Charge Delays; Voltage Monitoring Elements; Sync Override Logic; Figure 4.3-1 Voltage Detector Operation - Siemens 7SR224 Technical Manual

4.3.2

Charge Delays

Separate delay settings are provided for Dead Line Charge and Dead Bus Charge closure. These are applied
after the autoreclose Dead Time when voltage conditions are checked and met, at the Close Inhibit stage of the
sequence. This feature effectively allows the dead time to be set differently for faults on each side of the recloser.
4.3.3

Voltage monitoring elements

The single phase voltage source used for synchronising can be selected as any phase to phase or phase to earth
voltage for flexibility. The voltage is compared to the corresponding voltage from the three phase arrangement on
the other side of the circuit breaker. Voltage settings are set as a percentage of the nominal voltage specified in
the CT/VT Config menu.
Voltage detectors
Voltage detectors determine the status of the line or bus. If the voltages on either the line or bus are below a set
threshold level they can be considered to be 'dead'. If the voltages are within a setting band around the nominal
voltage 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 4.3-1 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.
Under-voltage detectors
The under-voltage detectors, if enabled, can block a close output command if either the line voltage or the bus
voltage is below the under-voltage setting value. Both line and bus have their own independent settings.
Differential voltage detectors
The differential voltage detector, if enabled, can block a close output command if the difference between the line
and bus voltages is greater than the differential voltage setting value.
4.3.4

Sync Override Logic

For certain switching operations, a means of bypassing the Check Synchronisation function is provided. This is
provided by separate binary inputs for 79 Override Sync and Man Override Sync.
©2010 Siemens Protection Devices Limited

Figure 4.3-1 Voltage Detector Operation

7SR224 Argus Description of Operation
Chapter 1 Page 48 of 70