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 802: 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.
5.6.5
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
typically accelerates the tripping in case of energizing a feeder onto a fault. Without
CVPSOF, this tripping is normally performed by the normal time-graded protection
or alternatively by the time-delayed local backup protection, for which operating
times are considerably longer than with CVPSOF tripping.
An internal dead line detection check is provided to activate the function when the
voltage transformers are located on the feeder side. An initiation by the dead line
detection is highly recommended for the busbar configurations where more than
one circuit breaker at one feeder end can energize the protected feeder or the
feeder can also be energized from the other end.
Setting guidelines
Input
START
: If a distance zone is used for starting the switch-onto-fault function,
the zone has to be set to cover the entire protected feeder with a safety margin
of minimum 20 percent. If the non-directional zone is not available, the internal
Current & Voltage criterion or the start signal from the GFC function can be used
Protection related functions
1MRS757644 H
832
620 series
Technical Manual
