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2.35.6 Scheme and activation
VCHK1 and VCHK2 provide output signals to the ARC with results of voltage check and
synchronism check as described earlier. The energizing control scheme of VCHK1 is drawn in
Figure 2.35-10, the output signal ARC1-VCHK is fed to ARC1 when one or more of the
following conditions are established: (1) the VCHK1 runs, (2) the OVB and the UVL run, or (3)
the UVB and the OVL run. The activation of VCHK1 is controlled by using the scheme
switches: [ARC1-LB_DL], [ARC1-DB_LL], [ARC1-DB_DL], and [ARC1-SYN1]. For example,
DB_LL in Table 2.35-2 is only the criteria for ARC1 operation, On is set for the scheme switch
[ARC1-DB_LL] while Off is set for other scheme switches. As a result, the system is energized
in the direction from line to bus with ARC1. As shown in Figure 2.35-11, the operation of the
VCHK2 is also applicable in accordance with Figure 2.35-3 similar to VCHK1. Note that the
SYN1-df and SYN2-df operations are nullified when Off are set for the [SYN1-dfEN] and
[SYN2-dfEN].
Figure 2.35-10 Logic of VCHK1
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