Close On Zero Mode; Figure 4.3-3 System Sync Function; Figure 4.3-4 Cloze On Zero Function - Siemens 7SR224 Technical Manual

SLIP Slip Within Range ?
Slip Frequency Setting
Phase Within Range ?
Φ
Angle AND
Phase Decreasing ?
Phase Angle Setting
Live Line
Live Bus
Line U/V
Block
Bus U/V
BLock
Δ
V Block
4.3.9

Close on Zero Mode

If the 25 DAR Split Mode or 25 MC Split Mode is set to COZ the relay will apply a Close On Zero to the respective
closing operation if the synchronising mode changes to System Split. The measured slip frequency and the
measured phase difference are used to provide a Close Pulse which will close the CB when the phase difference
is reducing and timed with the setting 25 CB Close Time such that the instant of closure is when the phase
difference is zero. The slip frequency must be less than the 25 COZ Slip Freq but greater than the 25 Split Slip
setting to avoid reversion to Check Synchronising conditions.
Since this feature is part of the System Synchronising function, 25 System Sync must also be set to Enabled.
Slip Within Range ?
(> Split Slip & < COZ slip)
SLIP
Split Slip Setting
COZ Slip Frequency Setting
Phase Difference &
Φ
Angle
Phase Decreasing ?
CB Close Time
Live Line
Live Bus
Line U/ V
Block
Bus U/ V
BLock
Δ
V Block
Close on Zero will not be accurate if slow CB times are applied in conjunction with fast slip rates during testing.
Practical application limits are shown below
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0 200
CB Close Time (ms)
©2010 Siemens Protection Devices Limited
Slip Timer
Slip Timer
&
Block
Block
Block
Figure 4.3-3 System Sync Function
&
&
Block
Block
Block
Figure 4.3-4 Cloze On Zero Function
400 600 800
7SR224 Argus Description of Operation
&
SystemSync
Setting
&
COZ
Close
Close
Chapter 1 Page 51 of 70