ABB Relion 670 Series Applications Manual page 136

Section 8
Current protection
Power System
ANSI05000136 V1 EN-US
Figure 59: 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.
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.
8.2.3.4 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
from step 4. The 2
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.
130
51N 51N
en05000136_ansi.vsd
nd
harmonic restrain will prevent unwanted operation in case of transformer
© Copyright 2017 Hitachi Power Grids. All rights reserved
nd
harmonic restrain signal will latch as long as the
nd
harmonic restrain blocking, will give operation
1MRK 511 407-UUS Rev. J
M15282-106 v5
Phasor measurement unit RES670
Application manual