double-circuit line, and is
used for mutual coupling compensation. Vs1 and Vs2 are the busbar or line voltages necessary for
the voltage and synchronism check for the autoreclose.
The transformer module is also provided with an IRIG-B port. This port collects the serial IRIG-B
format data from the external clock for synchronization of the relay calendar clock. The IRIG-B
port is insulated from the external circuit by a photo-coupler. A BNC connector is used as the input
connector.
Transformer module
IRIG-B port
BNC connector
I a
I b
I c
3I o
3I om
V a
V b
V c
External
clock
Signal
processing
module
Vs1
Vs2
Figure 3.1.2.1 Transformer Module