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1MRK 505 370-UEN D
UseStartValue : Gives which current level should be used for the activation of the blocking
signal. This is given as one of the settings of the steps: Step 1/2/3/4. Normally, the step
having the lowest operation current level should be set.
7.3.2.4
Switch onto fault logic
In case of energizing a faulty object there is a risk of having a long fault clearance time, if the
fault current is too small to give fast operation of the protection. The switch on to fault
function can be activated from auxiliary signals from the circuit breaker, either the close
command or the open/close position (change of position).
This logic can be used to issue a fast trip if one breaker pole does not close properly at a
manual or automatic closing.
SOTF and under time are similar functions to achieve fast clearance at asymmetrical closing
based on requirements from different utilities.
The function is divided into two parts. The SOTF function will give operation from step 2 or 3
during a set time after change in the position of the circuit breaker. The SOTF function has a
set time delay. The under time function, which has 2
operation from step 4. The 2nd harmonic restrain will prevent unwanted function in case of
transformer inrush current. The under time function has a set time delay.
Below the settings for switch on to fault logics are described.
SOTF : This parameter can be set: Off/SOTF/Under Time/SOTF+Under Time .
ActivationSOTF : This setting will select the signal to activate SOTF function; CB position
open/CB position closed/CB close command .
StepForSOTF : If this parameter is set on step 3, the step 3 start signal will be used as current
set level. If set on step 2, the step 2 start signal will be used as current set level.
HarmBlkSOTF : This is used to On / Off harmonic restrain during SOTF conditions.
tSOTF : Time delay for operation of the SOTF function. The setting range is 0.000 - 60.000 s in
step of 0.001 s. The default setting is 0.100 s
t4U : Time interval when the SOTF function is active after breaker closing. The setting range is
0.000 - 60.000 s in step of 0.001 s. The default setting is 1.000 s.
ActUnderTime : Describes the mode to activate the sensitive undertime function. The function
can be activated by Circuit breaker position (change) or Circuit breaker command.
tUnderTime : Time delay for operation of the sensitive undertime function. The setting range is
0.000 - 60.000 s in step of 0.001 s. The default setting is 0.300 s
7.3.2.5
Settings for each step (x = 1, 2, 3 and 4)
Operation : Sets the protection to On or Off .
DirModex : The directional mode of step x . Possible settings are Off / Non-directional / Forward /
Reverse .
Characteristx : Selection of time characteristic for step x . Definite time delay and different
types of inverse time characteristics are available.
Inverse time characteristic enables fast fault clearance of high current faults at the same time
as selectivity to other inverse time phase overcurrent protections can be assured. This is
Busbar protection REB670
Application manual
nd
harmonic restrain blocking, will give
Section 7
Current protection
M15282-106 v4
M15282-9 v12
163
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