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.
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
9.4.3.5 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.
Section 9 1MRK 506 369-UUS -
Current protection
514 Line distance protection REL670 2.2 ANSI
Application manual
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