System Split Detector; System Sync Reversion - Siemens Argus 7SR21 Technical Manual

4.9.5

System Split Detector

A system split occurs where part of the system becomes islanded and operates separately. Under these
conditions the frequencies of the voltages either side of the breaker are asynchronous and therefore high phase
angle differences can occur as the voltage phasors slip past each other.
The decision to change to System Split settings, apply Close on Zero function, Lockout or ignore, during
autoreclose and manual closing is set separately by the 25 DAR Split Mode and 25 MC Split Mode settings. The
System Split condition is detected when either the measured phase difference angle exceeds the pre-set 25 Slip
Angle value or if the slip frequency exceeds a pre-set 25 Split Slip rate based on the selection of 25 System
Split Mode setting.
Note : the system split setting is effectively an absolute value and therefore a split will occur at the value
regardless of the direction of the frequency slip e.g. if an angle of 170° is selected, then starting from 0°, a split
will occur at +170° or -170° (effectively +190°).
If a system split occurs during an autoreclose Check Sync operation, with 25 System Sync set to Enabled, the
following events occur: -
·
A System Split event is recorded.
·
If the 25 DAR Split Mode is set to CS, Check Sync will continue.
·
If the 25 DAR Split Mode setting has been set to SS, the System Sync function is started.
The 25 SS In Progress can be mapped to an output relay or led for alarm indication. The
mapped LED will stay on for a minimum time, or can be latched using non self reset LEDs.
·
If the 25 DAR Split Mode setting has been set to COZ, the Close On Zero function is started.
The 25 COZ In Progress can be mapped to an output relay or led for alarm indication.
·
If the 25 DAR Split Mode has been set to LO, then, a 25 System Split LO output is given
which can be mapped to an output relay or led for alarm indication. The relay will stay in this
lockout mode until one of the following methods of resetting it is performed: -
·
1. The relay is reset from Lockout by binary input or a command.
·
2. The CB is manually closed
Similarly if a system split occurs during a Manual Close Check Sync operation, with 25 System Sync set to
Enabled, the following events occur: -
·
A System Split event is recorded.
·
If the 25 MC Split Mode is set to CS, Check Sync will continue.
·
If the 25 MC Split Mode setting has been set to SS, the System Sync function is started. The
25 SS In Progress can be mapped to an output relay or led for alarm indication.
·
If the 25 DAR Split Mode setting has been set to COZ, the Close On Zero function is started.
The 25 COZ In Progress can be mapped to an output relay or led for alarm indication.
4.9.6

System Sync Reversion

If the close conditions of System Sync are not met and a zero slip condition is subsequently detected, by the slip
falling below the 25 Split Slip setting, the relay will exit from System Sync mode and revert to Check
Synchronising mode. The reversion allows the device to use the wider Check Sync parameters, to allow a close
following the restoration of normal operation when the islanded network has been reconnected to the main
network by successful reclosure of a parallel connection.
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7SR210 & 7SR220 Description of Operation
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