The settings for the parallel transformer logic are described below.
BlkParTransf
: This is used to
Enable
blocking at energising of parallel transformers.
Use_PUValue
: 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
M15282-106 v4
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
nd
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:
Disabled/SOTF/Under Time/SOTF+Under Time
.
SOTFSel
: 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 pickup signal will be used as
current set level. If set on step 2, the step 2 pickup 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.
1MRK 505 370-UUS A
Section 7
Current protection
Busbar protection REB670 2.2 ANSI
201
Application manual
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