Siemens 7SR224 - Section 3: Supervision Functions; 3.1 CB Fail (50 BF)

7SR224 Argus Description of Operation
Phase Within Range ?
AND
Phase Decreasing ?
SLIP
Line U/V
Block
Bus U/V
BLock
V Block
Δ
Phase Angle Setting
&
Slip Frequency Setting
Block
Block
Block
&
Slip Timer
Setting
Slip Timer
Φ
Angle
Slip Within Range ?
SystemSync
Close
Live Line
Live Bus
Figure 4.3-3 System Sync Function
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.
Phase Difference &
Phase Decreasing ?
SLIP
Line U
/V
Block
Bus U
/V
BLock
V Block
Δ
&
COZ Slip Frequency Setting
Block
Block
Block
&
CB Close Time
Φ
Angle
Slip Within Range ?
COZ
Close
&
(> Split Slip & < COZ slip)
Split Slip Setting
Live Line
Live Bus
Figure 4.3-4 Cloze On Zero Function
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
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 200 400 600 800
CB Close Time (ms)
Maximum Slip Frequency (Hz)
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