ABB Relion 670 Series Applications Manual page 158

Section 8
Current protection
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 : 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.
ActUndrTimeSel : 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
8.4.3.5 Settings for each step (x = 1, 2, 3 and 4)
Operation : Sets the protection to Enabled or Disabled .
DirModeSelx : The directional mode of step x . Possible settings are Disabled / 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 mainly used
in radial fed networks but can also be used in meshed networks. In meshed networks, the settings
must be based on network fault calculations.
To assure selectivity between different protections, in the radial network, there has to be a
minimum time difference Dt between the time delays of two protections. To determine the
shortest possible time difference, the operation time of protections, breaker opening time and
protection resetting time must be known. These time delays can vary significantly between
different protective equipment. The following time delays can be estimated:
Protection trip time:
Protection resetting time:
Breaker opening time:
152
15-60 ms
15-60 ms
20-120 ms
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nd
harmonic restrain blocking, will give operation
1MRK 511 401-UUS F
M15282-9 v12
Bay control REC670
Application manual