Siemens 7SR224 Technical Manual page 338

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Figure 4.3-2 Typical System Interconnections showing Normally Open (TIE) Points and LOV Action Delay
timer grading margins.
An LOV close is blocked by the Block Reclose input in the same way as any autoreclose close. The setting of the
Block Reclose Delay should be considered in the setting of the LOV timing.
The LOV function is set to 'Out' by default and must be switched 'In'. The voltages and open/closed state of the
recloser is checked when an attempt is made to switch the function 'In'. A type Feeder or Recloser must be
Closed with voltage present on at least 1 side. A type NOP(Tie) must be Open with Live voltage on both sides.
This condition must be retained for the LOV Primed Time before the 'primed' staus is achieved. The device must
be in the 'primed' state for loss of voltage to start any LOV Action. The enable/disable setting LOV Primed
Interlock can be used to disable the voltage check but the relevant open/closed state is still required. The
NOP(Tie) device includes a LOV Memory Time which provides a reset delay for the primed condition when
voltage conditions of dead both sides is applied. This allows for the fact that during a fault the voltage on the
unfaulted side may be depressed by the proximity of the fault.
The devices can be set to start the LOV sequence from loss of voltage on either all three phases or loss of
voltage on any single phase. The single phase option can be used to restore load on a system where single pole
tripping is permitted.
The LOV system can be set to operate as a single or multi-shot sequence. When selected as Single mode, the
LOV Automation function will be automatically switched Out following a successful or unsuccessful LOV
sequence and the LOV In signal must be raised by the operator before a further sequence will be executed
following a subsequent loss of voltage.
©2010 Siemens Protection Devices Limited
LOV ACTION Delay = XX Seconds
85 s
1st
75 s
80 s
2nd 3rd
85 s 85 s
1st
75 s
80 s
2nd
3rd
85 s
1st
75 s
OFF
2nd
85 s
1st
75 s
80 s
2nd
7SR224 Argus Applications
80 s
75 s
Chapter 7 Page 39 of 50
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