Switch Onto Fault Logic - ABB REG670 Applications Manual

Section 9
Current protection
9.4.3.4
9.4.3.5
344

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
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
Settings for each step (x = 1, 2, 3 and 4)
Operation: Sets the protection to On or Off.
DirModex: The directional mode of step x. Possible settings are Off/Non-directional/
Forward/Reverse.
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
1MRK 502 071-UEN -
nd
harmonic
Application manual