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2.35.2 VCHK1 and VCHK2 for 1.5CB system
(i) Characteristic and elements
VCHK1 and VCHK2 are used for verification of existence or non-existence of voltage on 1.5CB
system. As shown in Figure 2.35-3(b), VCHK2 is used in the center CB (CB#2). Four elements
(OVL2, UVL2, OVL, and UVL) are configured for VCHK2; they are used for determination of
existence or non-existence of voltage.
(ii) Voltage condition and check zone
Figure 2.35-3(a) shows that VCHK1 checks the presence of voltage between the Bus-bar and
Line; Figure 2.35-3(b) shows that the VCHK2 checks the presence of voltage between Line2
and Line. The result of the VCHK1 and VCHK2 are shown in Table 2.35-3 and Table 2.35-4,
respectively. Sync check is carried out if the result by VCHK1 is B1 zone and if the result by
VCHK2 is B2 zone.
A1, C1, D1: Voltage check
B1: Synchronism check
V
L
Line voltage
(Incoming voltage)
V
B
Bus-bar voltage
(Running voltage)
Dead bus and
dead line
(DB-DL)
Dead bus and
live line
(DB-LL)
Live bus and
live line
(LB-LL)
Live bus and
dead line
(LB-DL)
A2, C2, D2: Voltage check
B2: Synchronism check
V
L
Line voltage
(Incoming voltage)
V
L2
Line2 voltage
(Running voltage)
Dead line and
dead line2
(DL2-DL)
Live line and
dead line2
(DL2-LL)
Live line and
live line2
(LL2-LL)
Dead line and
Live line2
(LL2-DL)
Figure 2.35-3 Check zones by VCHK1 and VCHK2
Table 2.35-3 Voltage condition by VCHK1
Table 2.35-4 Voltage condition by VCHK2
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