exceeds the
Current dead Lin Val
setting, the SOTF situation is signalled to SOTF
control module after the set
Cur voltage Det time
.
SOTF control
The SOTF control module needs to be activated before the operation is possible
in the switch-onto-fault situation. There are two ways to activate the SOTF control
module.
• By CB_CL_CMD (circuit breaker closing command).
• By the dead line condition received from the dead line detection module.
Dead line detection should be used only when the voltage transformers
are located on the line side of the circuit breaker.
When the CB_CL_CMD input is activated or the dead line condition is detected, the
SOTF control module becomes active. The reset timer is started when CB_CL_CMD
is inactivated or the dead line condition disappears. Thus, the module becomes
inactive after the set
SOTF reset time
is exceeded.
When the SOTF control module is active, the
Operation mode
setting defines the
operation criteria for the detection of a switch-onto-fault condition. The detection
can be based on the external start signals from the distance or overcurrent
functions, on the measured internal voltage and current levels, or on both.
Table 1168: Options for SOTF detection
Operation mode Description
Start
The OPERATE output is activated immediately after a signal
from the trigger module. This indicates that the breaker is
closed onto fault.
Current & Voltage
The OPERATE output is activated immediately after a signal
from the SOTF detection module. This indicates that the
breaker is closed onto fault. This operation mode can be
used, for example, if the non-directional distance zone is not
available.
Both
The OPERATE output is activated immediately after a signal
from the trigger or SOTF detection modules. This indicates
that the breaker is closed onto fault.
The OPERATE output can be blocked by activating the BLOCK input.
5.8.6 Application
The operation of CVPSOF is generally based on the non-directional distance zone or
the non-directional overcurrent stage. When the feeder-side voltage transformers
are used for providing the polarization quantity for the distance or directional
overcurrent protection, the use of non-directional impedance or current based
protection for starting CVPSOF secures a fast switch-onto-fault tripping in the
close-in three-phase short circuits. The non-directional protection provides a fast
fault clearance when the protection is used for energizing a bus from the feeder
with a short circuit fault in it. Other protection functions, like time delayed zero-
sequence overcurrent functions, can be connected to CVPSOF to increase the
dependability of the scheme. The other main advantage of using CVPSOF is that it
Protection related functions
1MRS759142 F
1226 REX640
Technical Manual
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