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Section 9
Current protection
9.4.3.4
480
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.
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
harmonic restrain blocking, will give 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
1MRK 506 369-UEN B
nd
Line distance protection REL670 2.2 IEC
Application manual
M15282-106 v4
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