Hitachi Relion 650 Series Technical Manual page 304

Section 12
Monitoring
Similarly, based on the changeover of NO and NC contacts, the mechanical moving time is evaluated
as the time gap between the instant of NO changeover and the instant of NC changeover as shown
in Table
Table 274: Derivation of the mechanical moving time for closing from NO and NC changeover timestamps
auxPosAvailable
None
NO only
NC only
NO and NC
where,
MMT= Measured mechanical moving time
t = Actual NC changeover time
NC
t = Actual NO changeover time
NO
Open operation mechanical monitoring
As per the physical design of the breaker, every opening operation is associated with a changeover
pattern of the 52a (NO) and 52b (NC) auxiliary contacts, as shown in
changeover of the auxiliary contacts always occurs on the same point of the travel curve, this allows
a simple monitoring of the mechanical opening operations of the CB.
298
274.
Mechanical moving time
0.0
0.0
0.0
MMT= t – t
NO
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NC
1MRK 511 557-UEN Rev. A
GUID-FE52FD6F-7B1D-4DE7-B8D9-306F2E116329 v2
Figure 139. Assuming that
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