ABB RELION 670 Series Applications Manual page 174

Section 7
Current protection
Power System
ANSI05000136 V1 EN-US
Figure 87: Application for parallel transformer inrush current logic
BlkParTransf function is activated the 2
If the
residual current measured by the relay is larger than a selected step current level. Assume that
step 4 is chosen to be the most sensitive step of the four step residual overcurrent protection
function EF4PTOC (51N_67N). The harmonic restrain blocking is enabled for this step. Also the
same current setting as this step is chosen for the blocking at parallel transformer energizing.
Below the settings for the parallel transformer logic are described.
Use_PUValue : Gives which current level that should be used for 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.
BlkParTransf : This parameter can be set Disable / Enable , the parallel transformer logic.
7.3.2.5 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 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
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 operation mode : 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 .
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
168
51N 51N
en05000136_ansi.vsd
nd
harmonic restrain signal will latch as long as the
nd
harmonic restrain blocking, will give operation
1MRK 505 337-UUS A
M15282-106 v3
Application manual