Live/Dead Indication; Figure 4.9.8-1 Close On Zero Function; Figure 4.9.8-2 Close On Zero Timing - Siemens Argus 7SR21 Technical Manual

Slip Within Range ?
(> Split Slip & < COZ slip)
SLIP
COZ Slip Frequency Setting
Phase Difference
F
Angle
Phase Decreasing
CB Close Time
Live Line
Live Bus
Line U / V
Block
Bus U/ V
BLock
D
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: -

4.10 Live/Dead Indication

Outputs are provided to identify each voltage input as either Live or Dead using voltage user settings. These
outputs are controlled independently of the 25 Check Synchronising Voltage monitoring elements but operate in
the same way.
Voltage detectors are provided for each phase input A, B, C & X and inputs Y & Z when fitted. If the voltage on
the respective input is below a set threshold level they can be considered to be 'dead'. If the voltages are above a
voltage setting they are classed as 'live'. Independent voltage detectors are provided for both line and bus.
If a voltage is in the dead band range then it will be classed as dead until it has reached the live band area.
Similarly, if a voltage is live, it continues to be live until it has reached the dead band area. This effectively allows
for variable amounts of hysteresis to be set. Figure 4.10-1 illustrates the voltage detector operation.
Note: the area between the dead and live zones is not indeterminate. When any voltage is applied to the relay it
will ramp up the software RMS algorithm and always pass through the dead zone first.
A wide range is provided for live and dead voltage detector levels but the live and dead zones must not overlap.
Unrestricted ©2018 Siemens Protection Devices Limited
Split Slip Setting
&
?
Block
Block
Block
Figure 4.9.8-1
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0 200 400
CB Close Time (ms)
Figure 4.9.8-2
7SR210 & 7SR220 Description of Operation
&
&
Close On Zero Function
600 800
Close On Zero Timing
&
COZ
Close
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